I have had this problem off and on (and noticed it with others) for about two years now. It appears that everytime I get near a strong wireless signal there is this loud buzzing noise on the high FM radio frequencies. At first I thought it was power line interference but then I've noticed it in places where the power was entirely underground. Although I suppose RF *could* be emitted and strong enough to go through concrete and disrupt radio signal.
I have heard from a lineman that when power transformers go they start emitting RF at different frequencies. I am not completely ruling out power interference...
I don't know much about harmonic frequencies but I seem to recall from school something about harmonic distortion. Something to the effect of if 2.4ghz is divisible down to 107.7-9 that there could be interference. Although I won't stake anything on this theory.
One possibility of what you're hearing are the harmonics of the clock oscillator that runs the access point, or the clock oscillators that run the computah to which the wireless device is connected. You'll have similar interference, although at different frequencies, with a fax machine, digital clock, calculator, or any device that has a clock oscillator.
Another possibility is entry directly into the audio circuitry. You noted that it's from 107.7 to 107.9MHz, so this is probably NOT what you're hearing, but does happen (to my cheapo hi-fi). The audio amplifiers have very little RF bypassing and will respond to almost any nearby RF signal. The SSID broadcast interval of the typical
802.11b/g access point is 10 times per second. I can hear that on my cheapo hi-fi as a raspy buzz. Moving the access point away solved that problem.
If you change the DTIM interval (or data beacon rate) on your access point and the rate of the loud buzz changes, then you're picking up the 2.4Ghz RF directly, or possibly one of the clock frequencies used to generate the 2.4GHz, and not the clock oscillator as I previously guessed. Note that todays 2.4GHz chipsets are all digital (no mixers or local oscillators) which offer plenty of clock signals to radiate.
Wanna disclose what make and model of hardware is causing the problem or is it every wireless device that you bring your radio near?
The RF that the lineman was referring to are harmonics of 60Hz. What happens is that the AC power line waveform is normally fairly low distortion and shows few harmonics. When the transformer core saturates or a turn shorts, the waveform becomes distorted and starts to show harmonics, which can easily extend into the RF region. Mostly, you'll hear it on AM broacast band (1MHz) frequencies. However, I don't think these will extend into the FM broacast band.
Normally, that's the result of arcing - sparks if you wish. This is the mechanism originally used to generate RF in the early part of the _last_ century (think the transmitter on the RMS Titanic). The interference is usually much more noticeable at low (AM broadcast) frequencies than VHF or above, Also the design of FM receivers is such that the effect of impulse or amplitude modulated RF is minimized.
Normally, it's the other way around - the desired stuff is generated at lower frequencies, and multiplied up to the working frequency. Here,
2450/108.8 is about 22.7:1 which isn't a logical number. 20 (4 x 5) or 24 ( 2 x 3 x 2 x 2) are more common multiples.
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