Thanks for the interesting reply Lyle, I am mostly interested in operating on HF. QRM is not such an issue on HF as the signal to noise is so much worse. I know what you mean about minimizing the gain before the selectivity but at VHF one has a low noise floor to work with so that does not really work. You need a low MDS.
I operate with the XV144 and with the pre-amp off and with a 15 dB attenuator in the 28MHz IF. This does nothing good for the noise figure of course but I have a switchable pre-amp at the front to deal with that if needed. The XV144 has a bit too much gain for my situation and I am looking forward to the internal 144MHz option arriving on my doorstep next month. I don't think the limit is the hardware AGC - I thought it was the DSP one responding to the very high signal energy within the filter bandwidth but outside the main passband. I agree a tighter filter would help. I would like a variable crystal filter please! I am prepared to build my own if the K3 can be made to tune it. The K3 deals with this situation very much better than anything else, especially now I have fixed the VCO spurii problem. It is a monthly inter-club sprint contest and I have 2 other stations within a mile and line of sight. In the interim, I am thinking of perhaps using a second antenna and seeing if I can do this nulling at RF. Mike -- View this message in context: http://n2.nabble.com/Nulling-QRM-tp3572519p3573374.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
