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Default Interference in FM radio reception.

AFAIK, nothing around here has changed, but in the last 3 months I
have been getting intermittent but strong interference in my FM radio
reception, and I'd like to find the source and stop it. .

I'm usually in bed when I notice this, and today for the first time, I
was able to get to two other radios and I saw the same interference
was on both of them for the same frequency, but it wasn't on the
Intenet version of same station.

It can last from 10 seconds to over an hour. It can be continuous or
go off and on occasionally, with off-periods that also vary in
length.. It sounds sort of like a fog horn, but a somewhat higher
pitch. Or the horn on a diesel locamotive. Or a steady note on a
trumpet. Except it often doesn't end as suddenly as they do, but
might have little noises for a second or two at the end. (I can't
remember how to describe the sound at the end.)

The sound can be medium or loud. That is, sometimes I can sort of
hear the radio program, usually talk, in addition to the noise. Other
times the noise overwhelms the program and I have no idea what they
are saying..

It affects 90.1 and 88.5 Mhz, either one and sometimes both. Both of
these stations normally come in perfectly. I live in Baltimore, and
these are DC stations, WAMU and WCSP, which is C-Span radio, (which is
broadcast only from DC). I haven't found it on 88.1 and afaicr
itdoesn't show up on frequencies much higher than 90.1.

It happens in the middle of the night some times, or today at noon, or
it seems any time.

My nearest neighbor said she wasn't home during one episode, but I
have otther townhouse neigbhbors farther away.

Any suggestions what the source of this might be?

Thanks for any help.
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Default Interference in FM radio reception.

micky wrote:
AFAIK, nothing around here has changed, but in the last 3 months I
have been getting intermittent but strong interference in my FM radio
reception, and I'd like to find the source and stop it. .


The Russians have resurrected a souped-up version of The Russian Woodpecker
(Wikipedia that)! (AKA "Steelyard")

TRW was sited very close (~10km) to the nuclear power station at Pripyat,
near Chernobyl.

Now the whole area is overgrown with trees, but the antenna array still
stands.

And interestingly, as a westerner, I had assumed it was way north of where
I am, but actually, Pripyat/Steelyard are on almost exactly the same latitude
as my hometown in Kent (south-east England)!

I heard TRW on the radio when I was a kid. There was a documentary on TV
about it at the time.

As for your FM problem, sorry, to be honest, I don't know. But if you find out,
let us know here; I'd be interested to read what it was.


Martin
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Default Interference in FM radio reception.

In article ,
micky wrote:

AFAIK, nothing around here has changed, but in the last 3 months I
have been getting intermittent but strong interference in my FM radio
reception, and I'd like to find the source and stop it. .

I'm usually in bed when I notice this, and today for the first time, I
was able to get to two other radios and I saw the same interference
was on both of them for the same frequency, but it wasn't on the
Intenet version of same station.

It can last from 10 seconds to over an hour. It can be continuous or
go off and on occasionally, with off-periods that also vary in
length.. It sounds sort of like a fog horn, but a somewhat higher
pitch. Or the horn on a diesel locamotive. Or a steady note on a
trumpet. Except it often doesn't end as suddenly as they do, but
might have little noises for a second or two at the end. (I can't
remember how to describe the sound at the end.)


What you are describing, sounds somewhat to me as if it may be what
amateur-radio operators refer to as "doubling" - the result of two
signals of somewhat similar strength, on the same or near-by FM
frequencies at the same time. On ham 2-meter transmissions it often
has a characteristic "growling" sound. If one of the two signals is
significantly stronger than the other, you may hear the music or voice
from that signal, but in many cases neither transmission can be heard
clearly.

The sound can be medium or loud. That is, sometimes I can sort of
hear the radio program, usually talk, in addition to the noise. Other
times the noise overwhelms the program and I have no idea what they
are saying..

It affects 90.1 and 88.5 Mhz, either one and sometimes both. Both of
these stations normally come in perfectly. I live in Baltimore, and
these are DC stations, WAMU and WCSP, which is C-Span radio, (which is
broadcast only from DC). I haven't found it on 88.1 and afaicr
itdoesn't show up on frequencies much higher than 90.1.


If I had to guess, I'd guess that there's somebody in your
neighborhood operating some sort of local-area FM transmitter. This
might be:

- A "broadcast your CD player music throughout the house" device, or

- a "feed music from your CD player or iPod, through FM, into your
car radio which doesn't have a direct input" device, or

- a full-fledged "pirate radio" station, or

- a legitimately-licensed "micropower" FM station (there are a few
although it's not at all easy to get a license), or

- some sort of malfunctioning device, in or near your house, which is
oscillating out of control and generating spurious frequency
carriers. Fluorescent light ballasts, electronic heaters,
defective house wiring, and computer-network gear can all do this.

In all of these cases (except possibly the licensed micropower
station) the offending transmission ought to be shut down, as (1) it's
interfering, (2) on a frequency it shouldn't be on, (3) without a
license.

It's also possible that your radios are being interfered with, by a
perfectly legal (but high-powered) transmission from a nearby
source... police or fire radio transmitter, ham radio, etc. Cases
like this are usually the result of something called "fundamental
overload" or "strong signal overload", and they are usually *not* the
legal fault or responsibility of whoever is transmitting. They are
(the FCC declares) the result of poor design of the receiving radio
(e.g. yours) - it's not adequately shielded or filtered - and it'd be
your responsibility to fix your radio. However, from the fact that
you're hearing the problem only on certain frequencies, while others
higher on the band are not affected, I don't think that this is the
case in your situation.

The fact that you're hearing it on multiple radios, gives you a pretty
good assurance that it's not just a single malfunctioning radio. Are
all of these radios powered from the AC mains, or are all of them
battery radios, or have you heard it on some of each type?

As to locating the source... well, you're probably in for an exercise
in radio direction finding! There are quite a variety of ways to
trace down the location of a transmission... some require lots of
equipment, some require as little as a small battery-powered portable
radio and a Pringles can covered in aluminum foil (the "body fade")
method.

A practical suggestion: see if you can locate one or more amateur
radio clubs in your area. Within the ham community, there are a fair
number of hams who enjoy "foxhunting" (radio-direction-finding
contests, looking for hidden transmitters), and others who have a very
specific interest in hunting for RF interferences sources and for
illegal transmitters (some of the ARRL "official observer" volunteers
have teams who do this). You may be able to locate some folks who
would be willing to come out, with some of their direction-finding
equipment, and help you locate the source of the interfering
transmission.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
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Default Interference in FM radio reception.


"micky"

AFAIK, nothing around here has changed, but in the last 3 months I
have been getting intermittent but strong interference in my FM radio
reception, and I'd like to find the source and stop it. .

I'm usually in bed when I notice this, and today for the first time, I
was able to get to two other radios and I saw the same interference
was on both of them for the same frequency, but it wasn't on the
Intenet version of same station.

It can last from 10 seconds to over an hour. It can be continuous or
go off and on occasionally, with off-periods that also vary in
length.. It sounds sort of like a fog horn, but a somewhat higher
pitch. Or the horn on a diesel locamotive. Or a steady note on a
trumpet. Except it often doesn't end as suddenly as they do, but
might have little noises for a second or two at the end. (I can't
remember how to describe the sound at the end.)

The sound can be medium or loud. That is, sometimes I can sort of
hear the radio program, usually talk, in addition to the noise. Other
times the noise overwhelms the program and I have no idea what they
are saying..

It affects 90.1 and 88.5 Mhz, either one and sometimes both. Both of
these stations normally come in perfectly. I live in Baltimore, and
these are DC stations, WAMU and WCSP, which is C-Span radio, (which is
broadcast only from DC). I haven't found it on 88.1 and afaicr
itdoesn't show up on frequencies much higher than 90.1.

It happens in the middle of the night some times, or today at noon, or
it seems any time.

My nearest neighbor said she wasn't home during one episode, but I
have otther townhouse neigbhbors farther away.


** You will need to get a portable FM radio and walk about with it to find
where the source is.

Anecdotes:

1. Once had spike noise interference visible on the scope on my workbench -
it began in the early evening and was at a very steady rate of once in 6
seconds. On a portable AM radio, the clicking noise was very clear. I
tracked it down to a small, flashing, red neon sign in the window of a
pharmacy 60 metres away.

2. Had interference on TV at about the same time, visible only on VHF
channel 2 ( 63 to 70 MHz) - the colour would drop out regularly ( every 5 -
10 seconds ) and noise bands appeared. The problem was only there during the
day on work days.

Turned out to be a RF plastic welding machine on 27.12 MHz in a factory 200
metres away. The particular TV was known to be vulnerable to CB radio when
tuned to channel 2.

