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

[sthompson]

Hi Don
Your Ref [hidden email].
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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[Don Wilhelm-4]

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

[hidden email] wrote:

> Hi Don
> Your Ref [hidden email].
> 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
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
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> Please help support this email list: http://www.qsl.net/donate.html
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