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Default OTA TV reception problems

I tried posting something about this in the past but got no response. I'm holing that this time someone might read it who may have a theory as to what could be going on.

I live in southern New Hampshire and watch OTA TV out of Boston, which is about 60 miles from here. Lately I as well as several other people I know have been experiencing intermittent problems with channel four. While most other channels are presently operating fine, for the past 10 days or so channel 4's signal has been in the toilet. This station, WBZ TV operates on UHF channel 30, runs 825KW, and has an antenna height of 390 meters. By contrast Channel 5, WCVB, operates on UHF channel 20, runs 625 KW, and shares the same tower and has it's antenna at the same height as channel 4's, and we never have any problems with that channel. Could propagation be that much different 60 MHZ apart? What is really weird is that the signal just drops to almost nothing.

I discussed this with the chief engineer at Channel four and he had no explanation for this. Does anyone have any theories about this? Thanks, Lenny
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On 11/6/2016 4:40 PM, wrote:
I tried posting something about this in the past but got no response. I'm holing that this time someone might read it who may have a theory as to what could be going on.

I live in southern New Hampshire and watch OTA TV out of Boston, which is about 60 miles from here. Lately I as well as several other people I know have been experiencing intermittent problems with channel four. While most other channels are presently operating fine, for the past 10 days or so channel 4's signal has been in the toilet. This station, WBZ TV operates on UHF channel 30, runs 825KW, and has an antenna height of 390 meters. By contrast Channel 5, WCVB, operates on UHF channel 20, runs 625 KW, and shares the same tower and has it's antenna at the same height as channel 4's, and we never have any problems with that channel. Could propagation be that much different 60 MHZ apart? What is really weird is that the signal just drops to almost nothing.

I discussed this with the chief engineer at Channel four and he had no explanation for this. Does anyone have any theories about this? Thanks, Lenny

There's signal strength, signal quality/modulation, interference and
tuner quality.

Having two stations on the same tower reduces the number of variables.

I'm only about 10 miles from the tower, but there are hills all around.
Signal strength is high, but there are a lot of reflections.
I did many experiments varying the antenna direction and changing signal
strength into the tuners. Best picture stability was not always consistent
with best signal strength. When trying to use one tuner and one antenna
for multiple stations, I found that I had to attenuate the signal to get
a picture on some stations.

My neighbor has a metal pole building. I found moving the antenna
to the other end of the house made a dramatic improvement. Doesn't take
much a reflection that might be from far away to wreak havoc on your
signal due to multipath. Did Trump put up a new tower in your vicinity?

Currently, I have a win7 computer with 4 tuners. A single antenna and
distribution amplifier with an output for each tuner. Over the years,
I've upgraded the tuners so I no longer have to vary the signal
strength to fit a particular tuner. I find that some tuners
don't like specific channels. Luckily, media center will let me blacklist
tuners on various channels.

Interference can come from unexpected sources. Your neighbor's wifi
might be mixing in a corroded gutter junction with some other radio
signal. The result trashes the signal quality of your TV station.

I once had a towing company radio mix with my radio repeater output
that landed exactly at the IF frequency of my other radio.

If you have access to a spectrum analyzer, you can hook it to your
antenna and look at the relative signal strengths.
Look at the modulation for each channel. I found that signals were
good when the "bart's head" display was flat on top. Didn't take much
noise or tilt to render the channel unwatchable, even on very strong
signals.

ATSC is not very forgiving.
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Default OTA TV reception problems

On Sun, 6 Nov 2016 16:40:35 -0800 (PST),
wrote:

I live in southern New Hampshire and watch OTA TV out of Boston,
which is about 60 miles from here. Lately I as well as several
other people I know have been experiencing intermittent problems
with channel four. While most other channels are presently
operating fine, for the past 10 days or so channel 4's signal
has been in the toilet.


The signal varies in strength and quality, you could be dealing with
knife edge diffraction off of towers, hills, and buildings along the
line of sight. At 60 miles, you're almost certain to have a potential
problem with Fresnel zone diffraction.
http://www.proxim.com/products/knowledge-center/calculations/calculations-fresnel-clearance-zone
I can generate a path profile to see if there are any obvious
problems, but I need to know the lat-long of your location and
elevation of your antenna. Here's a sample output:
http://802.11junk.com/jeffl/coverage/RST/

This station, WBZ TV operates on UHF channel 30, runs 825KW,
and has an antenna height of 390 meters. By contrast Channel 5,
WCVB, operates on UHF channel 20, runs 625 KW, and shares the
same tower and has it's antenna at the same height as channel 4's,
and we never have any problems with that channel.


https://transition.fcc.gov/fcc-bin/tvq?call=WBZ
https://transition.fcc.gov/fcc-bin/tvq?call=WCVB
The antennas appear to be almost identical. I just checked the FCC
41dBu service contours for both stations and they are identical.
http://802.11junk.com/jeffl/coverage/KBCZ-WBZ/KVCB-WBZ.jpg
Transmit power difference isn't going to do much. By all reason and
logic, the signal strengths should be identical assuming the path is
clear of obstructions. Note that the 41dBu contours do NOT represent
the actual coverage pattern of the stations. The FCC calculations are
based on the assumption that the earth is flat and lacks mountains and
hills. These coverage maps should be better:
http://www.tvfool.com/index.php?option=com_content&task=view&id=15&Itemi d=1

You might try checking what might be expected at your location in the
way of TV reception:
http://www.tvfool.com
Check the calculated signal strengths and see if it's even
theoretically possible to receive either station at your unspecified
location.

Could propagation be that much different 60 MHZ apart? What
is really weird is that the signal just drops to almost nothing.


Yes, due to frequency selective fading. What happens is that you may
have two paths between the TV station and your receiving antenna. If
the reflected path is some odd numbered multiple of 1/2 wavelength,
the signals will cancel. At about 500 MHz, 1/2 wavelength is about
1ft. Move your antenna 1ft in any direction and see if it makes any
difference.

I discussed this with the chief engineer at Channel four and
he had no explanation for this. Does anyone have any theories
about this? Thanks, Lenny


Oh, lots of theories. For example, a broken TV tuner that has a
problem on some channels. Some kind of OTA TV amplifier with an
uneven frequency response. Badly terminated or connected TV coax
cable causing a notch at one frequency. TV antenna with a broken
element causing a notch at one frequency. Local source of
interference on one TV channel, but not the other. It might be that
one TV station is having transmitter or antenna problems. I could
probably conjure a few others.

The easiest way to troubleshoot this is by substitution. Start with a
different antenna connected directly to the TV with a different
coaxial cable. It will probably not be as good as a rooftop antenna,
but it should hear something. Compare the signal levels of the two
stations. If they're the same, you're problem is somewhere in the
antenna, amp, or coax feed system. If they're still different, it
might be the TV. Try a different TV.

Good luck.
--
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 OTA TV reception problems

In article ,
wrote:

I tried posting something about this in the past but got no response. I'm
holing that this time someone might read it who may have a theory as to what
could be going on.

