odd signal/interferance question

[Kaligus]

details at http://xmission.com/~wblalok/radio/mystery0001.html

The quick and dirty version, two radios, several antennas, same "signal" from about 250Mhz to about 300Mhz, started after 2 hours of listening for activity on 277.3Mhz (I.E. not scanning) and continues 4-1/2 hours later. I have not heard this before, and have been playing in the AM Mil-air bands for about 2 days now.

If I squelch the radios I hear what sounds like keying and releasing a mic at 2.5 second intervals, if I un-squelch the radios I hear a longer burst each time. Visually recorded the blips at almost exactly 2.55 seconds apart over half an hour (the link above is to a 15 second or so clip and all pictures I know how to generate that are any good for solving audio/radio mysteries)

I walked about a 1/2 mile from the house in 3 directions same strangeness. I don't know if location helps any but 40.69N 111.93W is close enough for government work.

Any ideas on what this is and/or how to eliminate it before it finishes the trip to "mad" with me?

 

[nexus]

The only two guesses I could come up with would either be a military satellite, or perhaps a radar station? I know the band you're in is usually where all of the satellites are.

 

[fineshot1]

Possibly cable tv leakage. Have you checked for the video carrier buzz and the audio carriers for any of the cable tv channels?

 

[w4esp]

interferance 250 mhz

do u have another scanner or electronic device running near by, could be getting mixed signal from an other receiver or time base signal from a cpu ? good luck, let us know what u find

73

tom w4esp

 

[kb2vxa]

Hi Kaligus and all,

Considering you're a spit from Salt Lake City Intl. Airport my guess is radar of some sort but it doesn't have the characteristic fade in fade out buzz of the circular sweep. Unfortunately you didn't have the input level set correctly when you recorded it, the background hiss is normal but the burst is clipped being you took no notice of the peak value. Here is an oscillogram of the expanded burst, clipped as you can see so there's no way of knowing it's waveform but take note of the spacing. It's not a single frequency, >looks< like pulse width modulation (PWM or PDM if you prefer) but I can't say just what it may be since it's clipped off and distorted.