The sidetone mod by TF3MA was installed in my K2 right after Marti posted it. I obtained a 47 mh inductor for this mod from Elecraft. The mod resulted in an improved sidetone, but left room for further improvement, especially at lower tones. Additionally there was an objectionable pin-prick sound at the make of the muting that was annoying to hear.
Recently I decided to revisit this situation. I noticed in Marti's write-up that HIS 47 mh inductor had an internal resistance of 180 ohms. With the K2 apart, I measured the inductor I had received from Elecraft and sure enough, it had an internal resistance of only 40 ohms. This would entirely change the frequency response Marti's peaking high-pass filter. Elecraft is apparently using an 82 mh inductor in its mod, I obtained that, and found it has an internal resistance of 60 ohms which would seem to offer less than an ideal result. I put a 150 ohm resistor in series with the 47 mh / 40 ohm inductor originally used when I modified the radio some years ago. Folks, the difference is DRAMATIC !!! The sidetone is louder, clear, and is that way across its entire range from 400 to 800 cycles. Not only that, the tone is so much stronger that the slight pin-prick click from the make of the muting line is all but completely inaudible in the strength of the sidetone and no longer objectionable. A big thank you to Marti and to W3FPR who both stayed with me through my frustration trying to make this thing right. For a while they must have thought my hearing was the main problem because the radio seemed to have the right modifications in it to sound well. Maybe this will be helpful information for others. 73, Fred KT5X _______________________________________________ Elecraft mailing list Post to: [email protected] 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