I live in southern New Hampshire and watch OTA TV out of Boston, which is
about 60 miles from here. Lately I as well as several other people I know
have been experiencing intermittent problems with channel four. While most
other channels are presently operating fine, for the past 10 days or so
channel 4's signal has been in the toilet. This station, WBZ TV operates on
UHF channel 30, runs 825KW, and has an antenna height of 390 meters. By
contrast Channel 5, WCVB, operates on UHF channel 20, runs 625 KW, and shares
the same tower and has it's antenna at the same height as channel 4's, and we
never have any problems with that channel. Could propagation be that much
different 60 MHZ apart? What is really weird is that the signal just drops to
almost nothing.

I discussed this with the chief engineer at Channel four and he had no
explanation for this. Does anyone have any theories about this? Thanks, Lenny


Lenny-

If you provide data to Jeff, he can give you a more accurate prediction
of how well you should receive the station.

As a rough estimate, the range of an signal in miles is the square root
of twice the sum of transmitting and receiving antenna heights in feet.
For 60 miles, the sum of heights would be 1800 Feet.

As others mentioned, reflections can make a difference. Was a large
building erected about the time you noticed the reduction in signal?

Fred
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Default OTA TV reception problems

On Sunday, November 6, 2016 at 7:40:38 PM UTC-5, wrote:
I tried posting something about this in the past but got no response. I'm holing that this time someone might read it who may have a theory as to what could be going on.

I live in southern New Hampshire and watch OTA TV out of Boston, which is about 60 miles from here. Lately I as well as several other people I know have been experiencing intermittent problems with channel four. While most other channels are presently operating fine, for the past 10 days or so channel 4's signal has been in the toilet. This station, WBZ TV operates on UHF channel 30, runs 825KW, and has an antenna height of 390 meters. By contrast Channel 5, WCVB, operates on UHF channel 20, runs 625 KW, and shares the same tower and has it's antenna at the same height as channel 4's, and we never have any problems with that channel. Could propagation be that much different 60 MHZ apart? What is really weird is that the signal just drops to almost nothing.

I discussed this with the chief engineer at Channel four and he had no explanation for this. Does anyone have any theories about this? Thanks, Lenny



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Default OTA TV reception problems

I live in southern New Hampshire and watch OTA TV out of Boston, which is about 60 miles from here.
Lately I as well as several other people I know have been experiencing intermittent problems with
channel four. While most other channels are presently operating fine, for the past 10 days or so
channel 4's signal has been in the toilet. This station, WBZ TV operates on UHF channel 30, runs
825KW, and has an antenna height of 390 meters. By contrast Channel 5, WCVB, operates on UHF channel
20, runs 625 KW, and shares the same tower and has it's antenna at the same height as channel 4's, and
we never have any problems with that channel. Could propagation be that much different 60 MHZ apart?
What is really weird is that the signal just drops to almost nothing.

I discussed this with the chief engineer at Channel four and he had no explanation for this. Does
anyone have any theories about this? Thanks, Lenny


That sounds as if you may have a multipath situation. The signal from
the transmitters is reaching your receive antenna via two different
paths - e.g. once directly, and once after reflection off of a
building or mountain or ???.

If the two different paths deliver signals that happen to be of nearly
equal strength, and nearly 180 degrees out of phase with one another,
they will largely cancel out when they are combined by your antenna,
and the signal strength will take a huge dive.

Because the effective length of the signal paths (measured in
wavelengths) is a function of the frequency, it's entirely possible
for two different channels transmitted from the same tower to behave
very differently. Even a small frequency difference can shift the
difference-in-path-length by 180 degrees. 60 MHz difference is far
more than enough for this effect to show up.

Other possibilities:

- Somebody may have put up some sort of structure which happens to
resonate at the UHF Channel 30 frequency, thus creating a
frequency-selective reflector.

- It's possible that another station is now operating on Channel 30,
somewhere within antenna range of you, and its signal is now
interfering with WBZ. This might indicate that a new station has
gone on-line (or an existing one has changed frequencies) or might
indicate that there's some tropospheric ducting or other form of
"skip" bringing an out-of-area station's signal to you.

- There might be some form of local interference - a spurious
transmission on or near the Channel 30 frequency.

https://www.fcc.gov/media/television/tv-query can be used to find
stations on specific frequencies. You could plug in your location and
get a list of all stations (or those on channel 30) within a specific
radius of your location.




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On Mon, 07 Nov 2016 09:09:26 -0800, Jeff Liebermann
wrote:

https://transition.fcc.gov/fcc-bin/tvq?call=WBZ
https://transition.fcc.gov/fcc-bin/tvq?call=WCVB


Coverage maps of WBZ and WCVB. Please note that WBZ has or had a
transmit power upgrade application pending with the FCC to increase
their output to 941kW. I'm not sure if the coverage map is for 825kW
or 941kW.
http://802.11junk.com/jeffl/coverage/KBCZ-WBZ/WBZ-coverage.jpg
http://802.11junk.com/jeffl/coverage/KBCZ-WBZ/WCVB-coverage.jpg
Both coverage maps look fairly close. However, at 60 miles you're
well outside the "normal" coverage area. I'm wondering why WCVB works
at 60 miles. What do you have for an antenna and amp at your end?

I'm otto time for this today. More tomorrow.

--
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 OTA TV reception problems

wrote:

I tried posting something about this in the past but got no response. I'm
holing that this time someone might read it who may have a theory as to
what could be going on.

I live in southern New Hampshire and watch OTA TV out of Boston, which is
about 60 miles from here. Lately I as well as several other people I know
have been experiencing intermittent problems with channel four. While most
other channels are presently operating fine, for the past 10 days or so
channel 4's signal has been in the toilet. This station, WBZ TV operates
on UHF channel 30, runs 825KW, and has an antenna height of 390 meters. By
contrast Channel 5, WCVB, operates on UHF channel 20, runs 625 KW, and
shares the same tower and has it's antenna at the same height as channel
4's, and we never have any problems with that channel. Could propagation
be that much different 60 MHZ apart? What is really weird is that the
signal just drops to almost nothing.

I discussed this with the chief engineer at Channel four and he had no
explanation for this. Does anyone have any theories about this? Thanks,
Lenny

Anybody hit or knock down a pole in the area? I assume your neighborhood is
wired for cable. Damage to poles can knock connectors partially loose,
allowing a LOT of signal to flow onto the outer sheath. Could be a signal
right on the same frequency as Chan 4. I remember a LONG time ago, we had a
lightning storm, and someone in the area reported TV interference (back in
the analog days, you could easily tell it was interference) . Turned out
the lightning had blown out the output filters on a two-way radio base
station, so it was radiating at the drive frequency. Could be something
similar, a radio transmitter emitting unwanted frequencies. I've even heard
of rusty fences and the like developing rectifiying junctions that were
mixing various broadcast frequencies and blotting out one particular
channel.

Are the others with the same problem very close to you, or some distance
away? If very close, then likely it is a very local interference source,
might be VERY weak, and darned hard to find. If they are miles away, then
it is a larger source, and maybe something the station might be willing to
send a guy out with a field intensity meter to see if he can find where it
is coming from.

Hmmm, anybody put up a big building nearby? Some of these glass towers can
become excellent near-microwave reflectors, and might be bouncing signals
from some other area toward your location.

