Topband: The Forbidden Frequency

[Charles Bibb]

Hello, fellow Topbanders:

Maybe this has been covered here before, but what's up with the QRM (steady 
carrier) on or about 1830khz?

Almost everyone across the country regards 1830 as a "bad" frequency and 
avoids it, but where does the signal come from?  I've read many DX spot 
posts that call it BCI, but is it really? 1830khz would be the second 
harmonic of 915khz, but MF AM stations in this country are spaced at 10khz 
intervals. 1830khz is also the third harmonic of 610khz. There's not an AM 
station operating on 610khz anywhere near me, so for so many op's in all 
parts of the US to hear the same signal, there would have to be mis-tuned 
610khz transmitters everywhere. And, if it's BCI the source would have to 
be located close by beacuse I hear it 24/7, not just during the hours of 
darkness.

Actually the closest I can zero-beat the signal puts it at 1830.24 plus or 
minus a few hertz. Also, it varies in signal strength depending on which 
antenna I'm listening on. It's moderately loud on the vertical TX antenna, 
very weak on the 800' NE terminated beverage, and very bothersome on the 
550' E/W bi-directional un-terminated beverage.

The only broadcast transmitters operating near me (about 1.5 miles to the 
ENE) are all VHF or UHF:  FM at 90.9Mhz, TV CH2, TV CH23, and FM WX radio 
on 162 point something. The nearest AM station is 10 miles to the NNW and 
only 1000W in power. Could it be a harmonic or sub-harmonic of some 
modulation process generated by and common to all TV and/or FM 
transmitters? (Like the TV color burst carrier on 3579.545khz) Or could it 
be some oscillator signal or artifact coming from within our own transceivers?

Any thoughts?

Charles - K5ZK