I live about five miles from the WYAY tower in Loganville and was wondering why the station comes in through my computer speakers. This started recently. Does this have anything to do with the recent FCC authorization to increase the power on HD radio stations?
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True Oldies 106.7 is coming through my computer speakers!
- Thread starter RadioDoogie
- Start date
Sounds like an RF problem. You may need to shield your speakers. For more on that "Google". I had a ham radio operator on a set of speakers I was using. I replaced the speakers and the problem disappeared. Years ago, I had a friend who lived near the transmitter farm of a 50 kw AM station. He received the station on his land line, TV set and sometimes even his water pipes!
This is NOT a common situation with FM stations, because it's not as easy for an unintentional detector circuit to develop that will decode
frequency deviation into audio. It seems there is enough signal "just walking into" the speaker circuit and decoding.
This is much more common with strong AM signals.
Does the volume control have any effect, or is it constant volume? Does moving the wiring change anything?
What happens when you unplug them?
Do these plug into the headphone jack, or are they USB speakers?
Upping the HD power would only make the whine, or "buzz saw" noise portion of the signal louder, but not change the "old-fashioned"
frequency deviation of the analog portion.
frequency deviation into audio. It seems there is enough signal "just walking into" the speaker circuit and decoding.
This is much more common with strong AM signals.
Does the volume control have any effect, or is it constant volume? Does moving the wiring change anything?
What happens when you unplug them?
Do these plug into the headphone jack, or are they USB speakers?
Upping the HD power would only make the whine, or "buzz saw" noise portion of the signal louder, but not change the "old-fashioned"
frequency deviation of the analog portion.
You also may be able to move your speakers around your desk and make it go away.
fussbudget said:
That's pretty cool!
Back in the early to mid-90s, our TV use to pick up CB Radios or some other type of radio communication (non-FM or AM) on "cable" channel 19 (which at that time, was USA.)
I remember hearing that people near the Chateau Elan tower had this problem with Fox 97, but only on other FM receivers (TVs, radios, and I would guess other FM devices like baby monitors).
I still have a problem with WCNN 680 bleeding all over the AM dial (even WSB!) under the high tension lines that parallel Pleasant Hill/State Bridge Road. I'm guessing that that part of the electrical grid is electrically "close" to the WCNN transmitter off Spalding.
I still have a problem with WCNN 680 bleeding all over the AM dial (even WSB!) under the high tension lines that parallel Pleasant Hill/State Bridge Road. I'm guessing that that part of the electrical grid is electrically "close" to the WCNN transmitter off Spalding.
A lot of filters were given away when WFOX and WYAY were colocated.
I suspect the current problem with WYAY is a lack of warm bodies, brought on by a lack of loot. Where there are multiple FMs on one antenna, a shift in tuning or in the antenna itself can lead to strange and marvelous stuff. If the filters aren't compensated for temperature change, for instance, the combiner can get a little wonky in weather extremes.
I note that the WYAY audio feed has a recurrent audio drop every thirty minutes or so... I'd bet a small amount of money that the digital line is reframing due to a timing error someplace in the telco, having had it happen to me. Again, it takes someone to babysit it and bitch loudly till they repair or replace the broken equipment. If most of the circuits your audio bitstream is riding are regular telephone cuircuits, no one will complain about the occasional click or pop. And if you haven't the manpower to have someone spend the time it takes to stay on the telco, you learn to live with the repetitive dropout.
I suspect the current problem with WYAY is a lack of warm bodies, brought on by a lack of loot. Where there are multiple FMs on one antenna, a shift in tuning or in the antenna itself can lead to strange and marvelous stuff. If the filters aren't compensated for temperature change, for instance, the combiner can get a little wonky in weather extremes.
I note that the WYAY audio feed has a recurrent audio drop every thirty minutes or so... I'd bet a small amount of money that the digital line is reframing due to a timing error someplace in the telco, having had it happen to me. Again, it takes someone to babysit it and bitch loudly till they repair or replace the broken equipment. If most of the circuits your audio bitstream is riding are regular telephone cuircuits, no one will complain about the occasional click or pop. And if you haven't the manpower to have someone spend the time it takes to stay on the telco, you learn to live with the repetitive dropout.
Tom Wells said:
Uncommon, but it does happen. We had some trouble with it at my workplace. (a TV station, but we lease space on our tower to a 100,000-watt FM station)
Things I would try to fix it:
- Try to bunch up the cables connecting the speakers to the computer and to the power supply.
- Try relocating the speakers.
- Try a set of "choke cores". At least at one time, Radio Shack sold these - I hope they still do. They're O-shaped plastic things with a ferrite insert. You wrap the connecting cables around the cores as many times as possible. Use one core on each cable (you get two in a package) and place them as close to the speakers as possible.
Computer speakers are VERY VERY VERY poorly shielded/filtered, they're EXTREMELY susceptible to this kind of thing...