Could also be a wireless security system, baby monitor, wireless cameras, or
some other gear of that sort that is out of adjustment.


Jon
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Default OTA TV reception problems

On Sunday, November 6, 2016 at 4:40:38 PM UTC-8, wrote:

... for the past 10 days or so channel 4's signal has been in the toilet. This station, WBZ TV operates on UHF channel 30, runs 825KW, and has an antenna height of 390 meters. By contrast Channel 5, WCVB, operates on UHF channel 20, runs 625 KW, and shares the same tower and has it's antenna at the same height as channel 4's, and we never have any problems with that channel. Could propagation be that much different 60 MHZ apart? What is really weird is that the signal just drops to almost nothing.


If there's a nearby signal to "channel 30", it could be saturating your input amplifier. It's
counterintuitive, but try a passive attenuator and see if it improves your reception. The
attenuator has to be between the antenna and the FIRST amplifier for the RF signal,
so if you have a mast-mounted preamp, that's a problem.

Saturation can happen in an RF input amplifier, reducing the signal gain, due to an off-frequency
signal that is completely filtered out in later stages. I'm not sure if your signal indication
would read the spurious signal or not.

If this is a longterm problem, the best solution is an RF trap tuned for the too-strong signal.
That won't hurt your signal strength for the other channel, like an attenuator does.

http://www.mcmelectronics.com/browse/Attenuators/0000000801
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Default OTA TV reception problems

On Sunday, November 6, 2016 at 7:40:38 PM UTC-5, wrote:
I tried posting something about this in the past but got no response. I'm holing that this time someone might read it who may have a theory as to what could be going on.

I live in southern New Hampshire and watch OTA TV out of Boston, which is about 60 miles from here. Lately I as well as several other people I know have been experiencing intermittent problems with channel four. While most other channels are presently operating fine, for the past 10 days or so channel 4's signal has been in the toilet. This station, WBZ TV operates on UHF channel 30, runs 825KW, and has an antenna height of 390 meters. By contrast Channel 5, WCVB, operates on UHF channel 20, runs 625 KW, and shares the same tower and has it's antenna at the same height as channel 4's, and we never have any problems with that channel. Could propagation be that much different 60 MHZ apart? What is really weird is that the signal just drops to almost nothing.

I discussed this with the chief engineer at Channel four and he had no explanation for this. Does anyone have any theories about this? Thanks, Lenny


Here is some background information from my previous posting: (I was thinking "drive" miles when I said that we were 60 miles from Boston). As the crow flies we are about 45. Sorry for that bit of misinformation. The following previous post was when the problem first surfaced.


Sep 21
For the past ten days or so we have been having problems with TV channel 4. This station broadcasts on UHF from Boston Mass. and we are about 45 miles (as the crow flies) from the transmitter. The antenna is an old, but in good condition, very high gain Channel Master 5 foot parabolic which is mounted on a tripod about 6 feet off the roof. There is a mast mounted Winegard GA 8780 preamplifier with a 28 DB UHF section along with a very low noise figure mounted about 2 feet from the antenna. The cable is RG6 Quad which goes into a two way splitter. We have several different receivers, Converter boxes) but the one I use for assessment because it shows signal quality as well as signal strength is a Channel Master 7001. Our elevation is 410 feet and we are surrounded by trees, some deciduous and some pine.

Most of the time, in spite of this not so ideal situation, (location) I can receive the three networks and a few independents. The signal display on the converter shows, as two horizontal bars, "signal quality" and "signal level". On most channels most of the time signal quality is pegged at 100 percent and signal level runs between 45 and 55 percent. Within this window I usually have no problems with reception. As long as signal quality doesn't fold back I usually will get no drop outs. If it should falter excessively though both picture and sound will break up and intermittently freeze. So I'm pretty familiar with what conditions will produce a good signal.

Lately Channel 4 although displaying 54 percent signal level and 100 percent signal quality has had very slight "tearing streaks" going through the picture. If these aberrations only affected the picture we would be able to watch the program. However this problem seems to chop up the sound as well. This makes it impossible to watch a program.

The weather of late has been hot and humid, which is atypical for New England this time of year. I've noticed in the past that during this type of weather we do sometimes lose reception on several channels for a day or two but never this long. I'm just wondering if anyone might have a theory as to what could be happening here. This only seems to affect channel 4, (where all our shows happen to be). Thanks, Lenny

I also corresponded with the chief engineer at WBZ and got this back.

Lenny,



My apologies for the delay in replying.



I dont have a good answer for why your reception has degraded recently. We have not been having any trouble with our transmission systems.



Your installation sounds like a good one, though I think it may be a bit overdone, as a high-gain antenna in combination with 28 dB of amplification is probably more than you need, even at that distance. For comparison, I live 43.1 air miles from the transmit antenna, and I use a Channel Master 4228 8-bay bowtie antenna on the roof of my one-story house, with no amplification. I get full-bore signal into the TV on almost all channels. We have had incidences with viewers who had too much amplification in which they lost WBZ and WFXT, which had the most powerful signals in the Boston market (at the time). They were overdriving their TVs and as a result suffering the loss of the two stations they should have received with the least effort.



Wish I had a more definitive answer€¦





Robert Yankowitz, CPBE

WBZ-TV WSBK BOSTON

1170 Soldiers Field Road, Boston, MA 02134

Chief Engineer

file:///M:/pmasucc/Work/General%20Info/email-combo%20logos.jpg

o 617 562-5044

c 617 828-1041

f 617 787-7106

www.cbsboston.com

Then I replied back:

Lenny I wish I had answer for why your reception has degraded recently. We have not been having any trouble with our transmission systems.



Your installation sounds like a good one, though I think it may be a bit overdone, as a high-gain antenna in combination with 28 dB of amplification is probably more than you need, even at that distance. For comparison, I live 43.1 air miles from the transmit antenna, and I use a Channel Master 4228 8-bay bowtie antenna on the roof of my one-story house, with no amplification. I get full-bore signal into the TV on almost all channels. We have had incidences with viewers who had too much amplification in which they lost WBZ and WFXT, which had the most powerful signals in the Boston market (at the time). They were overdriving their TVs and as a result suffering the loss of the two stations they should have received with the least effort.



Wish I had a more definitive answer€¦





Robert Yankowitz, CPBE

WBZ-TV WSBK BOSTON

1170 Soldiers Field Road, Boston, MA 02134

Chief Engineer

file:///M:/pmasucc/Work/General%20Info/email-combo%20logos.jpg

o 617 562-5044

c 617 828-1041

f 617 787-7106

www.cbsboston.com



-------- Original message --------
From: Wufoo
Date: 9/21/16 11:00 PM (GMT-05:00)
To: CBS Local Site Contact Us , "Eich, Julie O"
Subject: General Information - Boston - [#95913]

Name *


Leonard Stein

Email *




Phone Number *


(603) 887-4253

Direct Your Message To CBS Local Staff In... *


Boston

Link (if appropriate)


Please forwaed this to engineering dept.

