[Elecraft] Crosspost: K3S FSK shifts RX freq after Xmit

[Chuck Chandler]

Cross-posted to both DXLabs and Elecraft lists, since I am not sure where
the issue lies.

After some experimenting, I find that my K3S will shift the receive
frequency after transmitting in RTTY (FSK D Data mode.)  Finding a busy
band, I can see that if I tune in 5U5R exactly on 14.080.000, then send a
RTTY transmission that after the RTTY transmission ends my rig is now still
showing 14.080.000 on the screen but I am receiving a signal from somewhere
around 14.078.78, near as I can make out from the P3.  There's another data
mode being used down there and the fellow has a nice, strong signal that
comes and goes so I can tell when the signal starts and stops. This happens
when I send from the keyboard as well as from a macro.

I first noticed this in live transmissions but have spent the last half
hour in TX Test mode, and the same thing happens even with no output.

As soon as I tap XFIL the filter setting doesn't change but there the 5U5R
is again.

Alternatively, if I rotate the Shift knob either direction, the 5U5R is
back.  The FC is set to 2.21 kHz.

Alternatively, if I rotate the width control in either direction, it goes
back to receiving the 5U5R.

This only happens when I am using the 400 Hz 8-pole filter or the APF
(which also uses the 400.)  When I use the 2.7 5-pole this doesn't happen.

This feels like something is applying an offset of 1220 Hz while I transmit
and not letting it go.  But I'm at a loss to figure it out.  My digi app is
WinWarbler, and I have AFC unchecked.  It shows a steady freq for xmit and
rcv at 14.080.000 during all this.

1220 is just about half of 2210, so there's that.  Also, the K3S TX Test
mode doesn't key the finals, so there's no RF getting into it.

This feels like something is set wrong, but blimey if I can figure it out.

73 de Chuck, WS1L
-- 


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Chuck Chandler
chandlerusm at gmail.com
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