Barry N1EU wrote: Bob, this topic has come up a few times in the past and is something that has my full interest during/after each cw contest. I hate to say it, but I don't think there's much of a solution via AGC settings. I typically run with AGC OFF and minimal RF Gain to try and maximize transfer of RF to AF rx dynamic range, but it honestly doesn't help much with the pileups. Perhaps it's just the nature of K3's A/D/A. I've used both the K3 and Orion in
ARRL160 this weekend and my sense is that the similarly rx gain optimized Orion does a bit better in those situations where there are multiple callers on frequency. 73, Barry N1EU Hello Barry, Comments from others indicate a perception of within passband IMD as the cause of the problem. In response to this I made some measurements this morning. The following measurements relate to K3 S/N 4904 on 7MHz with 2.7kHz roofing filter and 2.7kHz DSP b/w. Default slow AGC was selected. The following table shows input level at the K3 antenna connector for each of two carriers spaced 500Hz. At each input level, the level of the strongest IMD product observed on an HP8568B is recorded alongside. -73dBm Better than -55dBc (Input S9) -63dBm -55dBc -53dBm -50dBc -42dBm -45dBc -33dBm -42dBc -23dBm -37dBc (Input S9+50) These figures are good and IMHO entirely acceptable. Some older transceivers would struggle to provide -35dBc at S9. I made a similar set of measurements with my old K2 S/N 997 -73dBm -50dBc -63dBm -48dBc -53dBm -45dBc -43dBm -48dBc -33dBm -45dBc -23dBm -15dBc Broadly speaking the K3 is as good or better than the K2, which is itself good. It is possible later mods to the K2 may have made it even better. The most recent mods to my K2 were carried out over 5 years ago. These figures appear to confirm within passband IMD is not creating the mud. Perhaps AGC artefacts generated in a more dynamic (true to life) scenario might be the cause. The addition of Bandwidth Adaptive Stereocode to the K3s DSP armoury might provide dramatic benefit. The current AFX facility doesn't seem all that useful. The term Bandwidth Adaptive Stereocode likely won't mean much to many. You will recall Orion offered Stereocode for CW but its effectiveness in narrow b/w was very limited due to the code having been optimised for wider bandwidths. Listening to CW on Orion in an SSB b/w with stereocode enabled provided an impressively wide sound stage which significantly aided signal separation. Unfortunately the fixed b/w code resulted in a sound stage which shrank with reducing b/w similarly reducing its usefulness. In my time between Orion and K3 I have been fortunate enough to become involved in G3XJP's PicaSTAR project. Peter implemented Bandwidth Adaptive Stereocode in Picastar DSP. The results have been dramatic. Preferred pitch appears centre stage with lower tones moving progressively off in one direction and higher in the other. As the bandwidth narrows so tonal separation increases across the sound stage. I'm not aware of any commercially produced Ham transceiver which offers this capability. Perhaps Elecraft will be the first. What say Lyle? 73 Bob, 5B4AGN ______________________________________________________________ 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
