[Elecraft] K3 high SWR at end of transmission

[Bob McGraw]

Check the value of PTT RLS.   I use 10 for my K3S.  Also check the value 
of SYNC DT.  Should be FUNCTION.

73

Bob, K4TAX

>
>     1. K3 high SWR at end of transmission (w2yf)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 20 Mar 2026 20:01:44 -0400
> From: w2yf <w2yf.radio at gmail.com>
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] K3 high SWR at end of transmission
> Message-ID:
> 	<CA+_pMJYDgoywTd=-vE=-41EMnkS9QLnCbPHnYGah1ow6tOPzHA at mail.gmail.com>
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>
> I've run into an interesting issue:
>
> I get a high SWR report from the SW; command on a K3 -- only at the end of
> a transmission cycle.
>
> Things I have tested:
>
> - Occurs on ANT1 or ANT2.
> - Occurs when LPA is engaged (5w) or PA is engaged (25w).
> - Always occurs, if transmission is 15 seconds long, or 3 seconds long.
> - Occurs on antenna matched at 1.3:1 and a perfectly matched dummy load.
> - Occurs with ATU engaged and without ATU engaged.
> - Is only at the end of transmission as the transmission envelope is
> falling off
> - I have calibrated the transmitter, identical results as above.
> - All coax has been swapped -- identical results.
> - SWR throughout entire transmission is 1.1:1, but then when PTT closes it
> reports 20.9:1
> - Bar graph on K3 shows no SWR variance at all, from the bar graph
> perspective it is as if nothing is happening with SWR... this only appears
> when polled via the "SW;" command (via Hamlib).
>
> Is this a known bug in the K3 firmware? Is it symbolic of hardware that is
> on the edge of failure?
>
> The fact that it occurs only at the end of transmission and never during
> (regardless of length) is odd.
>
> Tom, W2YF
>
>