[Elecraft] Insensitive Rx and very low Tx output on my K2 Serial No 06574

[Don Wilhelm]

Stan,

As far as I know, a LoP message is only generated when a TUNE is 
attempted and either the KAT2 or the KAT100 is installed.  It indicates 
that not enough power is available for the tuner to do its tune operation.

With only 20 meters as the problem, the source would most likely be in 
the bandpass filter.  Since 30 meters is working, that would point to 
either C21, C23 (the trimmers), C28, C29 or relay K3.
To confirm that the problem is with the bandpass filter, use the RF 
Probe (the parts for an RF Probe were provided with your K2 kit) and 
with the K2 set to 5 watts and connected to a dummy load (if the KAT2 is 
installed, set the ATU menu parameter to CAL P).  Monitor the RF voltage 
at W6 jumper for both 20 meters and for 30 meters (check 40 meters too 
just for a sanity check).  If the RF Voltage on 20 is substantially 
lower at W6, then the bandpass filter is the probable cause.  BUT if the 
RF Voltage at W6 is higher on 20 meters than it is on either 30 or 40 
meters, the problem lies beyond the bandpass filter, and I would suggest 
counting the turns on the 20/30 meter low pass filter toroids L18, L19 
and L20.  Also check the 20/30 meter LPF capacitors C197, C198, C199, 
C200, C2201, C202, and C203 for correct values.

If it is the bandpass filter, check the values of capacitors C19. C20, 
C22, C24, and C16.  Even though these capacitors are also used on 30 
meters, it is possible that the inductors could tune to 30 meters with 
incorrect values, but 20 meters might be a problem.

That is all I can say without further information.

73,
Don W3FPR

sthompson at mypostoffice.co.uk wrote:
> Hi Don
> Your Ref 4A32BAEF.103 at embarqmail.com.
> Many thanks for your speedy response to my earlier query.  I have been
> away for a time and have changed my ISP. The problem is that twenty meters
> does not work, the Rx is insensitive requiring very strong signals for
> them to be heard.  The Tx has a very low output with error message LoP
> being displayed. I would restate that that 30 meters functions normally as
> does 160 meters. The Rant on 20 meters is off and I do not have the KPA
> 100 installed. I have changed antennas without any effect.
> Looking at the circuit diagram it is difficult to see what is only  used
> on twenty meters other than the VCO frequency or possibly some weird
> constructors (me)error. I would welcome any further assistance.
>
> Many thanks
> Stan GI3WTG
>
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