Taxi CB on my speaker (1975)

What happened when a taxi's CB could be heard on my powerless home stereo speaker (ca 1975)?
                 - = - Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist          http://www.panix.com/~vjp2/vasos.htm ---{Nothing herein constitutes advice. Everything fully disclaimed.}--- [Homeland Security means private firearms not lazy obstructive guards] [Urb sprawl confounds terror] [Phooey on GUI: Windows for subprime Bimbos]
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On 5/17/15 2:10 PM, snipped-for-privacy@at.BioStrategist.dot.dot.com wrote:

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.
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Would wrapping aluminum foil around the speaker help? Is it worth a try?
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On Sun, 17 May 2015 18:10:51 +0000 (UTC), snipped-for-privacy@at.BioStrategist.dot.dot.com wrote:

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!
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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
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On 05/17/2015 10:15 PM, gregz wrote:

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.
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On Sun, 17 May 2015 15:16:29 -0500, snipped-for-privacy@spamblocked.com wrote in

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?
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There is no legal power amp. Might check quality with a spectrum analyzer. Louder, stronger signal.
Greg
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<stuff snipped>

Loved who? (-:

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.
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