Bottom posted for context. Geoff GM4ESD wrote
"If I had a K3, before I changed the HAGC threshold my *first* measurement would be to look at the output of the SA612 mixer (with a spectrum analyser) while introducing two or more very close spaced signals into the antenna port, so that these signals do get through the roofer - as in a pileup. The objective, of course, would be to obtain an acceptably clean output from the mixer with non intrusive products over a wide range of input levels. IMHO the higher the HAGC's threshold can be the better, provided its control is tight enough when activated to protect all what follows." I made within DSP b/w IMD measurements on my K3 and comparable measurements on my K2. These were included in a post dated 5 December but you may have missed it. 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 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 at the AF output using 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. 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
