[Elecraft] my K2 and its different frequencies.

[Trevor Day]

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 <200508222325.j7MNPfmI035024 at smtp-vbr8.xs4all.nl>, "Carel, 
pc5m" <pc5m at xs4all.nl> writes
>
>
>-----Original Message-----
>From: Carel, pc5m [mailto:pc5m at xs4all.nl]
>Sent: Tuesday, August 23, 2005 1:25 AM
>To: 'Merlarts at aol.com'
>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: elecraft-bounces at mailman.qth.net
>[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Merlarts at aol.com
>Sent: Tuesday, August 23, 2005 12:31 AM
>To: elecraft at 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