3. High frequency RF suddenly appeared on my scope one day while doing
testing at full sensitivity ( 5mV /div). It disappeared after 15 minutes but
then returned the next day. Turing up the time base speed showed it to be a
steady signal on 29 to 30MHz.

Switched on my radio scanner and soon found that my upstairs neighbours had
bought themselves a cordless telephone transmitting both ends on the
conversation on 30.15 MHz.


.... Phil



















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Default Interference in FM radio reception.

Cell towers around here Akron ohio rent tower space to different radio or
RF links they put their dish or arrays on the towers that have been alot of
RFI problems just thinking that maybe its the cause of the interference
problems



"Phil Allison" wrote in message
...

"micky"

AFAIK, nothing around here has changed, but in the last 3 months I
have been getting intermittent but strong interference in my FM radio
reception, and I'd like to find the source and stop it. .

I'm usually in bed when I notice this, and today for the first time, I
was able to get to two other radios and I saw the same interference
was on both of them for the same frequency, but it wasn't on the
Intenet version of same station.

It can last from 10 seconds to over an hour. It can be continuous or
go off and on occasionally, with off-periods that also vary in
length.. It sounds sort of like a fog horn, but a somewhat higher
pitch. Or the horn on a diesel locamotive. Or a steady note on a
trumpet. Except it often doesn't end as suddenly as they do, but
might have little noises for a second or two at the end. (I can't
remember how to describe the sound at the end.)

The sound can be medium or loud. That is, sometimes I can sort of
hear the radio program, usually talk, in addition to the noise. Other
times the noise overwhelms the program and I have no idea what they
are saying..

It affects 90.1 and 88.5 Mhz, either one and sometimes both. Both of
these stations normally come in perfectly. I live in Baltimore, and
these are DC stations, WAMU and WCSP, which is C-Span radio, (which is
broadcast only from DC). I haven't found it on 88.1 and afaicr
itdoesn't show up on frequencies much higher than 90.1.

It happens in the middle of the night some times, or today at noon, or
it seems any time.

My nearest neighbor said she wasn't home during one episode, but I
have otther townhouse neigbhbors farther away.


** You will need to get a portable FM radio and walk about with it to find
where the source is.

Anecdotes:

1. Once had spike noise interference visible on the scope on my
workbench - it began in the early evening and was at a very steady rate of
once in 6 seconds. On a portable AM radio, the clicking noise was very
clear. I tracked it down to a small, flashing, red neon sign in the
window of a pharmacy 60 metres away.

2. Had interference on TV at about the same time, visible only on VHF
channel 2 ( 63 to 70 MHz) - the colour would drop out regularly ( every
5 - 10 seconds ) and noise bands appeared. The problem was only there
during the day on work days.

Turned out to be a RF plastic welding machine on 27.12 MHz in a factory
200 metres away. The particular TV was known to be vulnerable to CB radio
when tuned to channel 2.

3. High frequency RF suddenly appeared on my scope one day while doing
testing at full sensitivity ( 5mV /div). It disappeared after 15 minutes
but then returned the next day. Turing up the time base speed showed it to
be a steady signal on 29 to 30MHz.

Switched on my radio scanner and soon found that my upstairs neighbours
had bought themselves a cordless telephone transmitting both ends on the
conversation on 30.15 MHz.


... Phil























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Default Interference in FM radio reception.

On Thu, 05 Jan 2012 17:59:54 -0500, micky
wrote:

It sounds sort of like a fog horn, but a somewhat higher
pitch. Or the horn on a diesel locamotive. Or a steady note on a
trumpet. Except it often doesn't end as suddenly as they do, but
might have little noises for a second or two at the end. (I can't
remember how to describe the sound at the end.)

The sound can be medium or loud. That is, sometimes I can sort of
hear the radio program, usually talk, in addition to the noise. Other
times the noise overwhelms the program and I have no idea what they
are saying..


(...)
Any suggestions what the source of this might be?


Good description but not enough to identify the culprit. It doesn't
sound like a heterodyne and there's no indication of any additional
voice or music modulation making intermod an unlikely cause. If you
could record an MP3 audio clip and post it somewhere, it would be a
big help.

FM noise is fairly uncommon. FM was originally designed to ignore
amplitude modulated noise, which it does quite well. However, with
the introduction of HDFM, the digital modulation scheme included AM
components. The result is the sensitivity to AM interference has
increased. The noise description does not sound familiar so this is
unlikely. However, I'm curious if the unspecified maker and model
receiver is and HDFM receiver and were you possibly listening to HD1
or HD2.

Also, try a different FM receiver. If both radios receive the same
interference, then its probably being radiated over the air or
conducted on the power lines. However, if only one radio hears the
interference on the same channel, then it's possible that there's
something wrong with the receiver or the noise is being generated in
the radio.

Also, your description sound vaguely like RFI from a plasma TV. The
level, modulation characteristics, and frequency will vary with what
is on the screen. The timing pattern you describe sounds roughly like
a TV being turned on and off at random times. Do the times when it's
on coincide with prime time TV?

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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Default Interference in FM radio reception.

On Jan 5, 4:59*pm, micky wrote:
AFAIK, nothing around here has changed, but in the last 3 months I
have been getting intermittent but strong interference in my FM radio
reception, and I'd like to find the source and stop it. .

I'm usually in bed when I notice this, and today for the first time, I
was able to get to two other radios and I saw the same interference
was on both of them for the same frequency, but it wasn't on the
Intenet version of same station.

It can last from 10 seconds to over an hour. *It can be continuous or
go off and on occasionally, with off-periods that also vary in
length.. * It sounds sort of like a fog horn, but a somewhat higher
pitch. * Or the horn on a diesel locamotive. * Or a steady note on a
trumpet. * *Except it often doesn't end as suddenly as they do, but
might have little noises for a second or two at the end. *(I can't
remember how to describe the sound at the end.)

The sound can be medium or loud. *That is, sometimes I can sort of
hear the radio program, usually talk, in addition to the noise. *Other
times the noise overwhelms the program and I have no idea what they
are saying..

It affects 90.1 and 88.5 Mhz, either one and sometimes both. *Both of
these stations normally come in perfectly. * *I live in Baltimore, and
these are DC stations, WAMU and WCSP, which is C-Span radio, (which is
broadcast only from DC). *I haven't found it on 88.1 and afaicr
itdoesn't show up on frequencies much higher than 90.1.

It happens in the middle of the night some times, or today at noon, or
it seems any time.

My nearest neighbor said she wasn't home during one episode, but I
have otther townhouse neigbhbors farther away.

Any suggestions what the source of this might be?

Thanks for any help.


Portable FM radio, listen for the original noise, then walk around the
neighborhood.
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Default Interference in FM radio reception.

On Thu, 05 Jan 2012 17:59:54 -0500, micky
wrote:

AFAIK, nothing around here has changed, but in the last 3 months I
have been getting intermittent but strong interference in my FM radio
reception, and I'd like to find the source and stop it. .



First I'm going to find my MP3 player, which has an FM radio, and try
to circle in on the source of the noise. I didn't think the problem
could be so far away, so it's good that I'm looking farther now. .

There are two big ham radio clubs around here, and smaller ones in
adjacent counties. I go to their hamfests all the time. A few of
them even know me. The problem now is that I haven't kept a log of
when the interference occurs, so even if they're willing, I can't tell
them when to come over. I'll keep the log, and I'll call them
anyhow. Maybe one who likes foxhunting lives 5 minutes away, etc.

I plan to get back to you with more details when I know them, but it
may take a while.

BTW, the two stations I mentioned are HD, so Jeff, maybe that's why
they get the noise. So is 88.1, which is very close to 88.5 of
course, but 88.1 is a local station, not 45 miles away, so maybe its
signal is too strong for this interference to interfere????


Thaks for all the good advice.

P.S. There are also one or two buses that park 100 to 150 yards
from my house. Maybe they have some fancy new electronics. They have
an erratic schedule themselves, in that I thought there was never more
than one and it only parked unitl i's next route began. Maybe 10
minutes, but I've been paying attention and it's more complicated.
Al;so I live in the suburbs and didn't think they ran all night, but
next time the noise starts in the night I'll force myself to the
window to look. (Obviously I'm awake, but I don't like sitting up.)
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Default Interference in FM radio reception.

Jeff Liebermann wrote in message
...
On Thu, 05 Jan 2012 17:59:54 -0500, micky
wrote:

It sounds sort of like a fog horn, but a somewhat higher
pitch. Or the horn on a diesel locamotive. Or a steady note on a
trumpet. Except it often doesn't end as suddenly as they do, but
might have little noises for a second or two at the end. (I can't
remember how to describe the sound at the end.)

