[Elecraft] [K3S] intermittent RF path interruption

[Ben Gelb]

Thanks all for the replies.

- I saw the same issue on ANT 1 as ANT 2.
- Haven't dug out a dummy load yet... still TODO.

New clue: Dialing the power down to 8W fixes the RX path (can go back and
forth across this boundary and hear the RX go in and out, coincident w/ a
relay click), but *not* the TX path when in a bad state. So I will still
see 0W out when set to low power. Still have to switch to another band and
transmit to "unstick" the TX path.

So I take this to mean that:
- With high power out, both RX and TX path are impacted by the issue.
- With low power out (<8W, PA clicked out), the problem no longer seems to
be in the RX path (but is still in the TX path).

When I have a bit more time will look at the schematics and see if I can
reason about what might be happening.. feels like this should narrow it
down pretty far. But posting the update in case it spurs any new thoughts.

Ben, N1VF

On Sun, Apr 12, 2020 at 1:03 PM Nr4c <nr4c at widomaker.com> wrote:

> Well first I’d try with a “dummy” load.
>
> The swap antenna to Ant 1.
>
> Sent from my iPhone
> ...nr4c. bill
>
>
> > On Apr 12, 2020, at 3:23 PM, Ben Gelb <ben.gelb at gmail.com> wrote:
> >
> > A bit of a mystery w/ my K3S and I could use help figuring out what the
> > problem might be.
> >
> > Background: I have had the radio parked on 6m for several weeks (HF
> antenna
> > temporarily out of commission) and have left it running (receive) for
> > extended periods.
> >
> > Recently, I have noticed that when I do sit down and try to operate, the
> > radio will get into a mode where during TX the rig will indicate 0W
> forward
> > power during transmit. Following this zero power TX, the RX will also go
> > quiet. Then seems to stay that way for some time (not clear to me what
> > makes it clear up... or if it ever does if left alone).
> >
> > Some experiments I have done to try to figure out what is wrong:
> > - Hitting the tune button also shows 0 power (instead of usual 10-15W)
> when
> > radio gets stuck in this state.
> > - Dialing the power down to where I hear the 100W PA switch out of line
> > (relay click... around 8.0W) seems to immediate restore receive and also
> > causes the rig to make power again on transmit. But when I turn it back
> > past 8.0W, it appears to go back right back into the bad state (so
> suggests
> > whatever the issue is, is in the 100W PA module).
> > - Switching to another band and transmitting momentarily (think I tried
> > 15m) will sometimes knock the radio out of this "bad" mode. But going
> back
> > to 6 meters will eventually cause it to happen again. Usually pretty
> > quickly (several seconds of TX).
> >
> > Some other notes:
> > - Antenna always measures 1.1:1 on the K3S display (when TX working
> > correctly). Also checked w/ RigExpert. I don't think the antenna is the
> > issue.
> > - All my observations have only really been on ANT2 port (nothing
> connected
> > to ANT1 presently).
> > - Haven't really exhaustively tried to test band dependence of the
> behavior
> > because I don't have an antenna on the other bands at the moment and not
> > wild about trying to transmit into a big mismatch. So although it appears
> > 6m related based on my observations, that might not be exactly
> > representative of whats going on.
> >
> > Posting here in case I've given enough clues for someone to suggest what
> > may be wrong or how to narrow down further.
> >
> > Thanks,
> > Ben N1VF
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