Lengthy technical explanation follows:
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Imagine that you have an FM broadcast signal on 95.5MHz, swinging +/- 0.075MHz with the program audio. And imagine you have a selective circuit, that passes 100% of any energy it receives at 95.425MHz, 75% of what it receives at 95.500, and 50% of what it receives at 95.575.
As the station's frequency swings between 95.425 and 95.575 with the program audio, the amount of signal passed through the selective circuit swings between 50% and 100%. Voila!, you've converted frequency modulation to amplitude modulation.
The process is called "slope detection", and has been occasionally used by hobbyists to receive FM communications signals on receivers not designed to receive FM.
It could be what's happening here.
It could be happening in the speakers -- there is some kind of resonance either in the speakers, or in the wiring connecting them to the computer, so that it's picking up the FM signal with an efficiency that varies with the precise frequency.
More likely, it's probably happening at the station. Something in the transmitter's tuning is set to too narrow a bandwidth, and the amount of power actually being transmitted is varying with frequency. Your speakers are picking up the RF and decoding the inadvertent amplitude modulation. (this modulation would reduce the station's coverage -- by effectively reducing power -- but the reduction is so slight I doubt any listeners would notice.) (a small mount of inadvertent amplitude modulation is legal for FM stations. I want to say 3% but don't hold me to that figure.)
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Or, suppose you have a very stron RF field at 106.7 and at 104.1. Suppose further that the computer speakers aren't the most linear devices ever made. Now, it is easly possible to get a very strong difference frequency inside the speaker amplifier itself, which is easily detected in the amplifier - particularly if the difference frequency is strong enough to drive any stage of the speaker amplifier pour of its linear range. Note that no action taken by either of the stations save turning one off is going to correct the problem. It arises in the speakers themselves. That being said, W9's suggested solutions are the fix, if in fact it can be fixed.
notalkallstatic said:
Analog cable channels 14-64 coincide with spectrum assigned to other-than-TV services. For example, the lower 2/3 of analog cable channel 18 is the 144-148MHz ham radio band. Cable 19 is 150-156MHz; this spectrum is (or at least was in the early 1990s!) full of both commercial and local-government two-way radio services.
Most of channels 23-64 is spectrum assigned for military communications. However, 60-64 are another band of commercial and local-government two-way services.
In both cases the "interfering" signals are in fact the legal occupants of the spectrum. Cable TV is allowed to use the spectrum on the condition it doesn't interfere with the legal occupants and accepts any interference it may receive from them.
littlejohn said:
Not that it affects the fix to the problem, but this is not technically correct.
You're talking about intermodulation. Strong signals on 106.7 and 104.1 appear in the same non-linear circuit; they get mixed, and you get four outputs:
106.7
104.1
106.7+104.1 = 210.8
106.7-104.1 = 2.6
If your speakers respond to any of these four frequencies, they'll receive interference.
But the intermod doesn't convert the frequency modulation to amplitude modulation. The intermod interference would cause a shift in the DC operating point of the speakers -- it would reduce the volume you could accomplish without distortion and in severe cases, the speakers could go silent altogether -- but it wouldn't cause you to actually hear the stations' audio.
Something else must be converting the stations' FM audio to AM.
(it is REMOTELY possible an "inadvertent selective circuit" in the speakers responds only to 2.6MHz or 210.8MHz, so that only through intermodulation is it possible for this "slope detection" to happen. But you'd hear a mix of both stations' audio, not just 106.7.)
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This intermod can cause other interference problems though. For example, in the above case the 210.8MHz signal falls within TV channel 13. If you had an antenna TV near the speakers, this intermodulation happening in the speakers could interfere with reception of the channel 13 station out of Macon.
Yeah, .7, not .1. I get them mixed up. And if the system is non-linear it will by definition produce an AM component, since it does not reapond linearly. But we're off to picking nits here. Point is, enough RF into a cheap amplifier will often let you listen to the radio when you don't want to.
Many moons ago, I ran camera for ch.13 in Birmingham, which sat right under its tower on top of a mountain loaded with iron ore. I would enjoy listening to its FM station over my headset when I parked the camera in a certain place in the studio. Also, legend has it that its AM radio studio in the building was the most expensive in the world because it had to be literally wrapped in copper.
And, I believe some merchants in the shopping center around WSB's tower have some stories to tell...
Many many moons ago, I met a guy who said WGUN came in through his hot water heater. Maybe I met your friend.
And, I believe some merchants in the shopping center around WSB's tower have some stories to tell...
I don't think that's correct because everything electrical in the stores is tied in to the WSB ground system. The stores are not allowed to do anything without involving WSB's engineers.
Now...if you said some nearby residents have some stories, you'd probably be right. I live about 6 blocks away and have gotten WSB on more than just my radio.
My parents used to live a stone's throw away from a 3 tower AM radio station. All you had to do to listen to the radio station was pick up the phone. Later, when I got into the business, and I heard the line about "W### is listened to on more radio's than any other appliance" I would always think about picking up that radio station on the telephones.
jabba17 said:
You were probably receiving some sort of intermod created when the sections of the combiner contracted due to extreme cold.
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