The sound can be medium or loud. That is, sometimes I can sort of
hear the radio program, usually talk, in addition to the noise. Other
times the noise overwhelms the program and I have no idea what they
are saying..


(...)
Any suggestions what the source of this might be?


Good description but not enough to identify the culprit. It doesn't
sound like a heterodyne and there's no indication of any additional
voice or music modulation making intermod an unlikely cause. If you
could record an MP3 audio clip and post it somewhere, it would be a
big help.

FM noise is fairly uncommon. FM was originally designed to ignore
amplitude modulated noise, which it does quite well. However, with
the introduction of HDFM, the digital modulation scheme included AM
components. The result is the sensitivity to AM interference has
increased. The noise description does not sound familiar so this is
unlikely. However, I'm curious if the unspecified maker and model
receiver is and HDFM receiver and were you possibly listening to HD1
or HD2.

Also, try a different FM receiver. If both radios receive the same
interference, then its probably being radiated over the air or
conducted on the power lines. However, if only one radio hears the
interference on the same channel, then it's possible that there's
something wrong with the receiver or the noise is being generated in
the radio.

Also, your description sound vaguely like RFI from a plasma TV. The
level, modulation characteristics, and frequency will vary with what
is on the screen. The timing pattern you describe sounds roughly like
a TV being turned on and off at random times. Do the times when it's
on coincide with prime time TV?

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558




I've no idea if it would work but can you make a portable FM receiver
directional by placing in a metal tube? Perhaps with a metal plate under a
shoe with a grounding wire. Would have to be speaker output , so an earpiece
did not fed RF down




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On Sat, 7 Jan 2012 08:50:51 -0000, "N_Cook" wrote:

I've no idea if it would work but can you make a portable FM receiver
directional by placing in a metal tube?


Not really. The tube would need to be about 1/2 wavelength long
(about 1.5 meters) and would totally block the signal. If you run a
1/4 wave lengthwise slit down the length of the tube, you would be
able to hear something (at reduced sensitivity). However, it wouldn't
be very directional. I've built rotating tube type direction finders
using this principle, but at 2.4Ghz, where the size of the antenna is
more practical.

Perhaps with a metal plate under a
shoe with a grounding wire. Would have to be speaker output , so an earpiece
did not fed RF down


You can stop the earpiece from becoming an antenna with a simple
ferrite bead at the EP jack.

Much of what you suggest has already been done by hams for transmitter
hunts.
http://www.homingin.com
There's quite a bit of existing equipment available that will work.
Something cheap and crude are the various "homer" type direction
finders. Also known as TDOA (time difference of arrival).
http://www.handi-finder.com
http://www.arrl.org/direction-finding
http://www.dxzone.com/catalog/Operating_Modes/Radio_Direction_Finding/
etc..

AN/SRD-21 homer type direction finder manual (4.5MB)
http://802.11junk.com/jeffl/AN-SRD-21/ANSRD-21%20manual.pdf

Much of the technology use for the 2meter (145Mhz) ham band is
directly applicable to the 88-108 band if scaled. Unfortunately, all
the problems and headaches are also applicable (interference from
other stations, reflections, insufficient directionality, antenna side
lobes, etc).

Direction finding on the FM broadcast band is problematic because of
the potential for interference from adjacent channel stations. The FM
receiver IF bandwidth usually slops into the adjacent channels. In
the US, we have 200KHz channels, with allocations every alternate
channel. This reduces the problem, but doesn't eliminate it. In EU,
it's on 100KHz channels, possibly with alternate channel allocations.

However, methinks all this is overkill for finding a noise source. The
first thing I would do is turn off the power to the house, except for
the FM receiver. Many noise sources are conducted (through the power
lines) rather than radiated (over the air). If the noise goes away,
it's coming from something in the house. From there, it's just a
matter of turning off breakers until the location is isolated. Then,
turn off individual pieces of equipment. I've found an amazing
assortment of noise sources this way. If killing the power doesn't
find it, ask the neighbors to do the same (while carrying a portable
FM receiver). You'll be amazed at how many consumer devices generate
disgusting levels of RFI/EMI. From the description, the 10 sec to 1
hr duration is an important clue. That points to a thermostat, air
flow, or water demand operated device. It might also be an electric
heater. Killing the house power should be able to isolate it.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


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Default Interference in FM radio reception.

On Thu, 05 Jan 2012 17:59:54 -0500, micky
wrote:

AFAIK, nothing around here has changed, but in the last 3 months I
have been getting intermittent but strong interference in my FM radio
reception, and I'd like to find the source and stop it. .

I'm usually in bed when I notice this, and today for the first time, I
was able to get to two other radios and I saw the same interference
was on both of them for the same frequency, but it wasn't on the
Intenet version of same station.

It can last from 10 seconds to over an hour. It can be continuous or
go off and on occasionally, with off-periods that also vary in
length.. It sounds sort of like a fog horn, but a somewhat higher
pitch. Or the horn on a diesel locamotive. Or a steady note on a
trumpet. Except it often doesn't end as suddenly as they do, but
might have little noises for a second or two at the end. (I can't
remember how to describe the sound at the end.)

The sound can be medium or loud. That is, sometimes I can sort of
hear the radio program, usually talk, in addition to the noise. Other
times the noise overwhelms the program and I have no idea what they
are saying..

It affects 90.1 and 88.5 Mhz, either one and sometimes both. Both of
these stations normally come in perfectly. I live in Baltimore, and
these are DC stations, WAMU and WCSP, which is C-Span radio, (which is
broadcast only from DC). I haven't found it on 88.1 and afaicr
itdoesn't show up on frequencies much higher than 90.1.

It happens in the middle of the night some times, or today at noon, or
it seems any time.

My nearest neighbor said she wasn't home during one episode, but I
have otther townhouse neigbhbors farther away.

Any suggestions what the source of this might be?

Thanks for any help.

One thing that strikes me about this is the random (erratic?) nature
of this interference, varying both in time and duration. To me, that
rules out many devices - common home appliances, factory equipment,
radio transmitters, etc. One thing that does operate on a similar
pattern is a telephone. Is it possibly a cordless telephone operating
on an oddball frequency?

PlainBill
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Default Interference in FM radio reception.

On Sat, 07 Jan 2012 14:39:02 -0700, wrote:

One thing that strikes me about this is the random (erratic?) nature
of this interference, varying both in time and duration. To me, that
rules out many devices - common home appliances, factory equipment,
radio transmitters, etc. One thing that does operate on a similar
pattern is a telephone. Is it possibly a cordless telephone operating
on an oddball frequency?


Think about something run by a thermostat, low control switch, or
motion detector. They tend to cycle erratically. Things like a
furnace, electric heater, water pressure boost pump, pool heater,
demand water heater, sump pump, etc. There are also some uncommon
devices that cycle. Negative ion generator, parking lot light
controller, external HDD or NAS boxes, motion detector operated
devices, iPhone background sync, etc.

However, I've been fooled before with this pattern. I was looking for
such things, only to discover that the interference was coming from a
microwave oven at a local eatery. During lunch, the microwave ovens
were in use almost constantly. At other times, a minute or so at a
time. Kinda sounds like the original description.

Dumb story: Many years ago, I had a very difficult time trying to
find the source of short bursts of RFI. I tried for days and failed.
Oddly, the interference seemed wide spread and appeared almost
everywhere that I was sniffing. Eventually, the gears that drive my
brain engaged and I discovered that the Motorola Bravo pager that I
was carrying at the time, was the source. Argh.

--
Jeff Liebermann

150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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Jeff Liebermann wrote:
On Sat, 7 Jan 2012 08:50:51 -0000, "N_Cook" wrote:

I've no idea if it would work but can you make a portable FM receiver
directional by placing in a metal tube?


Not really. The tube would need to be about 1/2 wavelength long
(about 1.5 meters) and would totally block the signal. If you run a
1/4 wave lengthwise slit down the length of the tube, you would be
able to hear something (at reduced sensitivity). However, it wouldn't
be very directional. I've built rotating tube type direction finders
using this principle, but at 2.4Ghz, where the size of the antenna is
more practical.

Perhaps with a metal plate under a
shoe with a grounding wire. Would have to be speaker output , so an earpiece
did not fed RF down


You can stop the earpiece from becoming an antenna with a simple
ferrite bead at the EP jack.

Much of what you suggest has already been done by hams for transmitter
hunts.
http://www.homingin.com
There's quite a bit of existing equipment available that will work.
Something cheap and crude are the various "homer" type direction
finders. Also known as TDOA (time difference of arrival).
http://www.handi-finder.com
http://www.arrl.org/direction-finding
http://www.dxzone.com/catalog/Operating_Modes/Radio_Direction_Finding/
etc..