Comment

For the past ten days or so we have been having problems with TV channel 4. We are located in Chester N.H. about 45 miles (as the crow flies) from the transmitter. The antenna is an old, but in good condition, very high gain Channel Master 5 foot parabolic which is mounted on a tripod about 6 feet off the roof. There is a mast mounted Winegard GA 8780 preamplifier with a 28 DB UHF section along with a very low noise figure mounted about 2 feet from the antenna. The cable is RG6 Quad which goes into a two way splitter. The receiver, (converter box) is a Channel Master 7001. Our elevation is 410 feet and we are surrounded by trees, some deciduous and some pine.

Most of the time, in spite of this not so ideal situation, (location) I can receive the three networks and a few independents. The signal display on the converter shows, as two horizontal bars, "signal quality" and "signal level". On most channels most of the time signal quality is pegged at 100 percent and signal level runs between 45 and 55 percent. Within this window I usually have no problems with reception. As long as signal quality doesn't fold back I usually will get no drop outs. If it should falter excessively though both picture and sound will break up and intermittently freeze. So I'm pretty familiar with what conditions will produce a good signal.

Lately Channel 4 although displaying 54 percent signal level and 100 percent signal quality has had very slight "tearing streaks" going through the picture. If these aberrations only affected the picture we would be able to watch the program. However this problem seems to chop up the sound as well. This makes it impossible to watch a program. I am a TV repair technician and I have never seen this type of choppy sound on either OTA or cable before..

The weather of late has been hot and humid, which is atypical for New England this time of year. I've noticed in the past that during this type of weather we do sometimes lose reception on several channels for a day or two but never this long. I'm just wondering if anyone there might have a theory as to what could be happening here. This only seems to affect channel 4, (where all our shows happen to be). Thanks, Lenny


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Add star Klem Sun, Oct 2, 2016 at 3:55 PM
To: "Yankowitz, Robert B"
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Hi Robert

Thank you for getting back to me. One thing that I failed to mention
is that this is not a new installation. We put this antenna up about
three years ago and it has always seemed to perform well.

I hear what you are saying about overload, and in theory Chester NH is
not such a haul from Boston. TV Fool never mentions the use of an
amplifier for my location relating to Boston, and I have used that
resource a lot to determine whether an antenna job at a certain
location would be feasible or not. The preamp though has always seemed
to make a substantial difference here as well as throughout town. I
had a customer years ago who lived out of town near the top of the
mountain that is partially blocking our South West view. He was
watching everything from Boston including 10 and 12 from Providence,
with rabbit ears. So I've always figured that it must be the foliage
and the terrain that's attenuating my signal.

Before digital, for my own house I used separate VHF and UHF
antennas. We never needed any help with VHF, but UHF was always a
challenge for us. The UHF antenna at the time was an 8 bay. During
this period Winegard had just come out with a commercial preamp that
had slightly lower gain but boasted an unheard of 1DB noise figure. I
had to try this so I ordered one and installed it after the 8 bay. I
pointed it towards Boston but channel 50's transmitter in Hudson NH
splattered across the entire band. Although having a very hot front
end the commercial preamp was not nearly as forgiving of overloads as
the 8780. I eventually put a 20 DB trap set for channel 50 in line and
that solved the overload problem. However in spite of all this, UHF
reception with the 8 bay from Boston was never really very good at our
house.

Since as we all know it's not possible to watch a polar bear in a snow
storm with digital three years ago I realized that I had to do
something. This parabolic which I'm presently using is a 300 ohm
antenna which I had liberated from a job about 20 some odd years ago.
I had always planned to use it "some day" and it had been sitting in
the woods behind my house since. It had a few broken reflectors which
I repaired.I looked up the specs recently on this antenna and it seems
to beat everything out there. Gain is between 13 to 16 DB, but it's
narrow beam width is really where it excels. Early on I had considered
that my problem could possibly be multipath, however just turning this
antenna a few degrees and signal starts to drop like a rock.

We didn't have cable TV here in Chester until the early 1990's, and
back then I used to install quite a few antennas and retrofit existing
ones with preamps. I had a nice Sadelco signal meter that tuned up to
channel 83. I no longer do antenna work so I don't presently have
equipment to measure OTA signals. So now admittedly a lot of this is
an educated guess. Back then most consumer equipment particularly
antennas were 300 ohms, and since the GA8780's input impedance also
was 300 ohms I kind of standardized on this amp for my retrofits as
well as new installations. The noise figure was about 3 DB which was
the best of the time, beating Channel Master's figure of 5. However
the real attraction of this amp was the very forgiving limiter
circuit. I never had one overload on me, including those used in
installations much higher than mine.

So as you might imagine I've been very frustrated with this problem.
However as of five days ago the problem has disappeared. Signal levels
and quality as measured on my converter boxes show no difference, and
if this was weather related we have had varying degrees of weather
through this period as well. We do sometimes experience days at a time
where reception is poor for whatever reason but it's always reflected
on the signal strength and quality indication on the converter box
meter. This was definitely not the case this time though. To the best
of my recollection in this past three years this particular type of
problem has never happened before.

I do have a theory though that I wanted to suggest. The orientation of
my antenna when it is optimized for Boston puts it a few degrees South
East of New York City. Do you think that skip conditions were such
through this period of time that this could possibly have been CO
channel interference from WNBC in New York? As I had previously
mentioned no other channels were affected nor have I noticed anything
unusual on any of the Amateur frequencies or my low band two way
business radio system.

We do occasionally see what I believe must be tropospheric inversion,
and we do seem to experience them at different times of the year.
During these periods, which typically last up to five days, Boston UHF
TV stations that I never can pull in such as 56 and 68 come bombing
in, and many times with 90 percent signal strength. Then as
mysteriously as they appeared, after a period of time they're gone.
This episode however didn't seem to be an inversion, as there were no
newcomers in my channel line up through this time.

In 1975 I decided that I wanted to work in broadcasting. I got my
First and I was hired as a studio technician for a UHF TV station in
Central New York. Much of that work involved translator maintenance. I
still recall (although not fondly) those awful cold trips up the
mountains when the snowmobile wasn't running to service those
miserable things. After that stint I switched careers to military, and
then industrial electronics. I took a hard look at my life after that
and since I had been repairing TV's from the time I was a teenager I
decided to go in for myself. So since 1983 I've operated my own
consumer electronics service business. Now I'm semi retired, (whatever
that means) and I haven't seen the inside of a TV studio no less a
network studio in 45 years. I'm sure much has changed.

I'm sure that you are more than familiar with it than I but I found a
rather interesting article on tropospheric propagation on Wikipedia,
and there was also if you are interested some propaganda on my
antenna.

Thank you very much for trying to help me evaluate this problem. I
appreciate the time and trouble you've taken.
Very truly yours, Lenny Stein, KC1CPX

https://en.wikipedia.org/wiki/Tropospheric_propagation

http://www.rocketroberts.com/cm4251/cm4251.htm

I wanted to include all the background information before this thread began.. Lenny

BTW, here are my coordinates: and although the topo maps said different according to Google my altitude is 115 meters
465 Derry Rd, Chester, NH 03036, USA
Latitude: 42.930838 | Longitude: -71.281921


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On Sunday, November 6, 2016 at 7:40:38 PM UTC-5, wrote:
I tried posting something about this in the past but got no response.


