What happened when a taxi's CB could
be heard on my powerless home stereo
speaker (ca 1975)?


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Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist
http://www.panix.com/~vjp2/vasos.htm
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On 5/17/15 2:10 PM, wrote:
What happened when a taxi's CB could
be heard on my powerless home stereo
speaker (ca 1975)?


- = -

The speakers were not shielded enough to prevent the taxi's radio
transmissions being picked up. The speaker's "voice coil" acts similar
to a crystal radio, and rectifys the RF signal into audio.

When I had a CB base station at home in the late 70's, my neighbors
would sometimes hear me transmitting ;-)

Common problem with RF energy.

On Sun, 17 May 2015 14:31:41 -0400, Retired wrote
in

On 5/17/15 2:10 PM, wrote:
What happened when a taxi's CB could
be heard on my powerless home stereo
speaker (ca 1975)

The speakers were not shielded enough to prevent the taxi's radio
transmissions being picked up. The speaker's "voice coil" acts similar
to a crystal radio, and rectifys the RF signal into audio.

When I had a CB base station at home in the late 70's, my neighbors
would sometimes hear me transmitting ;-)

Common problem with RF energy.

Would wrapping aluminum foil around the speaker help? Is it worth a
try?
--
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and having to visit 10 different news stands to pickup each one.
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On Sun, 17 May 2015 18:10:51 +0000 (UTC),
wrote:


What happened when a taxi's CB could
be heard on my powerless home stereo
speaker (ca 1975)?



If it was a taxi, it was probably not a CB, but a business band radio.
However some of those old business band radios were close to the CB
frequencies.

Except for CB, which is niot used much anymore, the business band radios
are mostly all changed to a higher and narrower band now, and many just
use a cellphone these days.

However, back in the 70's when CB was real popular, and many kids had
them, (often with illegal power boosters), they could be a problem on a
home stereo and other eleectronic devices.

At that time, I loved in a large city and very near a freeway. Many
times I would hear truckers on their CB and a local "kid" with his large
illegal CB amp coming thru my stereo speakers. Even my own car CB radio
with legal power, would come thru my stereo is my car was parked right
outside my house.

There was a simple solution. Replace the standard speaker wires with a
shielded cable. Connect the + (pos) speaker wire to the center wire,
connect the - (neg) wire to the shield. Then ground the shield to an
actual ground, which in my case was a well grounded steel water pipe.

That eliminated 95% of the problem. The freeway truckers were gone, and
the nearby kid was gone too. About the only time there was still a
little "leakage" was when I'd key up my own CB, or someone else would do
the same thing, *right next to my house*.

The speakers themselves are not likely to pick up the signal, it's the
wires that acted as antennas!

THere was a way to also add capacitors across the speaker terminals, but
I never did that. Some of the old 70's popular electronics magazines had
more into about this. Most if not all of those magazines are now online
as PDF files to download.

About the only CB users these days are a few old truckers, so unless you
live right next to a major highway, I doubt CD interference should be a
problem anymore!

wrote:
On Sun, 17 May 2015 18:10:51 +0000 (UTC),
wrote:


What happened when a taxi's CB could
be heard on my powerless home stereo
speaker (ca 1975)?



If it was a taxi, it was probably not a CB, but a business band radio.
However some of those old business band radios were close to the CB
frequencies.

Except for CB, which is niot used much anymore, the business band radios
are mostly all changed to a higher and narrower band now, and many just
use a cellphone these days.

However, back in the 70's when CB was real popular, and many kids had
them, (often with illegal power boosters), they could be a problem on a
home stereo and other eleectronic devices.

At that time, I loved in a large city and very near a freeway. Many
times I would hear truckers on their CB and a local "kid" with his large
illegal CB amp coming thru my stereo speakers. Even my own car CB radio
with legal power, would come thru my stereo is my car was parked right
outside my house.

There was a simple solution. Replace the standard speaker wires with a
shielded cable. Connect the + (pos) speaker wire to the center wire,
connect the - (neg) wire to the shield. Then ground the shield to an
actual ground, which in my case was a well grounded steel water pipe.

That eliminated 95% of the problem. The freeway truckers were gone, and
the nearby kid was gone too. About the only time there was still a
little "leakage" was when I'd key up my own CB, or someone else would do
the same thing, *right next to my house*.

The speakers themselves are not likely to pick up the signal, it's the
wires that acted as antennas!

THere was a way to also add capacitors across the speaker terminals, but
I never did that. Some of the old 70's popular electronics magazines had
more into about this. Most if not all of those magazines are now online
as PDF files to download.

About the only CB users these days are a few old truckers, so unless you
live right next to a major highway, I doubt CD interference should be a
problem anymore!

I fixed a lady's stereo once with a cap filter on amp output, for local am
radio interference. I don't know what cab would use am cb. You can't hear
fm usually.
Ferrite core would probably work on amp outs.

Greg

On Sun, 17 May 2015 15:16:29 -0500, wrote in


Many
times I would hear truckers on their CB and a local "kid" with his large
illegal CB amp coming thru my stereo speakers.

Just curious. I don't know anything about CB. How can you tell from
listening to the interference if it comes from an illegal CB amp vs.
just a regular CB amp? If it's just louder, how can you tell the
difference between a legal amp close by vs an illegal amp further
away?
--
Web based forums are like subscribing to 10 different newspapers
and having to visit 10 different news stands to pickup each one.
Email list-server groups and USENET are like having all of those
newspapers delivered to your door every morning.

wrote in message

stuff snipped

At that time, I loved in a large city and very near a freeway.

Loved who? (-:

Many times I would hear truckers on their CB and a local "kid" with his
large illegal CB amp coming thru my stereo speakers.

What amazed me is that the CB of one particular over-amped trucker came
through my speakers when the stereo was turned off and then even unplugged.

Oddly, it was just this one set of speakers, among many, that picked up the
CB signal - I assume it was some odd resonance in the speaker coils or
circuitry. I do remember being pretty amazed that a pretty loud sound was
coming out of speakers that were connected to an amp that was disconnected
from the outlet.

I would have disconnected the speakers, too, but the sound, which appeared
about once every two weeks, eventually disappeared. It's pretty hard to
troubleshoot a problem that only shows up a few times a month.

I call it a "sound" because although it was clearly a person's voice, it was
so distorted it sounded very disturbing (I woke up to it the first time). I
knew it was CB because the phrase "10-4 Good Buddy" has to get pretty
distorted before it's unrecognizable.

--
Bobby G.

On 05/17/2015 10:15 PM, gregz wrote:
I fixed a lady's stereo once with a cap filter on amp output, for local am
radio interference. I don't know what cab would use am cb. You can't hear
fm usually.

I had a system that would pick up the FM broadcasts of the local FM
station. I figured it was the high impedance cartridge in the turntable
that got bored when it wasn't doing its job.

CRNG wrote:
On Sun, 17 May 2015 15:16:29 -0500, wrote in


Many
times I would hear truckers on their CB and a local "kid" with his large
illegal CB amp coming thru my stereo speakers.

Just curious. I don't know anything about CB. How can you tell from
listening to the interference if it comes from an illegal CB amp vs.
just a regular CB amp? If it's just louder, how can you tell the
difference between a legal amp close by vs an illegal amp further
away?

There is no legal power amp. Might check quality with a spectrum analyzer.
Louder, stronger signal.

Greg