AN/SRD-21 homer type direction finder manual (4.5MB)
http://802.11junk.com/jeffl/AN-SRD-21/ANSRD-21%20manual.pdf

Much of the technology use for the 2meter (145Mhz) ham band is
directly applicable to the 88-108 band if scaled. Unfortunately, all
the problems and headaches are also applicable (interference from
other stations, reflections, insufficient directionality, antenna side
lobes, etc).

Direction finding on the FM broadcast band is problematic because of
the potential for interference from adjacent channel stations. The FM
receiver IF bandwidth usually slops into the adjacent channels. In
the US, we have 200KHz channels, with allocations every alternate
channel. This reduces the problem, but doesn't eliminate it. In EU,
it's on 100KHz channels, possibly with alternate channel allocations.

However, methinks all this is overkill for finding a noise source. The
first thing I would do is turn off the power to the house, except for
the FM receiver. Many noise sources are conducted (through the power
lines) rather than radiated (over the air). If the noise goes away,
it's coming from something in the house. From there, it's just a
matter of turning off breakers until the location is isolated. Then,
turn off individual pieces of equipment. I've found an amazing
assortment of noise sources this way. If killing the power doesn't
find it, ask the neighbors to do the same (while carrying a portable
FM receiver). You'll be amazed at how many consumer devices generate
disgusting levels of RFI/EMI. From the description, the 10 sec to 1
hr duration is an important clue. That points to a thermostat, air
flow, or water demand operated device. It might also be an electric
heater. Killing the house power should be able to isolate it.



You can use an fm radio with a full length antenna. It will register in two
directions used horizontally. Some broad band harmonics are best tracked
down going from the lower freqs to higher. I tracked down some fm
interference driving my car up and Down street. Strong interference near my
house. It's all these cheap led switching current regulators I am using. I
still have not tried to filter the outputs. I got wiring all over the
place.

Greg
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On Sat, 7 Jan 2012 23:23:05 +0000 (UTC), gregz
wrote:

Jeff Liebermann wrote:
On Sat, 7 Jan 2012 08:50:51 -0000, "N_Cook" wrote:

I've no idea if it would work but can you make a portable FM receiver
directional by placing in a metal tube?


Not really. The tube would need to be about 1/2 wavelength long
(about 1.5 meters) and would totally block the signal. If you run a
1/4 wave lengthwise slit down the length of the tube, you would be
able to hear something (at reduced sensitivity). However, it wouldn't
be very directional. I've built rotating tube type direction finders
using this principle, but at 2.4Ghz, where the size of the antenna is
more practical.

Perhaps with a metal plate under a
shoe with a grounding wire. Would have to be speaker output , so an earpiece
did not fed RF down


You can stop the earpiece from becoming an antenna with a simple
ferrite bead at the EP jack.

Much of what you suggest has already been done by hams for transmitter
hunts.
http://www.homingin.com
There's quite a bit of existing equipment available that will work.
Something cheap and crude are the various "homer" type direction
finders. Also known as TDOA (time difference of arrival).
http://www.handi-finder.com
http://www.arrl.org/direction-finding
http://www.dxzone.com/catalog/Operating_Modes/Radio_Direction_Finding/
etc..

AN/SRD-21 homer type direction finder manual (4.5MB)
http://802.11junk.com/jeffl/AN-SRD-21/ANSRD-21%20manual.pdf

Much of the technology use for the 2meter (145Mhz) ham band is
directly applicable to the 88-108 band if scaled. Unfortunately, all
the problems and headaches are also applicable (interference from
other stations, reflections, insufficient directionality, antenna side
lobes, etc).

Direction finding on the FM broadcast band is problematic because of
the potential for interference from adjacent channel stations. The FM
receiver IF bandwidth usually slops into the adjacent channels. In
the US, we have 200KHz channels, with allocations every alternate
channel. This reduces the problem, but doesn't eliminate it. In EU,
it's on 100KHz channels, possibly with alternate channel allocations.

However, methinks all this is overkill for finding a noise source. The
first thing I would do is turn off the power to the house, except for
the FM receiver. Many noise sources are conducted (through the power
lines) rather than radiated (over the air). If the noise goes away,
it's coming from something in the house. From there, it's just a
matter of turning off breakers until the location is isolated. Then,
turn off individual pieces of equipment. I've found an amazing
assortment of noise sources this way. If killing the power doesn't
find it, ask the neighbors to do the same (while carrying a portable
FM receiver). You'll be amazed at how many consumer devices generate
disgusting levels of RFI/EMI. From the description, the 10 sec to 1
hr duration is an important clue. That points to a thermostat, air
flow, or water demand operated device. It might also be an electric
heater. Killing the house power should be able to isolate it.



You can use an fm radio with a full length antenna. It will register in two
directions used horizontally. Some broad band harmonics are best tracked
down going from the lower freqs to higher. I tracked down some fm
interference driving my car up and Down street.


I have to check out my car radio too. I haven't heard any
interference on it, but like I say, it comes at various times. often
from 2 to 9 in the morning (and I don't commute regularly, and even
when I do, I'm only in the car near my house for a couple minutes.)

Strong interference near my
house. It's all these cheap led switching current regulators I am using. I
still have not tried to filter the outputs. I got wiring all over the
place.


It's the curse of the electronics age.

Greg


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On Sat, 07 Jan 2012 14:51:23 -0800, Jeff Liebermann
wrote:

On Sat, 07 Jan 2012 14:39:02 -0700, wrote:

One thing that strikes me about this is the random (erratic?) nature
of this interference, varying both in time and duration. To me, that
rules out many devices - common home appliances, factory equipment,
radio transmitters, etc. One thing that does operate on a similar
pattern is a telephone. Is it possibly a cordless telephone operating
on an oddball frequency?


Think about something run by a thermostat, low control switch, or
motion detector. They tend to cycle erratically. Things like a
furnace,


The furnace would correspond to the end of the night, and the
beginning of the morning, which are common times for this. . At the
end of the night, it's cold for the night thermostat setting, and at
the beginning of the morning, it has to get hotter yet.

In some ways my neighbors are very friendly. Most will answer the
door at 9PM. OTOH, when I asked a couple to see how their new furnace
was installed, they looked at me strange.

I wouldn't have nerve enough, as someone suggested, to ask one to turn
off all his power, certainly not unless I had narrowed it down to his
house.

electric heater, water pressure boost pump, pool heater,
demand water heater, sump pump, etc.


Definitely does this even when there hasn't been any rain. I'm
literally the lowest house in the n'hood**, and would have heard my
sump pump when I was hearing the basement radio make the noise.

**And the way it works out, it's 200 yards or more to any house
outside the n'hood, all of which are also higher than I am. .

There are also some uncommon
devices that cycle. Negative ion generator, parking lot light
controller, external HDD or NAS boxes, motion detector operated
devices, iPhone background sync, etc.


Dang, I only rejected one from your whole list.

However, I've been fooled before with this pattern. I was looking for
such things, only to discover that the interference was coming from a
microwave oven at a local eatery. During lunch, the microwave ovens
were in use almost constantly. At other times, a minute or so at a
time. Kinda sounds like the original description.


Maybe I should go look for lights on when it does this in the middle
of the night. That's one thing I might do.

Dumb story:


There are no dumb questions or dumb stories. Only dumb people.

:~) Oops, I shouldn't bite the hand that feeds me. :~)

Many years ago, I had a very difficult time trying to
find the source of short bursts of RFI. I tried for days and failed.
Oddly, the interference seemed wide spread and appeared almost
everywhere that I was sniffing. Eventually, the gears that drive my
brain engaged and I discovered that the Motorola Bravo pager that I
was carrying at the time, was the source. Argh.




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On Sat, 07 Jan 2012 01:19:27 -0500, micky
wrote:

There are two big ham radio clubs around here, and smaller ones in
adjacent counties.


The hams can be very helpful if properly approached. Much depends on
the available time, talent, experience, and hardware.

BTW, the two stations I mentioned are HD, so Jeff, maybe that's why
they get the noise. So is 88.1, which is very close to 88.5 of
course, but 88.1 is a local station, not 45 miles away, so maybe its
signal is too strong for this interference to interfere????


I can't tell from here. The problem is that the occupied bandwidth of
an FM station with HD1 and HD2 sub-carriers is more than the assigned
bandwidth:
http://www.ham-radio.com/k6sti/hdrsn.htm
Just read the first two sections, as the rest is all about fixing the
resultant noise.

