Topband: BCI

Gary Smith Gary at
Mon Mar 3 21:21:56 EST 2014

I've been plagued by a problem I have finally identified but now need 
help in resolving. I thought it was birdies but realized it had an 
external component when I removed my antennas and they went away. 

I'm in a location where I can't put up a tower but have made 
extensive use of wires in trees and use my 160M Inv-L for 160, 20, 
15, 12 & 10 meters. the 80M mostly vertical wire also serves for 80, 
17, and 12 meters. 

I have been hearing birdies on 18 meters for a long time but recently 
I bought a P3 to fit the K3 and now can see much more than my alone 
ears noticed before. I only used CW and never listened to the signals 
and only bypassed them. When I had the 160M ant in line & switched to 
18M, I saw lines 5KHz apart on the P3. Usually I only have the 80M 
antenna in-line on 17M so this was a real discovery for me. Seeing 
that the interference was audio I listenbed on AM & could hear audio 
which using the 80M ant & narrow CW filters, I never had before. With 
the 160M antenna what used to be an irritation was now overwhelming 
interference to reception. And what I thought were birdies were the 
centers of the carrier on regularly spaced narrow AM signals 
generated in the circuitry.

One station was an AM station from Puerto Rico and the other I never 
did listen long enough to, to hear the call but was stateside. 
Switching in the 80M antenna makes the lines on the P3 far less 
aggressive and switching to a 30M vertical, I see no lines 

I took two waterfall screenshots from the P3 and birdie1.jpg is 
showing 11KHz on each side of center and birdie2.jpg shows 100KHz on 
each side of center. Each line is 5 KHz.

These are the worst on the transmit antenna but also am hearing them 
to a lesser extent on the HI-Z Triangular antennas as well.

It seems like I should have a filter in line to block the BCB signals 
but then that would block 160 signals as well. I use the HI-Z for 
lowband work and certainly don't want to block those signals & the 
same goes if I put a filter in the coax for my transmit antenna.

Any suggestions of some kind of filter so I can get rid of these?


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