Glad to hear it’s not just me who finds this a bit slow for QRQ CW. If you send up to about 20wpm, you may not really notice anything. MTR3b a clear winner on this point. I think the SW3B wins out on most of the others.
73 de Matt
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There is a solution for recent SW-3B rigs that have a long T/R switching time. On my rig, bought Feb. 2024, the T/R switching time was 600 ms. It was long enough that I missed the first few characters in callsigns coming back to me. Judging from videos of earlier SW-3B prior to 2022, the T/R used to be near-QSK.
The value of a capacitor C37 on the RC network applied to the MUTE signal going into the receive section is too high. The schematic says 0.01 uF, but I measured mine as 0.1 uF. This would apply an extra long time constant on the switching. When I replaced my C37 with a 0.01 uF cap, my T/R went down to near-QSK.
This part of the schematic is similar to the Elecraft KX1, where the cap in the RC network is also 0.01 uF. Now my SW-3B and KX1 have similarly short T/R switching times.
The cap is easily accessed on the bottom of the board and is a fairly easy job. It made this rig an even better one, combined with the recent improvements on CQ memory flexibility and screen visibility.
73 Mike N9OHW
Edit: added photo of the bottom of my board where I changed C37, the SW-3B schematic from Venus’s website, and the KX1 schematic from Elecraft’s website, both showing 0.01 uF for this capacitor.
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Really a very helpful tip, thank you very much for sharing, Mike!
I just made the modification (with a very small, bent, leaded 0.01 uF capacitor …), it works as promised and frees my previously unused SW-3B2c from its useless existence in a closet, hi.
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That’s great to hear. It’s otherwise a great little rig. I also tried without the cap and that also works, but there may be too little filtering then. I could hear a small “pop” after each element. I may experiment with values lower than 0.01 uF to see how short I can get it and still be smooth.