Reminder: Please make an MP3 sound clip of the noises.
http://www.dxzone.com/catalog/Internet_and_Radio/Sounds/

Identifying Sources of Radio Frequency Interference Around the Home
"http://randombio.com/interference.html"

Hint: Assumption is the mother of all screwups. Test your theories
and guesswork, even if you think it's improbable. I've been wrong and
surprised more times than I can comfortably admit. That's one reason
my domain is called LearnByDestroying.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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On Sat, 07 Jan 2012 21:46:01 -0800, Jeff Liebermann
wrote:

On Sat, 07 Jan 2012 01:19:27 -0500, micky
wrote:

There are two big ham radio clubs around here, and smaller ones in
adjacent counties.


The hams can be very helpful if properly approached. Much depends on
the available time, talent, experience, and hardware.

BTW, the two stations I mentioned are HD, so Jeff, maybe that's why
they get the noise. So is 88.1, which is very close to 88.5 of
course, but 88.1 is a local station, not 45 miles away, so maybe its
signal is too strong for this interference to interfere????


I can't tell from here. The problem is that the occupied bandwidth of
an FM station with HD1 and HD2 sub-carriers is more than the assigned
bandwidth:
http://www.ham-radio.com/k6sti/hdrsn.htm
Just read the first two sections, as the rest is all about fixing the
resultant noise.

Reminder: Please make an MP3 sound clip of the noises.


That will take me some time. I first have to find my Sanza Chip, or
Clip,or whatever it's called. It does record iirc. I've been sort
of looking for it for months, but now I have a reason to look harder.

The radio next to the computer has reception problems with these
stations, so the noise is muffled and only recognizeable because I
heard it on the other radios. Tonight I tried to fix up two AM/FM
clock radios, but only got the AM working on each.

I also have a 40 year old cassette recorder that probably works fine,
unless it doesn't I guess I coudl use that and then play it for the
computer mike. (I have a great computer mike. )

http://www.dxzone.com/catalog/Internet_and_Radio/Sounds/

Identifying Sources of Radio Frequency Interference Around the Home
"http://randombio.com/interference.html"


I'll check these all out.

Hint: Assumption is the mother of all screwups. Test your theories
and guesswork, even if you think it's improbable. I've been wrong and
surprised more times than I can comfortably admit. That's one reason
my domain is called LearnByDestroying.


LOL. Okay. I'll do my best.
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On Sat, 07 Jan 2012 14:51:23 -0800, Jeff Liebermann
wrote:

On Sat, 07 Jan 2012 14:39:02 -0700, wrote:

One thing that strikes me about this is the random (erratic?) nature
of this interference, varying both in time and duration. To me, that
rules out many devices - common home appliances, factory equipment,
radio transmitters, etc. One thing that does operate on a similar
pattern is a telephone. Is it possibly a cordless telephone operating
on an oddball frequency?


Think about something run by a thermostat, low control switch, or
motion detector. They tend to cycle erratically. Things like a
furnace, electric heater, water pressure boost pump, pool heater,
demand water heater, sump pump, etc. There are also some uncommon
devices that cycle. Negative ion generator, parking lot light
controller, external HDD or NAS boxes, motion detector operated
devices, iPhone background sync, etc.

However, I've been fooled before with this pattern. I was looking for
such things, only to discover that the interference was coming from a
microwave oven at a local eatery. During lunch, the microwave ovens
were in use almost constantly. At other times, a minute or so at a
time. Kinda sounds like the original description.

Dumb story: Many years ago, I had a very difficult time trying to
find the source of short bursts of RFI. I tried for days and failed.
Oddly, the interference seemed wide spread and appeared almost
everywhere that I was sniffing. Eventually, the gears that drive my
brain engaged and I discovered that the Motorola Bravo pager that I
was carrying at the time, was the source. Argh.


Let's look at your list:
Think about something run by a thermostat, low control switch, or
motion detector. They tend to cycle erratically.


A thermostat - refrigerator, freezer, or heating / cooling tends to
cycle at a fairly constant rate, at least for the majority of the time
(an exception would be when a large amount of food is added to a
refrigerator, or a freezer, or when the set temerature of a thermostat
is changed). A motion detector would operate at erratic times, but
not for only 10 seconds.

Things like a
furnace, electric heater, water pressure boost pump, pool heater,
demand water heater, sump pump, etc.


Again, these would tend to operate on a regular cycle except for an
'on demand' water heater. However, the 'on demand' heater fails the
'on for one hour ' parameter.

There are also some uncommon
devices that cycle. Negative ion generator, parking lot light
controller, external HDD or NAS boxes, motion detector operated
devices, iPhone background sync, etc.

Again, these devices fail either the '10 second' or 'one hour'
parameter.

PlainBill
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On Sun, 08 Jan 2012 12:33:52 -0700, wrote:

Let's look at your list:


Think about something run by a thermostat, low control switch, or
motion detector. They tend to cycle erratically.


A thermostat - refrigerator, freezer, or heating / cooling tends to
cycle at a fairly constant rate, at least for the majority of the time
(an exception would be when a large amount of food is added to a
refrigerator, or a freezer, or when the set temerature of a thermostat
is changed).


I wasn't thinking of an appliance as much as an HVAC system that has a
time adjusted thermostat, and plenty of walk-in or walk-through
traffic. I've worked with a cold storage warehouse where the cooling
system would cycle as you describe as long as nothing was going in or
out. However, when large containers of vegetables went into the
warehouse, the cooler would run for about an hour before it started
cycling evenly as you suggest. Same with HVAC system in areas with
heavy foot traffic.

A motion detector would operate at erratic times, but
not for only 10 seconds.


That depends on what the motion detector is running. I'm thinking
more like a security DVR. When my cheap eBay piece of junk security
DVR detects motion, it starts recording continuously for about 5
minutes. If multiple cameras detect motion, with some overlap, it
could easily end up recording for hours.

There are motion detector lighting systems that work this way. For
example, a local eco-friendly business saves electricity by not having
the parking lights on unless it first detects motion. The lights are
timed to stay on for approximately twice the time it takes to walk
across the parking lot. I think that's about 4 minutes.

Things like a
furnace, electric heater, water pressure boost pump, pool heater,
demand water heater, sump pump, etc.


Again, these would tend to operate on a regular cycle except for an
'on demand' water heater. However, the 'on demand' heater fails the
'on for one hour ' parameter.


The on demand (tankless) water heater is very erratic. However, I
will admit that it doesn't run for very long after the water is shut
off. That's probably not it.

Electric heaters are much like the HVAC system. It really depends on
what's going on in the house or office. If there's heavy traffic, the
heater will cycle erratically. If it's a stable environment, it will
cycle evenly. If someone left a window open, it will cycle at the
whim of the wind.

Water pressure booster pumps are to get the water pressure up to about
30 psi minimum. They operate much like well pumps. If there's a
demand, they run. If there's no demand for water, they don't run.

Sump pumps might be a stretch, unless they're dealing with a water
leak that is also erratic. Add sewage pumps to the list for those
with toilets below the sewer or septic level.

There are also some uncommon
devices that cycle. Negative ion generator, parking lot light
controller, external HDD or NAS boxes, motion detector operated
devices, iPhone background sync, etc.

Again, these devices fail either the '10 second' or 'one hour'
parameter.


I beg to differ. One negative ion generator I had to deal with was
purchased on eBay and apparently had never bothered to pass FCC Part
15 radiation testing. It wiped the entire HF band. Oddly, it wasn't
the ozone err.... negative ion generator part that was generating the
RFI. It was the motor that pushed the air through a HEPA filter. The
motor would run whenever the device detected motion in the room as an
energy saving feature. I think the hysteresis was about 2 minutes,
but I'm not sure. If someone was in the room, it would easily run for
an hour.

I know a bit too much about external USB HDD drives and NAS boxes from
my day job. Usually, they just sit there doing nothing. However, if
the owner has it setup to do either continuous or scheduled backups,
it will run erratically according to the program parameters. The 10
second cycles could easily be some manner of continuous backup
program, such as Memeo, which comes with WD drives. Memeo sends a
copy of any file that changes on the computah to the external drive in
short bursts, when the machine isn't busy. That takes a few seconds.
The 1 hr run could be a more complete backup, or an image backup. Same
with the NAS storage box, except over the LAN instead of USB.

--
Jeff Liebermann

150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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On Sun, 08 Jan 2012 13:26:26 -0800, Jeff Liebermann
wrote:


There are motion detector lighting systems that work this way. For
example, a local eco-friendly business saves electricity by not having
the parking lights on unless it first detects motion. The lights are
timed to stay on for approximately twice the time it takes to walk
across the parking lot. I think that's about 4 minutes.


