Re: K3 Beta firmware rev. 2.82

Posted by Julian, G4ILO on Feb 15, 2009; 11:14am
URL: http://elecraft.85.s1.nabble.com/K3-Beta-firmware-rev-2-80-Improvements-to-AFSK-A-DATA-A-SSB-AM-FM-DVR-tp2305650p2329434.html

I have just run a set of tests across a range of audio frequencies as did Joe, KB8AP. The results were almost identical, so I am not going to tabulate them here. In SSB I adjusted the input level to give sufficient drive and just enough ALC action to result in a flat output from 600Hz to 2600Hz.

At the same time I checked the PSK31 IMD level across the spectrum using the KK7UQ IMD meter. I observed no degradation of IMD resulting from the use of minimum ALC to control the power to a flat level, compared to using DATA A mode where there is apparently no ALC feedback at all. Therefore it seems to me that the solution that has apparently been adopted in DATA A mode for the purpose of minimizing IMD is in fact producing no useful benefit at all, while at the same time depriving data users of a meaningful power control.

I would much prefer the K3 to work the way other radios work, where you can increase the drive level until the ALC just starts, and then you know that you are producing the requested power and no more. This is how I believe it used to work in early versions of the firmware. DATA was just USB with a different input source option and compression automatically disabled.

I will concede that the approach adopted by Elecraft is more foolproof in regard to avoiding IMD, but this is achieved at the cost of a loss of confidence in knowing the output power. However for me it is just too unsettling to not know how much power the radio is putting out, particularly as I wish to operate remotely via the network and can't see for myself the power output. I have had to give this up for the last few months after I found myself transmitting nearly 100W when I was intending to use 40W.

If the majority of other data mode users are happy with the K3 the way it is and Elecraft can't or won't change it, then it's probably time for me to look for another radio.