More than likely because you're posting from google groups.

* Killfiling google & XXXXbanter.com: jonz.net/ng.htm
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Jon Elson wrote:
wrote:

I tried posting something about this in the past but got no response. I'm
holing that this time someone might read it who may have a theory as to
what could be going on.

I live in southern New Hampshire and watch OTA TV out of Boston, which is
about 60 miles from here. Lately I as well as several other people I know
have been experiencing intermittent problems with channel four. While most
other channels are presently operating fine, for the past 10 days or so
channel 4's signal has been in the toilet. This station, WBZ TV operates
on UHF channel 30, runs 825KW, and has an antenna height of 390 meters. By
contrast Channel 5, WCVB, operates on UHF channel 20, runs 625 KW, and
shares the same tower and has it's antenna at the same height as channel
4's, and we never have any problems with that channel. Could propagation
be that much different 60 MHZ apart? What is really weird is that the
signal just drops to almost nothing.

I discussed this with the chief engineer at Channel four and he had no
explanation for this. Does anyone have any theories about this? Thanks,
Lenny

Anybody hit or knock down a pole in the area? I assume your neighborhood is
wired for cable. Damage to poles can knock connectors partially loose,
allowing a LOT of signal to flow onto the outer sheath. Could be a signal
right on the same frequency as Chan 4.



Digital CATV uses QAM modulation, not ATSC.


--
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They don't get mad.

They don't get even.

They go for over unity! ;-)
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On Wed, 9 Nov 2016 15:25:58 -0500, "Michael A. Terrell"
wrote:

Jon Elson wrote:
wrote:

I tried posting something about this in the past but got no response. I'm
holing that this time someone might read it who may have a theory as to
what could be going on.

I live in southern New Hampshire and watch OTA TV out of Boston, which is
about 60 miles from here. Lately I as well as several other people I know
have been experiencing intermittent problems with channel four. While most
other channels are presently operating fine, for the past 10 days or so
channel 4's signal has been in the toilet. This station, WBZ TV operates
on UHF channel 30, runs 825KW, and has an antenna height of 390 meters. By
contrast Channel 5, WCVB, operates on UHF channel 20, runs 625 KW, and
shares the same tower and has it's antenna at the same height as channel
4's, and we never have any problems with that channel. Could propagation
be that much different 60 MHZ apart? What is really weird is that the
signal just drops to almost nothing.

I discussed this with the chief engineer at Channel four and he had no
explanation for this. Does anyone have any theories about this? Thanks,
Lenny

Anybody hit or knock down a pole in the area? I assume your neighborhood is
wired for cable. Damage to poles can knock connectors partially loose,
allowing a LOT of signal to flow onto the outer sheath. Could be a signal
right on the same frequency as Chan 4.



Digital CATV uses QAM modulation, not ATSC.


What is your point? His point was that a leaky cable system with
signals on channel 4 could interfere with the OP's over the air
channel 4 signal. That is certainly possible even if different
modulation schemes are used. (And by channel 4, we mean virtual 4 -
RF 30).
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On Thu, 10 Nov 2016 08:08:50 -0500, Pat wrote:

On Wed, 9 Nov 2016 15:25:58 -0500, "Michael A. Terrell"
wrote:

Jon Elson wrote:
wrote:

I tried posting something about this in the past but got no response. I'm
holing that this time someone might read it who may have a theory as to
what could be going on.

I live in southern New Hampshire and watch OTA TV out of Boston, which is
about 60 miles from here. Lately I as well as several other people I know
have been experiencing intermittent problems with channel four. While most
other channels are presently operating fine, for the past 10 days or so
channel 4's signal has been in the toilet. This station, WBZ TV operates
on UHF channel 30, runs 825KW, and has an antenna height of 390 meters. By
contrast Channel 5, WCVB, operates on UHF channel 20, runs 625 KW, and
shares the same tower and has it's antenna at the same height as channel
4's, and we never have any problems with that channel. Could propagation
be that much different 60 MHZ apart? What is really weird is that the
signal just drops to almost nothing.

I discussed this with the chief engineer at Channel four and he had no
explanation for this. Does anyone have any theories about this? Thanks,
Lenny


Anybody hit or knock down a pole in the area? I assume your neighborhood is
wired for cable. Damage to poles can knock connectors partially loose,
allowing a LOT of signal to flow onto the outer sheath. Could be a signal
right on the same frequency as Chan 4.


Digital CATV uses QAM modulation, not ATSC.


What is your point? His point was that a leaky cable system with
signals on channel 4 could interfere with the OP's over the air
channel 4 signal. That is certainly possible even if different
modulation schemes are used. (And by channel 4, we mean virtual 4 -
RF 30).


Besides using different modulation schemes, cable channels are also
interleaved with OTA channels to prevent mutual interference (via
leakage and ingress). For example, broadcast channel 30 goes from
566-572MHz OTA. The closest CATV channel is channel 81, which goes
from 564-570MHz.

Most of the leakage I've seen from CATV systems comes from poor Type-F
coax connector installations by home owners and unterminated coax
cables. It takes quite a bit of cable leakage to produce interference
with an OTA signal, but it might be possible in weak areas and if the
OTA TV system uses a pre-amplifier.



--
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 Tue, 8 Nov 2016 13:56:36 -0800 (PST),
wrote:

On Sunday, November 6, 2016 at 7:40:38 PM UTC-5, wrote:
I tried posting something about this in the past but got no response.

(...)
I wanted to include all the background information before this thread began. Lenny


I can see why you received no response. 357 lines of disorganized
ranting is difficult to parse. Please get organized and save readers
the effort of wading through your mess. Same as always:
1. What problem are you trying to solve? Keep it very simple.
2. What equipment do are you using? Numbers and details are good.
3. What have you done so far and what happened?

I'm busy for a few days and will hopefully do a path profile this
weekend. I don't know if I can squeeze much out of the path analysis
except that you might have some obstructions or Fresnel zone
diffraction problems. From the plots I previously posted, the
coverage of both stations look identical.

Did you do any of the substitution tests that I recommended? The best
test would be just the TV, a length of RG-6/u, and a simple 1/2 wave
(at 500MHz) dipole hund outside the window. No amps or splitters.

Did you run your address through TVfool.com to see what signal levels
they predict?

BTW, here are my coordinates: and although the topo maps said
different according to Google my altitude is 115 meters


Slight misunderstanding. I need the type of antenna you are using at
your house, and its elevation above ground level. You can save me
some trouble excavating the information from your archive by listing
everything (inclusive) between the antenna and the TV receiver.

465 Derry Rd, Chester, NH 03036, USA
Latitude: 42.930838 | Longitude: -71.281921


Thanks for using a decent (decimal degrees) format. I hate DMS.