I have to say, this sounds like the opening scene from a murder
mystery. Only cars are big enough to start the lights. The woman
parks the car, away from the entrance so other cars won't ding hers.
She walks to the store, is almost there, remembers sometihing in the
car and has to go back, and on her second trip to the store, the
parking lot lights go off, and she hears footsteps behind her. We
only see her legs and his legs, and soon they are both running.

In the next scene, there are a lot of police standing around.


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On Sun, 08 Jan 2012 19:09:39 -0500, micky
wrote:

I have to say, this sounds like the opening scene from a murder
mystery. Only cars are big enough to start the lights.


Nope. They respond to people. I park there all the time. As I
vaguely recall, the motion sensors are located about half way up the
light poles. They take a few seconds to come on to full brightness,
and likewise, fade slowly when they turn off. Since the parking lot
lights are independently controlled, it's possible to have them come
on in sequence as one walks slowly across the lot.

The woman
parks the car, away from the entrance so other cars won't ding hers.
She walks to the store, is almost there, remembers sometihing in the
car and has to go back, and on her second trip to the store, the
parking lot lights go off, and she hears footsteps behind her. We
only see her legs and his legs, and soon they are both running.


Considering the time of day and the neighborhood, that's quite likely.
Fortunately, having the lights come on when the prospective car thief
enters the parking lot tends to provide a rather strong deterrent.

In the next scene, there are a lot of police standing around.


Possibly. The city police station is about 200 meters away.

The problem with finding sources of interference and such is the
hardware required. I used to do quite a bit of wi-fi sniffing,
searching for various sources of interference, leeches, hackers, DoS
sources, over-powered radios, and such. Same with searching for stuck
transmitters on commercial frequencies, foreign fishermen on US
frequencies, unlicensed operators, and premature LPFM stations. While
the equipment varies, it always seems to attract the attention of the
authorities. Walking through a busy shopping center parking lot, with
a fiberglass pole, topped with a small dish antenna, dragging a pile
of black boxes, with my face glued to a laptop. To the average
shopper, I was a cross between a terrorist and a visiting
intergalactic alien. No melodrama, but plenty of answering really
dumb questions. After a while, I learned to think first, and search
after. Have fun finding the interference source.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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On Sun, 08 Jan 2012 17:59:19 -0800, Jeff Liebermann
wrote:

On Sun, 08 Jan 2012 19:09:39 -0500, micky
wrote:

I have to say, this sounds like the opening scene from a murder
mystery. Only cars are big enough to start the lights.


Nope. They respond to people.


Dramatic license.

I park there all the time. As I
vaguely recall, the motion sensors are located about half way up the
light poles. They take a few seconds to come on to full brightness,
and likewise, fade slowly when they turn off. Since the parking lot
lights are independently controlled, it's possible to have them come
on in sequence as one walks slowly across the lot.

The woman
parks the car, away from the entrance so other cars won't ding hers.
She walks to the store, is almost there, remembers sometihing in the
car and has to go back, and on her second trip to the store, the
parking lot lights go off, and she hears footsteps behind her. We
only see her legs and his legs, and soon they are both running.


Considering the time of day and the neighborhood, that's quite likely.
Fortunately, having the lights come on when the prospective car thief
enters the parking lot tends to provide a rather strong deterrent.


If you want to sell this script, we're going to have to change some
things. If you won't cooperate, I'm not going to let you know when
the meeting is.

In the next scene, there are a lot of police standing around.


Possibly. The city police station is about 200 meters away.

The problem with finding sources of interference and such is the
hardware required. I used to do quite a bit of wi-fi sniffing,
searching for various sources of interference, leeches, hackers, DoS
sources, over-powered radios, and such. Same with searching for stuck
transmitters on commercial frequencies, foreign fishermen on US
frequencies, unlicensed operators, and premature LPFM stations. While
the equipment varies, it always seems to attract the attention of the
authorities. Walking through a busy shopping center parking lot, with
a fiberglass pole, topped with a small dish antenna, dragging a pile
of black boxes, with my face glued to a laptop. To the average
shopper, I was a cross between a terrorist and a visiting
intergalactic alien.


I'll bet!

No melodrama, but plenty of answering really
dumb questions. After a while, I learned to think first, and search
after. Have fun finding the interference source.


Thanks. I'll let you know how it goes. Though I've lost some
interest in finding the interfernce, and I'm turning my attention to
finishing the script and shopping it around.
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On Mon, 09 Jan 2012 00:01:58 -0500, micky
wrote:

Dramatic license.


I prefer poetic license:
http://www.LearnByDestroying.com/poetry/poetry.htm

If you're going to sell this script, it will need drama, suspense,
action, intrigue, politics, explosions, violence, a chase scene, sex,
and display the advertisers products. However, the one thing that
must never appear in the script is something that requires the viewer
to think. If there's even the slightest hint of "how does that
work?", the script won't sell. Science fiction and defective physics
are perfectly acceptable, as long as the actors all pretend that it's
real, and that nobody in the story questions the technology. To many
people, microprocessor controlled parking lot lights, triggered by
sophisticated PIR detectors, are more like magic than science.

I forgot to mention that the lights were all LED lights and VERY
bright. Something like this:
http://www.ledsmagazine.com/news/6/1/13
The real question is whether LED lights generate RF interference.
There's no consensus and plenty of opinions. My experience has been
that some do, and some don't. I have several consumer LED house
lights. Only one belches RFI. I haven't bothered to check which ones
are boost, buck, or both.
http://prudentrver.typepad.com/leds/2011/03/reasons-an-led-light-might-emit-radio-frequency-interference.html


--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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Posts: 412
Default Interference in FM radio reception.

On Jan 9, 2:50*am, Jeff Liebermann wrote:
On Mon, 09 Jan 2012 00:01:58 -0500, micky
wrote:

Dramatic license.


I prefer poetic license:
http://www.LearnByDestroying.com/poetry/poetry.htm

If you're going to sell this script, it will need drama, suspense,
action, intrigue, politics, explosions, violence, a chase scene, sex,
and display the advertisers products. *However, the one thing that
must never appear in the script is something that requires the viewer
to think. *If there's even the slightest hint of "how does that
work?", the script won't sell. *Science fiction and defective physics
are perfectly acceptable, as long as the actors all pretend that it's
real, and that nobody in the story questions the technology. *To many
people, microprocessor controlled parking lot lights, triggered by
sophisticated PIR detectors, are more like magic than science.

I forgot to mention that the lights were all LED lights and VERY
bright. *Something like this:
http://www.ledsmagazine.com/news/6/1/13
The real question is whether LED lights generate RF interference.
There's no consensus and plenty of opinions. *My experience has been
that some do, and some don't. *I have several consumer LED house
lights. *Only one belches RFI. *I haven't bothered to check which ones
are boost, buck, or both.
http://prudentrver.typepad.com/leds/2011/03/reasons-an-led-light-migh...

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558


I live in a small town in New Hampshire. About twenty years ago,
(before we got cable into town) I suddenly started to get numerous
calls from customers on one side of town complaining that TV channel 5
had just simply disappeared. My house was not affected and so this was
news to me. I visited one affected house and found a grey screen with
no audio. It appeared as though something was completely swamping the
entire channel. We contacted the FCC in Boston and what a waste of
time that was.
So I drove around town visiting different homes and asking if they
were also affected by this. Eventually I was able to draw a sort of
"lobe" of the pattern. The pattern was somewhat directional and the
radiating point appeared to be a communications tower set on private
property. The gentleman that owned the tower was very proud of it and
took me on a short tour of the facility. He would lease parts of this
tower to different commercial services. Among these services was a
radio data link to Massachusetts which operated on a frequency 200KHZ
below channel five's video carrier. While in the shack I noticed a
bandpass filter sitting on the shelf which was marked with his
operating frequency. I asked if that shouldn't have been in line with
the antenna and at that point the meeting became adversarial. I often
wondered if perhaps the filter was tuned incorrectly and it's
insertion into the line caused problems, so that was why he removed
it, or perhaps he was overmodulating, creating excessive sidebands
which poked into channel five. In any case I found it interesting
though that a few days after my visit the problem mysteriously
disappeared , never to return again.
When I was fifteen I built my first kit, an Eico CB radio. The
receiver was as wide as a barn door but it had an excellent
transmitter section. We lived in an apartment building in the Bronx
and most television sets of the day were built with 21MHZ IF strips.
So when I keyed that transmitter no one for blocks around was able to
watch channel two on their TV sets. I installed a low pass fiIter on
my rig and I lost track of how many high pass filters I installed for
my neighbors.
I would also think about your radio's IF frequency, although on second
thought that would not be limited to only certain channels.
I'd really like to know if you find this thing. Please keep us
informed. Lenny
  #25   Report Post  
Posted to sci.electronics.repair
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Posts: 4,045
Default Interference in FM radio reception.

