Pat, I cannot find the schematic of the HF Packer amp to verify this, but my suspicion is that the input impedance of the amp might be changing with the level of drive signal. This change will occur rapidly of course in the case of SSB.
If this is the case then distortion could result either because the driver (the K2) cannot handle a rapidly changing load impedance, or there is something amiss in the amp's feedback network which causes the amp's input impedance to change with drive level - but my inclination is to suspect the former. One clue is the occasional turning off of the amp's rf sensing T-R switch when the driver is a K2, but not when the IC-703 is the driver. This suggests that the K2 is not happy with a rapidly changing load impedance, which in turn suggests that the distortion is generated by the K2 not the amp. You could try reducing the drive level from the K2 to see if the distortion disappears at some point. Your idea to place a resistive pad between the K2 and the amp could well cure the problem. The reason why the K2's ATU did not cure the problem is most likely that the ATU cannot switch fast enough to keep up with the rapidly changing load presented by the amp. Good luck. 73, Geoff GM4ESD Pat Byers wrote on Tuesday, September 14, 2010 at 03:08 +0100 >A friend recently dropped off his K2 and HF Packer amp for me to > troubleshoot a problem -- he was getting poor quality SSB reports on > the air when he ran his K2 through his HF Packer amp. I had built > both kits and had tested them separately so I was a bit skeptical > that there was anything wrong. :-D However, when I ran the K2/HF > Packer combo into a dummy load and monitored the transmitted signal > with my Icom IC-703 I confirmed that the transmitted signal was > significantly distorted. Hmmm . . . What's wrong? <snip> ______________________________________________________________ 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
