OT: C.B. Through My Stereo

[Ash]

The other day I awoke at around 9 am.
I wasn't fully awake so I lied there for about 10 minutes trying to "wake up all the way".

All of a sudden I heard CB transmissions loud & clear.
I was thinking, "What the hell is that and where is it coming from?"

It sounded like it was coming from my stereo that sits atop my entertainment center.

I listened for a few more minutes and then got up and approached my stereo.
Sure enough, the 2-way CB conversation I was hearing was coming directly from my speakers connected to the stereo.

The only thing was that my stereo was turned off.

I listened for about 5 more minutes before it just stopped altogether.
It happened again later that day.
Since I had never heard of anything like this happening before I was kind of baffled at first and the whole thing seemed surreal especially because I wasn't fully awake when it first started.
It kind of tripped me out there for a few minutes!

I'm not real big into the inner workings of how certain electronic devices work but I figure that there's a rational explanation as to why it did that.

How can I receive CB transmissions through my stereo when it is turned off?



Post Edited (04-26-04 01:22)

[Bgrade]

Speakers will do this.  (don't know why)

I used to get this through my computer speakers every couple of weeks when i worked near the freeway.

It always creeps me out.

[ulthar]

CB transmissions are AM, which means the voice signal is an amplitude modulation on the RF carrier.  Basically, what that means is that the oscillations of the carrier 'sine wave' vary in size according to the oscillations of the voice signal.

Demodulating this signal is very easy; in fact, a simply AM detector is nothing more than a single diode in line with the antenna - speaker circuit.  The voice signal drives the speaker directly, in other words.

So, your speaker wires were acting like an antenna, there may be something acting like a rectifier in your speaker (between the wire "antenna" and the voice coil), and the speaker itself is all that is needed to detect AM signals.

Usually, this won't work, since there are many, many AM signals flooding the 'antenna' and all you'd get is white noise.  In an AM radio, there is a 'tank' circuit that selects the RF carrier you want; all other are thrown away.  However, all that is required is that ONE RF signal be large enough to (a) be detected at all, and (b) be much stronger than the others.

The bottom line is that for this signal to have been detected passively through your speaker wires, the signals would have had to be very, very strong.

I suspect you have some folks nearby using high power CB equipment; alternatively, it COULD HAVE BEEN shortwave, not CB at all.  CB is regulated to a max of 4 watts (iirc).  In any case, FCC regulations require ALL radio equipment to not interfere with 'others.'  If this becomes a nuisance to you (more than just a curiosity), you can report it; if they were transient, it won't matter, but if it is someone nearby, they would probabyl get fined  and/or have their radio equipment confiscated.

[Mr. Hockstatter]

That can happen when you play electric guitar and use unshielded cable to connect to your amp.  The output of the guitar is very low (just steel strings vibrating over a small magnet), and not much stronger than a strong radio station.  So if you use unshielded cable, you can have radio stations coming through your amp.

[daveblackeye15]

Don't listen to these fools! It's obvious that your house is haunted! Don't let the ghost eat you! Anyway something similar to this has happened to me: I was watching Futurama and my brother came in and said we had to go. I turn off the t.v. and for a few second I heard Bender say a few lines. I looked at my brother ,who had these wide eyse, then looked back at the t.v. I showed my friend this and he said it happens with the band equipment but I was never really worried.

[raj]

ulthar wrote:

> I suspect you have some folks nearby using high power CB
> equipment; alternatively, it COULD HAVE BEEN shortwave, not CB
> at all.  CB is regulated to a max of 4 watts (iirc).  In any
> case, FCC regulations require ALL radio equipment to not
> interfere with 'others.'  If this becomes a nuisance to you
> (more than just a curiosity), you can report it; if they were
> transient, it won't matter, but if it is someone nearby, they
> would probabyl get fined  and/or have their radio equipment
> confiscated.

I had this happen to me a few times back in upstate New York, but that was with the stereo on.  My roommate would step outside and tell them to shut the f**k up.  That worked, but there were sometimes I had to redo a tape dubbing.  If the FCC is good for anything, it should be for this.

[Ash]

How far away do you think these people with the high power equipment might be from me?

One block?  

Two blocks?

Would they keep their antenna on top of their house where I could easily spot it?
I'm thinking of going looking for a large antenna on the nearby houses.

I feel this weird compulsion to know the source of this signal.
I have to know where it's coming from.

[raj]

For me, they were next door neighbors.  IIRC, they had a big antenna on their house.  That might be clue #1, look around to see if there's a big antenna on top of a house nearby.

[ulthar]

raj wrote:

> For me, they were next door neighbors.  IIRC, they had a big
> antenna on their house.  That might be clue #1, look around to
> see if there's a big antenna on top of a house nearby.

Yeah, but do be careful.  Once you start looking, you will likely see a LOT of antennae around you did not notice before.  Shortwaves are quite common, well, especially in this area.  You don't want to go wrongly accusing people of stuff.

If you do feel compelled to contact the FCC, they can track the signal to its source (meaning, of course, the antenna) pretty easily, especially if it is that strong.

[JohnL]

>I feel this weird compulsion to know the source of this signal.
>I have to know where it's coming from.

Borrow a CB, and the next time you hear it, scan the channels until you find which one it's on. Then you can start talking to them. Invest a little time, get to know them over the CB and then you can convince them that you should get together. Then you'll know who they are and where they live. Of course if it's actually shortwave, you'll have to put in a lot more time and effort...

[Bgrade]

JohnL wrote:

> >I feel this weird compulsion to know the source of this
> signal.
> >I have to know where it's coming from.
>
> Borrow a CB, and the next time you hear it, scan the channels
> until you find which one it's on. Then you can start talking to
> them. Invest a little time, get to know them over the CB and
> then you can convince them that you should get together. Then
> you'll know who they are and where they live.

 Let us know if you need help disposing of the bodies.

[JohnL]

>Let us know if you need help disposing of the bodies.

Come on, let's not get carried away! We haven't even discussed methods of 'eliminating' them yet...