On Wed, 11 Jan 2012 08:07:47 -0800 (PST), klem kedidelhopper
wrote:

I live in a small town in New Hampshire. About twenty years ago,
(before we got cable into town) I suddenly started to get numerous
calls from customers on one side of town complaining that TV channel 5
had just simply disappeared.


Many such TV's had AFC (automagic frequency control). Give it a
strong nearby carrier, and it will lock on the carrier instead of the
TV signal carrier.

So I drove around town visiting different homes and asking if they
were also affected by this. Eventually I was able to draw a sort of
"lobe" of the pattern.


Nicely done. That sounds like quite a bit of work.

Among these services was a
radio data link to Massachusetts which operated on a frequency 200KHZ
below channel five's video carrier.


It had to be more than 200Khz. Channel 5 video is at 77.25MHz. The
75MHz "telemetry and radio control" band is roughly from 75 to 76MHz.
It would need to be more like 2MHz below the CH5 carrier. Still, for
a 6MHz wide TV signal, that's quite close if running high power.
However, as I recall (and am too lazy to lookup), the highest power
allowed at 75MHz is something like 1 watt. I don't think it was a
filter, but rather far too much power.

While in the shack I noticed a
bandpass filter sitting on the shelf which was marked with his
operating frequency. I asked if that shouldn't have been in line with
the antenna and at that point the meeting became adversarial.


Nice detective work. I once gave a visiting FCC inspector an
"unofficial" tour of our mountain top radio site. I explained
everything and answered many questions. In gratitude, he sent about
100 "failure to post licenses" and other administrivia violations, not
to the service company, but directly to the customers. That didn't
cost much in fines, but as a result, we lost a few customers. I don't
give tours any more.

I often
wondered if perhaps the filter was tuned incorrectly and it's
insertion into the line caused problems, so that was why he removed
it, or perhaps he was overmodulating, creating excessive sidebands
which poked into channel five.


My guess is that he was running too much power trying to span the
distance between NH and Boston. Adding the filter probably increased
the loss to the point where the link failed. My guess is that it was
taken off the air when the site owner discovered what was happening.

When I was fifteen I built my first kit, an Eico CB radio. The
receiver was as wide as a barn door but it had an excellent
transmitter section. We lived in an apartment building in the Bronx
and most television sets of the day were built with 21MHZ IF strips.
So when I keyed that transmitter no one for blocks around was able to
watch channel two on their TV sets. I installed a low pass fiIter on
my rig and I lost track of how many high pass filters I installed for
my neighbors.


Ummm... you have it somewhat wrong. The hi pass filter goes on the 27
MHz xmitter, in order to remove any spurious rubbish from the transmit
signal at 21.4MHz. A low pass filter would NOT work on the TV set as
the frequency range is 54 to 800MHz and a low pass filter would block
all of it. However, a 21MHz notch filter on the antenna would work
wonders.

Incidentally, I helped an older friend build the same EICO CB radio.
The tunable receiver was horrible, but at the time, I didn't know
quality when I saw it.
http://www.radiomuseum.org/r/eico_770770.html

I would also think about your radio's IF frequency, although on second
thought that would not be limited to only certain channels.
I'd really like to know if you find this thing. Please keep us
informed. Lenny


Unless the front end is broadband and crude, the IF rejection of
modern receivers is quite good.

For 2.4GHz, the last device that used an IF frequency was the ancient
Lucent chipset and possible the early IBM wireless oddities. Literally
everything for the last 10 years or so has been direct conversion,
with no IF frequency. Google for "802.11 direct conversion receiver"
for hundreds of examples. IF feedthrough is unlikely if there's no
IF.
--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558


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Posts: 4,045
Default Interference in FM radio reception.

On Wed, 11 Jan 2012 09:18:11 -0800, Jeff Liebermann
wrote:

Ummm... you have it somewhat wrong. The hi pass filter goes on the 27
MHz xmitter, in order to remove any spurious rubbish from the transmit
signal at 21.4MHz. A low pass filter would NOT work on the TV set as
the frequency range is 54 to 800MHz and a low pass filter would block
all of it. However, a 21MHz notch filter on the antenna would work
wonders.


Argh. That's all wrong. I somehow merged the 21.4IF feedthru problem
with the CB harmonic filter. The lo-pass filter should be on the CB
xmitter, to reduce the 2nd harmonic that trashed Channel 2. The 54MHz
high pass filter goes on TV, to keep the CB radio from generating
harmonics in the tuner section.

Remind me not to post anything before my morning coffee fix.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
  #27   Report Post  
Posted to sci.electronics.repair
external usenet poster
 
Posts: 412
Default Interference in FM radio reception.

On Jan 11, 12:18*pm, Jeff Liebermann wrote:
On Wed, 11 Jan 2012 08:07:47 -0800 (PST), klem kedidelhopper

wrote:
I live in a small town in New Hampshire. About twenty years ago,
(before we got cable into town) I suddenly started to get numerous
calls from customers on one side of town complaining that TV channel 5
had just simply disappeared.


Many such TV's had AFC (automagic frequency control). *Give it a
strong nearby carrier, and it will lock on the carrier instead of the
TV signal carrier.

So I drove around town visiting different homes and asking if they
were also affected by this. Eventually I was able to draw a sort of
"lobe" of the pattern.


Nicely done. *That sounds like quite a bit of work.

Among these services was a
radio data link to Massachusetts which operated on a frequency 200KHZ
below channel five's video carrier.


It had to be more than 200Khz. *Channel 5 video is at 77.25MHz. *The
75MHz "telemetry and radio control" band is roughly from 75 to 76MHz.
It would need to be more like 2MHz below the CH5 carrier. *Still, for
a 6MHz wide TV signal, that's quite close if running high power.
However, as I recall (and am too lazy to lookup), the highest power
allowed at 75MHz is something like 1 watt. *I don't think it was a
filter, but rather far too much power.

While in the shack I noticed a
bandpass filter sitting on the shelf which was marked with his
operating frequency. I asked if that shouldn't have been in line with
the antenna and at that point the meeting became adversarial.


Nice detective work. *I once gave a visiting FCC inspector an
"unofficial" tour of our mountain top radio site. *I explained
everything and answered many questions. *In gratitude, he sent about
100 "failure to post licenses" and other administrivia violations, not
to the service company, but directly to the customers. *That didn't
cost much in fines, but as a result, we lost a few customers. *I don't
give tours any more.

I often
wondered if perhaps the filter was tuned incorrectly and it's
insertion into the line caused problems, so that was why he removed
it, or perhaps he was overmodulating, creating excessive sidebands
which poked into channel five.


My guess is that he was running too much power trying to span the
distance between NH and Boston. *Adding the filter probably increased
the loss to the point where the link failed. *My guess is that it was
taken off the air when the site owner discovered what was happening.

When I was fifteen I *built my first kit, an Eico CB radio. The
receiver was as wide as a barn door but it had an excellent
transmitter section. We lived in an apartment building in the Bronx
and most television sets of the day were built with 21MHZ IF strips.
So when I keyed that transmitter no one for blocks around was able to
watch channel two on their TV sets. I installed a low pass fiIter on
my rig and I lost track of how many high pass filters I installed for
my neighbors.


Ummm... you have it somewhat wrong. *The hi pass filter goes on the 27
MHz xmitter, in order to remove any spurious rubbish from the transmit
signal at 21.4MHz. *A low pass filter would NOT work on the TV set as
the frequency range is 54 to 800MHz and a low pass filter would block
all of it. *However, a 21MHz notch filter on the antenna would work
wonders.

Incidentally, I helped an older friend build the same EICO CB radio.
The tunable receiver was horrible, but at the time, I didn't know
quality when I saw it.
http://www.radiomuseum.org/r/eico_770770.html

I would also think about your radio's IF frequency, although on second
thought that would not be limited to only certain channels.
I'd really like to know if you find this thing. Please keep us
informed. Lenny


Unless the front end is broadband and crude, the IF rejection of
modern receivers is quite good.

