Many thanks to all those who responded to my mail. I was trying to find from those who were using the K2 VOX, their experiences, and see if they were similar to mine. Without referring to individual mails the comments fell into these main categories.
a) Use CW, don't use SSB, so don't use any VOX ! b) Don't like VOX on any rig, preferring PTT operation. c) Use VOX sometimes, but prefer to the control of PTT. d) Mode control to select VOX clumsy. e) VOX OK when using headset. f) Background noises trigger VOX e.g Phones, Jets, Kids, Mother in Law etc. g) VOX cuts off the first syllable of words. h) Low VOX sensitivity. i) No VOX gain adjustment. j) Lack of Anti-VOX. I think that's covered most, but if I have missed your input please let me know. Comparing the list with my experiences I found that I agree with most points. I do not operate CW, and would like to use the VOX on the K2 more frequently. In my experience the KSB2 board has the following deficiencies in the audio path:- 1) Low input sensitivity. For some low output microphones there is insufficient audio input to the speech compressor U3 leading to a low RF output, and poor VOX operation. This sometimes results in the first syllable of a word being lost. External pre-amps may help, but this can lead to other VOX problems. 2) The VOX detection is derived from the speech compressor. Although in principle this seems like a good idea, however, it means that ANY signal from the microphone that is strong enough to activate the compression threshold will trigger the VOX. So the K2 VOX is very susceptible to background noises. Most other rigs take the processed speech and VOX trigger signals through separate paths. That way you can have a good amount of speech processing and still get reliable VOX operation. 3) Lack of individual adjustment of microphone and VOX gain. The two adjustments should be independent for the above reasons. 4) Lack of Anti-VOX. This to me is a real pain. It has put me off using the K2 VOX more than anything else. I'm surprised that this did not get more mentions in the mail. It really fired me into sending the original mail. Enough moaning !!! To cut to the chase. I have spent some time thinking about the KSB2 problems and after much design work using a circuit simulator have come up with a solution to address items 1-4. This solution is at a breadboard stage at present (sitting next to my K2/100), and is working very well. Although it is far from complete I can give some brief details, so you might care to comment. It will be a PCB that sits above the audio section of the KSB2, connecting via approx 6 short wires to the KSB2 PCB. It will require 1 track cut and 1 component to be removed from the KSB2 PCB. It will have the following:- a) An integral tailored microphone pre-amp with Mic gain adjustable from 0 to +20dB. The input impedance will be 500 ohms. b) An independently adjustable VOX gain control, driven from the microphone, and NOT the speech compressor output. c) A fully adjustable Anti-VOX function that is derived from the speaker output. As I said there is still some work to be done, but I will keep the group informed of my progress. 73 Stewart G3RXQ _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
