GM4JJJ wrote > I find that I can get an annoying weak heterodyne that is too weak for > the auto notch to find, and if I could tune the notch manually I would be > able to notch it out.
I was thinking perhaps for the weak heterodyne issue, you could use the RX EQ feature. It is a broad brush, but it does have +/- 16dB of range in 8 bands. I tried that and found something rather interesting. The RX EQ is applied *before* the AGC! I never knew that - maybe I'm the only one. Makes sense since the IF is 0Hz - why waste AGC on energy I don't want. Kudos to the Elecraft engineers that thought that though the extra step! The auto-notch feature is great for intermittent tuneups or other (multiple) CW signals in the SSB passband, but it is applied after the AGC. That works well if interferer is equal to or less than the level of the SOI (signal of interest), but for the case where the interferer is much stronger than the SOI, the AGC is dominated by the RFI and can make the SOI difficult to copy. At least the tone is not blasting away in my ear;) But it does present a problem. There is a work-around. Use CW mode to receive the SSB signal, and harness the power of the manual notch. If in a QSO, use split mode to operate SSB on transmit and CW mode on receive with the filters widened and pitch offset removed to receive the SSB signal. Don't forget to turn off split when your done! =:O. I put the KX3 on the bench and measured the CW notch depth using the built-in dBV meter. I measured more than 60dB! If I adjusted the VFO about +10Hz, it was over 90dB!!! How accurate is 90dB?? Well, call it +/-10dB and you still get 80dB min! That is a *considerable* RFI countermeasure. And the best part? It is before the AGC!!! As an experiment, I tuned to 7255KHz where ECARS is active and used a siggen to create a CW RFI in the middle of the passband at S9+20dB. The auto-notch completely removed the tone, but I could not copy the net - S meter still at S9+20dB. Switch to CW mode and adjust for SSB receive. I could completely remove the CW RFI with the manual notch - gone! And the AGC was now totally operating on the signals - noise level was S2, signals were as low as S3. I suppose technically the AGC was noise driven at S2, but that is the point - no RFI. Note: for LSB use CW, for USB, use CWR. This is a really cool thing. I have, on occasion, had the problem of the "antenna matching enthusiast" coming up in the middle of a QSO, and making things challenging...for several minutes. I guess they are going for that last decimal point - and have no need for RX mode:\. Using CW mode and the CW notch in this situation makes it very easy to apply rule #1: Don't acknowledge the presence of the interferer - because they are no longer there! This is especially useful if the RFI is not an "antenna matching enthusiast", and does have RX mode :(. Happy Holidays! 73, Steve WD4SDC -- View this message in context: http://elecraft.365791.n2.nabble.com/KX3-Notch-Filter-Was-Noise-Blanker-Comments-tp7611375p7611849.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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
