The loop I built decades ago is made from 2 turns of 1" CATV hardline of 40" diameter which is remotely tuned by a set of BCB diodes and feeds PP U-310 Fets. There has never been a problem of BCB or any other intermod even when doing BCB DXing.
Some loops have such poor Q that they are wide open to interference problems. The hardline I chose has the lowest C per foot and therefore the highest Q with the resultant narrow bandwidth and need to retune for even a small QSY. The preamp is very helpful and is not run at high gain, just enough to give a comfortable signal level. Preamps can be unstable at any frequency and need attention to layout detail, bypassing, properly sized inductors, etc. Carl KM1H ----- Original Message ----- From: "Guy Olinger K2AV" <[email protected]> To: "rick darwicki" <[email protected]> Cc: <[email protected]> Sent: Wednesday, September 14, 2011 7:20 PM Subject: Re: Topband: BCB interference on 160 > The problem would be that you need to trap out the BC signals BEFORE they > reach the tuning diodes. In the good ole days with signals that were no > more powerful than now, a small antenna, a coil, capacitor, and a diode > would produce enough rectified audio to drive a pair of headsets WITHOUT > any > amplification whatsoever. So there is plenty of RF to intermodulate two BC > signals on a tuning diode, even if the IM is 60 or 70 dB down. 73, Guy. > > On Tue, Sep 13, 2011 at 10:42 PM, rick darwicki <[email protected]> wrote: > >> Hi all, >> >> I recently built a sheilded RX loop for 160 per N6RKs Contest Jouranal >> artical. It is diode tuned and covers about 1.5-4 mhz. I am hearing two >> AM >> radio stations on 1830 khz. >> They are 640 and 1190 combined. 640 is a 50KW station about 12 miles east >> and 1190 runs about 1.5 kw at night. >> >> The anetnna is all sealed up and on the roof. I would like to cure the >> problem without changing to back to back tuning diodes. >> >> I'm thinking a series trap tuned to 1190 or 640 or both. Maybe a high >> pass >> filter. >> >> Any suggestions? I can built it, I don't want to spent $200 for the W3s >> highpass hi hi >> >> >> Thanks, >> >> Rick, N6PE >> >> ============================================================================= >> If I agreed with you we'd both be wrong. >> _______________________________________________ >> UR RST IS ... ... ..9 QSB QSB - hw? BK >> > _______________________________________________ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > ----- > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1410 / Virus Database: 1520/3898 - Release Date: 09/15/11 > _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