From the FCC data, WBZ is at 42° 18' 37.00" N, 71° 14' 14.00" W
but in NAD27. Converting the FCC DMS to decimal and datum into WGS84:
(42.310278 N, -71.237222W) NAD27 - (42.31025 N, 71.23669 W) WGS84.
Antenna height above ground 387 meters (1270 ft).
Nice little monster tower:
http://www.necrat.us/bztower.html

Well, I have a few minutes I'll throw together a Google Earth path
profile. It won't be very accurate and won't show Freznel zones, but
will show any obstructions. Looks like drawing a 1270ft tower is
gonna be difficult, so I guessed:
http://802.11junk.com/jeffl/coverage/KBCZ-WBZ/WBZ-Lenny.jpg
If you have Google Earth, here's the PRELIMINARY KMZ file:
http://802.11junk.com/jeffl/coverage/KBCZ-WBZ/WBZ%20path.kmz
Looks like you have a rather large hill directly in the path and very
close to you. A 150ft or so tower at your end would be needed to
clear the hill.


Incidentally, I vaguely recall a similar OTA problem where one channel
was uncharacteristically low in receive signal. It turned out to be
an unterminated length of coax on a coaxial splitter. Even though the
splitter was suppose to have perhaps 20dB(?) of isolation between
ports, the device was so badly built that I'm sure it was much less.
http://802.11junk.com/jeffl/crud/CATV-splitters.jpg
The unterminated length acted as a notch filter which just happened to
land on the TV channel frequency. Replacing the spllitter and
removing the coax or terminating it with 75 ohms solved the problem.

--
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:


Most of the leakage I've seen from CATV systems comes from poor Type-F
coax connector installations by home owners and unterminated coax
cables. It takes quite a bit of cable leakage to produce interference
with an OTA signal, but it might be possible in weak areas and if the
OTA TV system uses a pre-amplifier.



The OP is definitly in a weak area (45 miles from stations) and IS using an
aplifier just under the antenna. Anybody within a fe miles in the general
direction of the broadcast antenna could be trashing his signal. Without
the proper equipment (portable spectrum analyzer), it could be quite hard to
find the problem.

Jon
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On Thu, 10 Nov 2016 14:40:12 -0600, Jon Elson
wrote:

The OP is definitly in a weak area (45 miles from stations) and IS using an
aplifier just under the antenna.


Yep, and there's another problem:
http://802.11junk.com/jeffl/coverage/KBCZ-WBZ/WBZ-Lenny.jpg
That a really rough and crude guestimate of the path, which shows a
150ft pile of dirt blocking the signal. It could be knife edge
diffraction, but I don't think so. My guess(tm) is some part of his
system (antenna, amp, coax, splitter, power injector, TV) is broken.

Anybody within a few miles in the general
direction of the broadcast antenna could be trashing his signal.


Yep. I didn't check for other UHF TV stations in his area. Overload
(blocking) is possible, but usually affects ALL the channels. Since I
determined that the theoretical signal strength from both WBZ and KVCB
are almost identical, I don't see a nearby signal trashing one signal,
but not the other. The lack of complaints about other channels also
points to a specific problem on UHF channel 30.

Without
the proper equipment (portable spectrum analyzer), it could be quite hard to
find the problem.


Test equipment is always nice to have. However, I think this one can
be nailed by simply substituting parts of the puzzle and comparing the
effects on both WBZ and KBCZ. When something is replaced that makes
the signals equal, then the problem has been found.

However, if you really want to use a portable spectrum analyzer, any
of the RTL2832U SDR receiver dongles make a nifty spectrum analyzer.
http://www.rtl-sdr.com/?s=spectrum+analyzer
I run several RTL-SDR programs on my Google Nexus 7 tablet that acts
something like a spectrum analyzer.
https://play.google.com/store/apps/details?id=marto.androsdr2
The basic sensitivity of the typical USB SDR dongle sucks without an
RF preamp, but should be good enough to see what's arriving from the
antenna mounted amplifier.

--
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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Pat wrote:
On Wed, 9 Nov 2016 15:25:58 -0500, "Michael A. Terrell"
wrote:

Jon Elson wrote:
wrote:

I tried posting something about this in the past but got no response. I'm
holing that this time someone might read it who may have a theory as to
what could be going on.

I live in southern New Hampshire and watch OTA TV out of Boston, which is
about 60 miles from here. Lately I as well as several other people I know
have been experiencing intermittent problems with channel four. While most
other channels are presently operating fine, for the past 10 days or so
channel 4's signal has been in the toilet. This station, WBZ TV operates
on UHF channel 30, runs 825KW, and has an antenna height of 390 meters. By
contrast Channel 5, WCVB, operates on UHF channel 20, runs 625 KW, and
shares the same tower and has it's antenna at the same height as channel
4's, and we never have any problems with that channel. Could propagation
be that much different 60 MHZ apart? What is really weird is that the
signal just drops to almost nothing.

I discussed this with the chief engineer at Channel four and he had no
explanation for this. Does anyone have any theories about this? Thanks,
Lenny
Anybody hit or knock down a pole in the area? I assume your neighborhood is
wired for cable. Damage to poles can knock connectors partially loose,
allowing a LOT of signal to flow onto the outer sheath. Could be a signal
right on the same frequency as Chan 4.


The connectors on the trunklines and feeders are 5/8-27 thread, and
are quite strong. The housings have a pressed in stainless steel insert
so the threads don't strip out easily. Also, the 60VAC @30A, modified
square wave that powers the trunk and bridging amplifiers is carried on
the rigid coax. If it is loose enough t radiate, it will have a high
enough resistance to prevent the amplifier from working. The RayChem
heatshrink ceramic connectors we used in the mid '80s were so strong
that the outer aluminum tubing would break, instead of the connector to
shield connection.


Digital CATV uses QAM modulation, not ATSC.


What is your point? His point was that a leaky cable system with
signals on channel 4 could interfere with the OP's over the air
channel 4 signal. That is certainly possible even if different
modulation schemes are used. (And by channel 4, we mean virtual 4 -
RF 30).



Different modulation systems would not mesh, and cause a weak signal
from phase reversal. Download the Blonder Tongue Design Guide, and read
it. CATV systems rarely carried A TV station on the same channel that it
was transmitted on. For instance, United Video in Cincinnati, had custom
labels for their converters. Instead of Ch 2 to 37, they were labeled 1
to 36. So, Channel 12 was actually on Ch 13 to prevent problems with
direct pickup. The actual Ch. 12 carried one of our in house generated
channels.


http://www.blondertongue.com/UserFiles/file/documents/2012%20BRG%20FINAL_lo-res.pdf


--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)
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On Sat, 12 Nov 2016 06:32:48 -0500, "Michael A. Terrell"
wrote:

http://www.blondertongue.com/UserFiles/file/documents/2012%20BRG%20FINAL_lo-res.pdf


Thanks, but the 2014 version is more current:
http://www.blondertongue.com/UserFiles/file/Marketing%20Literature/2014_BRG_lo-res.pdf
Other documents and catalogs might be of interest:
http://www.blondertongue.com/about/request_a_catalog.aspx

--
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, 12 Nov 2016 06:32:48 -0500, "Michael A. Terrell"
wrote:

http://www.blondertongue.com/UserFiles/file/documents/2012%20BRG%20FINAL_lo-res.pdf



I have several other dates archived, as well. Sometimes you need the
older information for existing systems.


Thanks, but the 2014 version is more current:
http://www.blondertongue.com/UserFiles/file/Marketing%20Literature/2014_BRG_lo-res.pdf
Other documents and catalogs might be of interest:
http://www.blondertongue.com/about/request_a_catalog.aspx



Several other companies had useful publications, but the slow
conversion to Fiber Aided CATV killed them off.


