It is unusual for AM BCB signals on a 10 khz raster to produce signals every 5 khz.
It is relatively simple to insert a MW rejection filter in a RX ant loop which should alleviate or cure the problem without having it affect 160m signals. For example: http://www.cliftonlaboratories.com/z10020_am_medium_wave_band_reject_filter.htm or https://arraysolutions.com/Products/bcb_filters_top1.htm Filters that you can transmit thru are also available such as: https://arraysolutions.com/Products/BCB%20RF%20Filters.htm 73 Don VE6JY On Tue, Mar 4, 2014 at 2:21 AM, Gary Smith <[email protected]> wrote: > 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 > whatsoever. > > 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. > > http://doctorgary.net/birdie1.jpg > http://doctorgary.net/birdie2.jpg > > 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? > > Gary > KA1J > > --- > This email is free from viruses and malware because avast! Antivirus > protection is active. > http://www.avast.com > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband > _________________ Topband Reflector Archives - http://www.contesting.com/_topband