For 2.4GHz, the last device that used an IF frequency was the ancient
Lucent chipset and possible the early IBM wireless oddities. Literally
everything for the last 10 years or so has been direct conversion,
with no IF frequency. *Google for "802.11 direct conversion receiver"
for hundreds of examples. *IF feedthrough is unlikely if there's no
IF.
--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558


Thanks for your comments Jeff. You're correct about the filters. I had
them reversed. And the Radio museum page is close. I think the 770
was four or five channels of crystal control transmit. My rig was
the 760 and I built two of them. Initially it had only one crystal for
transmit. I had to cut a small window out of the back near the crystal
socket so that I could change crystals. It was a pain and truly kind
of short sighted on Eico's part. They also offered (I think the model
was a 775) with a vibrator power supply. I eventually installed 23
crystals and a switch in a box underneath the radio to accommodate all
channels. I also bought the special transformer, vibrator and other
necessary components to convert my rig for mobile use. Ultimately the
vibrator proved to be much too noisy and I replaced it with a blocking
oscillator circuit built around a 400HZ power transformer. Probably
wasn't very efficient but It It worked well, it was QUIET and it just
happened to put out the 275V B+ that the radio required. I have great
memories of bombing around The Bronx in 1966 with my CB and 102 inch
whip antenna in my 1953 Desoto. Incidentally I went on to work for
Eico as a QC technician a few years later for a short period too.
Lenny
  #28   Report Post  
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Posts: 412
Default Interference in FM radio reception.

On Jan 11, 12:18*pm, Jeff Liebermann wrote:
On Wed, 11 Jan 2012 08:07:47 -0800 (PST), klem kedidelhopper

wrote:
I live in a small town in New Hampshire. About twenty years ago,
(before we got cable into town) I suddenly started to get numerous
calls from customers on one side of town complaining that TV channel 5
had just simply disappeared.


Many such TV's had AFC (automagic frequency control). *Give it a
strong nearby carrier, and it will lock on the carrier instead of the
TV signal carrier.

So I drove around town visiting different homes and asking if they
were also affected by this. Eventually I was able to draw a sort of
"lobe" of the pattern.


Nicely done. *That sounds like quite a bit of work.

Among these services was a
radio data link to Massachusetts which operated on a frequency 200KHZ
below channel five's video carrier.


It had to be more than 200Khz. *Channel 5 video is at 77.25MHz. *The
75MHz "telemetry and radio control" band is roughly from 75 to 76MHz.
It would need to be more like 2MHz below the CH5 carrier. *Still, for
a 6MHz wide TV signal, that's quite close if running high power.
However, as I recall (and am too lazy to lookup), the highest power
allowed at 75MHz is something like 1 watt. *I don't think it was a
filter, but rather far too much power.

While in the shack I noticed a
bandpass filter sitting on the shelf which was marked with his
operating frequency. I asked if that shouldn't have been in line with
the antenna and at that point the meeting became adversarial.


Nice detective work. *I once gave a visiting FCC inspector an
"unofficial" tour of our mountain top radio site. *I explained
everything and answered many questions. *In gratitude, he sent about
100 "failure to post licenses" and other administrivia violations, not
to the service company, but directly to the customers. *That didn't
cost much in fines, but as a result, we lost a few customers. *I don't
give tours any more.

I often
wondered if perhaps the filter was tuned incorrectly and it's
insertion into the line caused problems, so that was why he removed
it, or perhaps he was overmodulating, creating excessive sidebands
which poked into channel five.


My guess is that he was running too much power trying to span the
distance between NH and Boston. *Adding the filter probably increased
the loss to the point where the link failed. *My guess is that it was
taken off the air when the site owner discovered what was happening.

When I was fifteen I *built my first kit, an Eico CB radio. The
receiver was as wide as a barn door but it had an excellent
transmitter section. We lived in an apartment building in the Bronx
and most television sets of the day were built with 21MHZ IF strips.
So when I keyed that transmitter no one for blocks around was able to
watch channel two on their TV sets. I installed a low pass fiIter on
my rig and I lost track of how many high pass filters I installed for
my neighbors.


Ummm... you have it somewhat wrong. *The hi pass filter goes on the 27
MHz xmitter, in order to remove any spurious rubbish from the transmit
signal at 21.4MHz. *A low pass filter would NOT work on the TV set as
the frequency range is 54 to 800MHz and a low pass filter would block
all of it. *However, a 21MHz notch filter on the antenna would work
wonders.

Incidentally, I helped an older friend build the same EICO CB radio.
The tunable receiver was horrible, but at the time, I didn't know
quality when I saw it.
http://www.radiomuseum.org/r/eico_770770.html

I would also think about your radio's IF frequency, although on second
thought that would not be limited to only certain channels.
I'd really like to know if you find this thing. Please keep us
informed. Lenny


Unless the front end is broadband and crude, the IF rejection of
modern receivers is quite good.

For 2.4GHz, the last device that used an IF frequency was the ancient
Lucent chipset and possible the early IBM wireless oddities. Literally
everything for the last 10 years or so has been direct conversion,
with no IF frequency. *Google for "802.11 direct conversion receiver"
for hundreds of examples. *IF feedthrough is unlikely if there's no
IF.
--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558


Thanks for your comments Jeff. You're correct about the filters. I had
them reversed. And the Radio museum page is close. I think the 770
was four or five channels of crystal control transmit. My rig was
the 760 and I built two of them. Initially it had only one crystal for
transmit. I had to cut a small window out of the back near the crystal
socket so that I could change crystals. It was a pain and truly kind
of short sighted on Eico's part. They also offered (I think the model
was a 775) with a vibrator power supply. I eventually installed 23
crystals and a switch in a box underneath the radio to accommodate all
channels. I also bought the special transformer, vibrator and other
necessary components to convert my rig for mobile use. Ultimately the
vibrator proved to be much too noisy and I replaced it with a blocking
oscillator circuit built around a 400HZ power transformer. Probably
wasn't very efficient but It It worked well, it was QUIET and it just
happened to put out the 275V B+ that the radio required. I have great
memories of bombing around The Bronx in 1966 with my CB and 102 inch
whip antenna in my 1953 Desoto. Incidentally I went on to work for
Eico as a QC technician a few years later for a short period too.
Lenny
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Posts: 454
Default Interference in FM radio reception.

On Wed, 11 Jan 2012 10:27:50 -0800, Jeff Liebermann
wrote:

On Wed, 11 Jan 2012 09:18:11 -0800, Jeff Liebermann
wrote:

Ummm... you have it somewhat wrong. The hi pass filter goes on the 27
MHz xmitter, in order to remove any spurious rubbish from the transmit
signal at 21.4MHz. A low pass filter would NOT work on the TV set as
the frequency range is 54 to 800MHz and a low pass filter would block
all of it. However, a 21MHz notch filter on the antenna would work
wonders.


Argh. That's all wrong. I somehow merged the 21.4IF feedthru problem
with the CB harmonic filter. The lo-pass filter should be on the CB
xmitter, to reduce the 2nd harmonic that trashed Channel 2. The 54MHz
high pass filter goes on TV, to keep the CB radio from generating
harmonics in the tuner section.

Remind me not to post anything before my morning coffee fix.


Y0u had me worried there.

?-)
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Posted to sci.electronics.repair
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Posts: 412
Default Interference in FM radio reception.

On Jan 13, 9:20*pm, josephkk wrote:
On Wed, 11 Jan 2012 10:27:50 -0800, Jeff Liebermann
wrote:



On Wed, 11 Jan 2012 09:18:11 -0800, Jeff Liebermann
wrote:


Ummm... you have it somewhat wrong. *The hi pass filter goes on the 27
MHz xmitter, in order to remove any spurious rubbish from the transmit
signal at 21.4MHz. *A low pass filter would NOT work on the TV set as
the frequency range is 54 to 800MHz and a low pass filter would block
all of it. *However, a 21MHz notch filter on the antenna would work
wonders.


Argh. *That's all wrong. *I somehow merged the 21.4IF feedthru problem
with the CB harmonic filter. *The lo-pass filter should be on the CB
xmitter, to reduce the 2nd harmonic that trashed Channel 2. *The 54MHz
high pass filter goes on TV, to keep the CB radio from generating
harmonics in the tuner section.


Remind me not to post anything before my morning coffee fix.


Y0u had me worried there.

?-)

Sometimes I worry myself. I thought they were right the first time but
I guess I am a bit foggy sometimes. Save some coffee for me too, OK?
Lenny


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Default Interference in FM radio reception.

On Fri, 13 Jan 2012 18:20:40 -0800, josephkk
wrote:

Remind me not to post anything before my morning coffee fix.


Y0u had me worried there.
?-)


The effect is psychological. One sip of coffee has the same effect as
drinking the whole cup. Whatever the mechanism, I find it difficult
to think clearly before my morning fix. Never mind that I'm also
reading email, replying to email, talking on the phone, planning my
day, dealing with paperwork, yacking on the ham radio, cleaning house,
reading a magazine, watching TV, and assembling lunch at the same
time. Simultaneously doing 10 things badly, takes less time than
sequentially doing each correctly.

To error is human, and I sometimes need to reassure myself that I'm
still human.

--
Jeff Liebermann
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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