Any HAM or CB Radio experts?

[Proneax]

I'm having a strange issue.

My computer speakers are picking up someone's radio signal. I can hear 1 end of the conversation and it is somewhat faint, but I can also hear a 'squelch' like they are releasing a PTT button.

Also, specifically while the person is talking, my RF mouse stops working! ie, if I move my mouse back and forth across the screen and then they start talking, my mouse cursor stops moving even though I am still moving the mouse I have an old MX700 and the receiver is sitting on my desk about 20" away from the mouse.

I could also hear this through the stereo system in my living room. Both setups have unshielded speaker wire running parallel to each other (ie both are running north-south).


MY QUESTION:

Is it possible or probable that someone operating at legal output limits could interfere with the operation of my mouse while transmitting? Or is this an example of an extremely high output?

 

[BlindedByScience]

It could be someone operating at legal limit with a very poor system ground. Keep in mind that for licensed ham operators, the legal limit is a kilowatt and a half....

You could try a couple of snap on ferrite chokes to limit the high frequency energy making it's way into the speaker wire. Get a couple of these and put them on the speaker wire, close to the speaker.

RF interference can be really tough to figure out. For example, it could be radiating onto the speaker wires, or getting into your power lines and coming in that way on the AC mains. Either way, those ferrites are pretty inexpensive so get a few and try some different filtering techniques.

 

[Surly73]

If you're hearing a local transmission, you aren't going to hear a "squelch". The sound you refer to is an FM narrowband characteristic at the receiver and wouldn't happen from simple RFI due to a nearby ham. The characteristic squelch sound isn't part of the transmission.

It's possible that someone is running a repeater from nearby your location, which would be retransmitting the squelch tail heard by its receiver, but then you'd be hearing both sides of the conversation.

Legal power output limits are very high for hams although most high-power hams would be in the lower frequencies which operate AM and SSB for voice - no squelch. You should also be able to see a large dipole or beam antenna in your area if you've got a high power ham operating on HF.

Look around your area for ham license plates in the driveway, or antennas on structures. Hams aren't supposed to interfere with neighbours and should be friendly about it. Other than only hearing one side of the conversation, it could be a nearby fixed or mobile repeater. Some police forces have mobile repeaters in their cars to extend the range of portable units - any cops live nearby? Those kinds of things are done more for state/provincial police covering larger geographical areas.

As I think about this, the characteristic of quiet, but clear, voice interference I've often found to be AM. That's back to the possibility of a ham on HF (usually large, obvious antennas, but it could be hidden in an attic) or aircraft. Do you live near an airport? I've usually found FM RFI to be far less intelligible, barely recognizable as a voice. AM and derivatives like SSB don't exhibit squelch tails at the receiver, and typically are not used with repeaters.

 

[Proneax]

Maybe it wasn't a "squelch" per say but some static, mostly after and maybe before each time I heard the voice.

I suspect the people across the street from me, I'll look for an antenna.

In the fall, there was a car that would pull up to their house regularly that had a large antenna mounted on the trunk, and it would come out of our living room speakers VERY LOUDLY. In fact, it was so loud we didn't know it was a voice at first, and couldn't even be sure it was coming from the speakers, it was actually painful to be in the room. Then one time it was a bit quieter, and we could hear someone say "I just pulled up outside" and we looked out and there was the car. Again, we would only hear one side of the conversation.

I live somewhat close to the airport, about 8 miles or so, and we get some planes overhead, but this was too sustained, same voice.

The living room is at the front of the apartment about 8ft from the road, neighbor's apartment is just across the street same distance from the street. We have surround speakers that have about 15feet of unshielded speaker wire running to them along the ceiling.

My bedroom with computer speakers is in the back of the apartment probably 40 feet from the front. I have unsheilded wire running to my speakers from the sub/amp in the middle below. Speakers are about 5 feet apart.

I'm moving out of this apartment in a 2 months so I'm not really worried about fixing it at this point.

Also, the fact that my RF mouse stops working seems to indicate that it is NOT from the mains power. RF mouse just has a little antenna in the base, few cm at most, and from the specs appears to operate @ 27MHz. Is it possible to put a filter on the antenna somehow that wouldn't block 27Mhz? In fact, I've noticed what seemed like RF interference with the mouse receiver before, maybe a bad design.

 

[longblock454]

No joke, my Grandma's washing machine would pick up AM radio stations on occasion!

I am a HAM radio operator. It is required to repeat your call sign every 10 minutes, you might be able to catch that then pull his address from arrl.org. He will likely have no problem helping you determine where or if he is the cause.

 

[guney]

I'm by no means a ham/CB expert but I had dabbled in it a few years back enough to pick up some of the technicalities.

It sounds to me like, no matter how high the limit of legal ham transmission power is, it should not be high enough to allow it to bleed into another frequency band. Since the poster is writing that the transmission interferes with the operation of an RF mouse, and the frequency band of the mouse couldn't possibly be overlapping a legal ham frequency band, the source of the signal must either be using an illegal frequency wildly out of the allowed ham band (not likely) or transmitting at such a power that it bleeds into another band strongly enough to impede the operation of devices using that band.

 

[Surly73]

guney: 27MHz is right in the middle of the old CB band (it could be an illegal high power CB operator - I would expect these to be pretty rare these days) and is adjacent to a couple of HF ham bands (closest to the 10m band). I'm shocked a wireless mouse is running 27MHz, frankly.

Typically RFI into consumer devices is the fault of the consumer devices. The transmitting station can be completely legal but the consumer device is overwhelmed and can be desensitized, receive harmonics, IF images, or simply have voltage induced into conductors and malfunction (motion sensors are very succeptible to RFI)

It's not RFI, but lots of crappy kids RC cars operate in the CB band too. In the old days you could see some kids playing with one, and probably find the signaling on CB channel 22. Key up and make so "oooh ahhh" noises and watch the toy car zoom away into the distance with kids running after it... Not that I would ever do such a thing.

 

[guney]

guney: 27MHz is right in the middle of the old CB band (it could be an illegal high power CB operator - I would expect these to be pretty rare these days) and is adjacent to a couple of HF ham bands (closest to the 10m band). I'm shocked a wireless mouse is running 27MHz, frankly.

I see.

I was reasoning under the assumption that, wherever the frequency band of the mouse might be, as long as it's FCC approved (which it probably must be), it should spaced far enough from any other adjacent frequencies that nothing should interfere with anything else as long as everyone is within legal transmission power limits and on valid frequencies. But then, I'm not that familiar with what actually goes on in a typical scenario.

Looking around for a couple of minutes on Google, I can see that some wireless mice do operate around 27MHz. Not sure why. (I wonder if they're supposed to be above CB channel 40. As far as I see, channel 40 is at 27.405 MHz. There's still about 0.6 MHz of bandwidth there that could be called "27 MHz" that's outside of the CB channel range...) But, there are some others that use different frequencies too. I'm not sure which is more common. Though, this is very likely to be a case of a 27 MHz given the posters account.

In the old days you could see some kids playing with one, and probably find the signaling on CB channel 22. Key up and make so "oooh ahhh" noises and watch the toy car zoom away into the distance with kids running after it... Not that I would ever do such a thing.

That's pretty funny! I like that.