This is the same problem I had, except I had around a 600Hz shift, and
it took some time to sort out. The eventually problem was indeed the
J310 at Q24. Here is an extract of my exchange with Gary Surrency:
"Right, its now Sunday evening and I've now found the fault. Not having
to
worry about CW filters probably helped to concentrate my mind, and I
reasoned that the problem just had to be associated with the BFO. The
fault eventually turned out to be a defective J310 FET at Q24. It was
allowing a couple of volts to appear at its gate when in Tx mode which
was
sufficient to alter the bias on D37 and shift the BFO when transmitting.
For
reasons I don't understand (as I am not familiar with the way the
firmware
works) this also had an effect upon the audio response when in/out of
CAL
FIL. In any event, not having a J310 to hand I replaced it with a
2N3819
and all my problems disappeared! "
If all else fails, it may be worth looking at this.
gl
Trev G3ZYY
In message <[EMAIL PROTECTED]>, "Carel,
pc5m" <[EMAIL PROTECTED]> writes
-----Original Message-----
From: Carel, pc5m [mailto:[EMAIL PROTECTED]
Sent: Tuesday, August 23, 2005 1:25 AM
To: '[EMAIL PROTECTED]'
Subject: RE: [Elecraft] my K2 and its different frequencies.
Could it be you have an issue with the 8V internal supply ? Maybe on
transmit it is somewhere loaded too much so it will drop and the BFO will
also change slightly ? You could measure at pin 8 of U11.
Also you could verify that the signal called V_BFO is not changed between RX
and TX. It can be measured on pin1 of RP6.
Another possibility could be a faulty Q24 (J310 FET) used for setting the TX
power, normally the impedance on the gate of this FET wouldn't change
substancially if V_ALC is applied, but maybe it is defect ? If you adjust TX
power is the BFO frequency also changing ?
Gl,
Carel, pc5m
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED]
Sent: Tuesday, August 23, 2005 12:31 AM
To: elecraft@mailman.qth.net
Subject: [Elecraft] my K2 and its different frequencies.
Many thanks to all who answered, including those who helpfully suggested
that I might be using RIT or XIT without knowing it.
I just put a frequency counter on the BFO on my K2, and it changes about
70Hz when it goes from receive to transmit. Yeah, I know, there's not
supposed to be any change, but I get a 70Hz CHANGE IN FREQUENCY BETWEEN
RECEIVE AND TRANSMIT.
Freq. counter is loosely coupled to the BFO.
Any ideas?
Merlin, W3ICT
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--
Trevor Day
UKSMG #217
www.uksmg.org
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