--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)


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On Sat, 12 Nov 2016 23:25:15 -0500, "Michael A. Terrell"
wrote:

Jeff Liebermann wrote:
On Sat, 12 Nov 2016 06:32:48 -0500, "Michael A. Terrell"
wrote:

http://www.blondertongue.com/UserFiles/file/documents/2012%20BRG%20FINAL_lo-res.pdf


I have several other dates archived, as well. Sometimes you need the
older information for existing systems.


Good point (after I erased the 2012 version from my machine).
I did some Googling and found the 2008 version of the Blonder Tongue
guide at:
https://www.sateng.com/downloads/btbroadbandrefguide.pdf
After a quick glance, it seems to have quite a bit on antenna systems,
which are not used very much these days thanks to fiber and satellite
backhauls.

Also, the 2009 version at:
http://www.blondertongue.com/UserFiles/file/documents/2009%20BBand%20Ref%20Guide.pdf

Thanks, but the 2014 version is more current:
http://www.blondertongue.com/UserFiles/file/Marketing%20Literature/2014_BRG_lo-res.pdf
Other documents and catalogs might be of interest:
http://www.blondertongue.com/about/request_a_catalog.aspx


Several other companies had useful publications, but the slow
conversion to Fiber Aided CATV killed them off.


The Motorola (now Arris) 2014 guide is what I like to use:
https://www.arris.com/globalassets/resources/other/cable_technology_pocket_guide.pdf
(6MB) 302 pages.


--
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, 12 Nov 2016 23:25:15 -0500, "Michael A. Terrell"
wrote:

Jeff Liebermann wrote:
On Sat, 12 Nov 2016 06:32:48 -0500, "Michael A. Terrell"
wrote:

http://www.blondertongue.com/UserFiles/file/documents/2012%20BRG%20FINAL_lo-res.pdf


I have several other dates archived, as well. Sometimes you need the
older information for existing systems.


Good point (after I erased the 2012 version from my machine).
I did some Googling and found the 2008 version of the Blonder Tongue
guide at:
https://www.sateng.com/downloads/btbroadbandrefguide.pdf
After a quick glance, it seems to have quite a bit on antenna systems,
which are not used very much these days thanks to fiber and satellite
backhauls.

Also, the 2009 version at:
http://www.blondertongue.com/UserFiles/file/documents/2009%20BBand%20Ref%20Guide.pdf

Thanks, but the 2014 version is more current:
http://www.blondertongue.com/UserFiles/file/Marketing%20Literature/2014_BRG_lo-res.pdf
Other documents and catalogs might be of interest:
http://www.blondertongue.com/about/request_a_catalog.aspx


Several other companies had useful publications, but the slow
conversion to Fiber Aided CATV killed them off.


The Motorola (now Arris) 2014 guide is what I like to use:
https://www.arris.com/globalassets/resources/other/cable_technology_pocket_guide.pdf
(6MB) 302 pages.



Just like early electrical engineering books that explained the
things that are just glossed over in current books. P Millet's website
is a wealth of early electronics books.


--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)
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On Sun, 13 Nov 2016 15:53:54 -0500, "Michael A. Terrell"
wrote:

Just like early electrical engineering books that explained the
things that are just glossed over in current books. P Millet's website
is a wealth of early electronics books.


Yep.
http://www.tubebooks.org/technical_books_online.htm
I downloaded a mess of those (mostly radio books) a few years ago and
amd sloooowly going through them. What's interesting to me is that
the origins or reasons behind various modern technical decisions and
standards can be found in the old books.

However, I doubt any of this will help deal with the current OTA TV
reception problem. I'm not getting any response from CaptainVideo so
I guess I'll drop the project for now.

--
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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captainvideo:

Your problem is two-fold: distance, and
the all-digital broadcast requirement.


8 years ago, on NTSC(analog), distance
would not have been been such an issue.
You probably would have had snow on
a lot of channels, but you still had picture
and sound.


Now, on ATSC(digital), you don't get certain
stations at all, and frequent dropouts on
others.

This is why I maintain that ATSC is 'less
Green' than NTSC was: While with
digital stations can piggy-back channels
(4.2, 4.3, 4.4, etc.) they must BOOST
THEIR SIGNAL for people with same
OTA setup to receive them in the first
place. And increasing signal strength
meansUSING MORE ENERGY - something
the folks over at Alt.Video.Digital.Tv fail
to grasp.

You said you are using a 'parabolic' antenna
currently - I'm assuming that is dish-shaped.

Have you looked into a variation on this
form factor yet? It's all I'll ever use, even
just 35 miles away from my market:

https://m.lowes.com/pd/Channel-Maste...0-f2260ea5c961

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Pat wrote: "You may fail to grasp it, too. When you hear about TV stations
(especially UHF stations) using millions of watts of power, they are
referring to ERP - Effective Radiated Power. That means the actual
power going into the antenna is much lower but the antenna has very
high gain. Rarely do stations use more than a few thousand watts of
actual power. The transmitter's actual power usage is a drop in the
bucket compared to all the other energy a TV station uses for lights,
cameras, HVAC, etc. "

________
Alright, say a typical medium market
station has historically transmitted
2,000W as a NTSC. 2009 they go
fully ATSC, still at 2,000W. Hundreds
of letters from viewers flood their
mailbox, and thousands of callers
jam their phone boards about not
being able to pick them up over the
air with their new TVs. Most are from
viewers in the outer one-third of the
station's transmission radius.


Station board deliberates, and
after a couple months decides to
increase transmitter wattage to 2,500W.
Viewer complaints plummet, while
greenhouse gas emmissions steadily
rise to generate additional electricity as
this scenario is mulitiplied across dozens
of medium markets and many major
markets.

Grasp that!


Yeah, I get that actual wattage is but
a fraction of ERP, but it still adds up
as many TV stations must increase their
signal strength to cover the same
audience area in digital as they did
via analog.
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On Tue, 15 Nov 2016 08:31:32 -0800 (PST),
wrote:

Pat wrote: "You may fail to grasp it, too. When you hear about TV stations
(especially UHF stations) using millions of watts of power, they are
referring to ERP - Effective Radiated Power. That means the actual
power going into the antenna is much lower but the antenna has very
high gain. Rarely do stations use more than a few thousand watts of
actual power. The transmitter's actual power usage is a drop in the
bucket compared to all the other energy a TV station uses for lights,
cameras, HVAC, etc. "

________
Alright, say a typical medium market
station has historically transmitted
2,000W as a NTSC. 2009 they go
fully ATSC, still at 2,000W. Hundreds
of letters from viewers flood their
mailbox, and thousands of callers
jam their phone boards about not
being able to pick them up over the
air with their new TVs. Most are from
viewers in the outer one-third of the
station's transmission radius.


Station board deliberates, and
after a couple months decides to
increase transmitter wattage to 2,500W.
Viewer complaints plummet, while
greenhouse gas emmissions steadily
rise to generate additional electricity as
this scenario is mulitiplied across dozens
of medium markets and many major
markets.

Grasp that!


Don't forget the part where they have to modify their license at the
FCC after hiring engineers to show that the increased power doesn't
cause interference with any other licensed station in the area (or in
Canada). That process can takes a long time and is expensive even
before equipment is purchased. Most of the applications are on hold
right now waiting for the auctions to be complete. ATSC has lots of
issues, but creating a significant increase in greenhouse gases isn't
one of them.



Yeah, I get that actual wattage is but
a fraction of ERP, but it still adds up
as many TV stations must increase their
signal strength to cover the same
audience area in digital as they did
via analog.

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On 18/11/16 13:44, Michael A. Terrell wrote:
Pat wrote:
Solid state transmitters are modular, with around 1KW output, per
tray. Look at the Harris Broadcast website for some actual data.


I have a half-dozen such modules here, unfortunately
with the water-cooled heatsink removed, if you want
photos or to ask any questions. The modules are single
or dual, using a BLF278 dual FET each. A 30W input is
split into six to drive three duals, which are then
combined to produce about 1KW from about 6KW input at
50V. The power supply rectifies three-phase 415V mains
and chopped it to produce 50V at 60A, scary.

A local ATV transmitter was using more than 50 of these
to put 50KW up the spout. Pretty old-tech now though,
the new lateral MOSFETs from NXP produce 1500W from a
single device (two FETs), as Michael T has pointed out
recently.

The really interesting bit to me is how simple the baluns
are - just a couple of 8cm lengths of special hardline
to match from about 12 ohms up to 50, at 225MHz.
Transmission line transformers FTW! There's quite a few
reference designs for this class of transmitter at
http://nxp.com

Clifford Heath.


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Clifford, Michael:

So you're saying modern ATSC transmitters
actually use less power then the old NTs?
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On Fri, 18 Nov 2016 15:06:37 -0600, amdx wrote:

On 11/15/2016 11:09 AM, Jeff Liebermann wrote:
On Sun, 6 Nov 2016 16:40:35 -0800 (PST),
wrote:
(...)

This is too easy.
WBZ has been running on reduced power for most of the last few weeks
thanks to an antenna problem:
http://boston.cbslocal.com/2016/11/07/wbz-tv-wsbk-tv-operating-at-reduced-power/
http://boston.cbslocal.com/2016/10/22/transmission-issue-causes-outage-for-some-wbz-tv-viewers/
No clue if it has been fixed, but judging by the lack of updates,
probably not.


Well that takes all the fun out of it!


Occam's Razor.

But do note my post of good reception at 51.9m miles with
cut to length folded dipole, 10 ft off the ground.
Channel 36, about 9.5" long.
Mikek


Sure, it can be done at 45 miles depending on tx power and frequency.
However, Captain Video has an additional problem in the form of a
mound of dirt in between his antenna and the station transmitter.
http://802.11junk.com/jeffl/coverage/KBCZ-WBZ/WBZ-Lenny.jpg
or if you have Google Earth handy:
http://802.11junk.com/jeffl/coverage/KBCZ-WBZ/WBZ%20path.kmz
The above path profile is NOT very accurate. I stopped working on the
problem after Captain Video disappeared from the thread.

Incidentally, I sometimes can watch KMPH TV from Fresno, CA which is
about 200 miles away from Ben Lomond. I live on the side of a hill
which helps. The real culprit is atmosheric ducting and edge
diffraction from two mountain ranges in between. It only happens a
few days per year, usually in the summer, but the picture is 100%
perfect.


--
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 11/18/2016 5:02 PM, Jeff Liebermann wrote:
On Fri, 18 Nov 2016 15:06:37 -0600, amdx wrote:

On 11/15/2016 11:09 AM, Jeff Liebermann wrote:
On Sun, 6 Nov 2016 16:40:35 -0800 (PST),
wrote:
(...)

This is too easy.
WBZ has been running on reduced power for most of the last few weeks
thanks to an antenna problem:
http://boston.cbslocal.com/2016/11/07/wbz-tv-wsbk-tv-operating-at-reduced-power/
http://boston.cbslocal.com/2016/10/22/transmission-issue-causes-outage-for-some-wbz-tv-viewers/
No clue if it has been fixed, but judging by the lack of updates,
probably not.


Well that takes all the fun out of it!


Occam's Razor.

But do note my post of good reception at 51.9m miles with
cut to length folded dipole, 10 ft off the ground.
Channel 36, about 9.5" long.
Mikek


Sure, it can be done at 45 miles depending on tx power and frequency.
However, Captain Video has an additional problem in the form of a
mound of dirt in between his antenna and the station transmitter.
http://802.11junk.com/jeffl/coverage/KBCZ-WBZ/WBZ-Lenny.jpg
or if you have Google Earth handy:
http://802.11junk.com/jeffl/coverage/KBCZ-WBZ/WBZ%20path.kmz
The above path profile is NOT very accurate. I stopped working on the
problem after Captain Video disappeared from the thread.

Incidentally, I sometimes can watch KMPH TV from Fresno, CA which is
about 200 miles away from Ben Lomond. I live on the side of a hill
which helps. The real culprit is atmosheric ducting and edge
diffraction from two mountain ranges in between. It only happens a
few days per year, usually in the summer, but the picture is 100%
perfect.


When I was a lot younger living in Kalamazoo Michigan, late one night
I received a Wisconsin TV station across lake Michigan.

Mikek


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Michael Terrell wrote: - hide quoted text -
wrote:
Clifford, Michael:

So you're saying modern ATSC transmitters
actually use less power then the old NTs?



"The heaters in Klystons used a lot of power, that had to be removed as
heat, in a water chiller. One 25 KW UHF transmitter that I rebuilt used
a pair of 1.5V, 1000A heaters per tube. That was 3 KW, then the fan on
the water chiller was a 480V, three phase, 5 hp motor. The circulating
pump was anther two HP. None of this ended up at the output port. "
- show quoted text -


That doesn't answer my question of whether
or not AT transmitters use less power than
NT. Just a simple Yes or No would suffice.
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On Saturday, November 19, 2016 at 2:52:21 AM UTC-5, wrote:
Michael Terrell wrote: - hide quoted text -
wrote:
Clifford, Michael:

So you're saying modern ATSC transmitters
actually use less power then the old NTs?



"The heaters in Klystons used a lot of power, that had to be removed as
heat, in a water chiller. One 25 KW UHF transmitter that I rebuilt used
a pair of 1.5V, 1000A heaters per tube. That was 3 KW, then the fan on
the water chiller was a 480V, three phase, 5 hp motor. The circulating
pump was anther two HP. None of this ended up at the output port. "
- show quoted text -


That doesn't answer my question of whether
or not AT transmitters use less power than
NT. Just a simple Yes or No would suffice.


there is not a simple answer..

if the station stayed on the same frequency, then it can use lower power digital compared to analog. Digital fundamentally requires less power to close the link.

HOWEVER.

many stations also switched from a VHF frequency to a UHF frequency.
The FCC allows more power to be used on UHF.

So in each case the answer is ...it depends.

I think it would be a gross exaggeration to say that digital TV is environmentally more friendly compared to analog because of power consumption.

m

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