K2/KPA/KAT operation WITHOUT high-current power

[Chris Kimball]

My rig is a K2 with a KPA/KAT in a separate enclosure.  The rig will operate at 10W or less with the power turned down, but I'm taking additional current drain from the presence of the KPA/KAT.  

I'd like to simply disconnect the high-current supply from the KPA/KAT to operate a low power and lower current drain without completely disconnecting the KPA/KAT.  (The K2 has the low power antenna tuner.)

This  seems reasonable from the KPA manual and the KAT should become a straight through connection.  However, the KPA schematic says that the passive low pass filter will remain in place. No problem with that in principle, however, will the correct band settings occur without the high-current supply in place?  There's no straight through connection around the filters that I can see.

Chris
NQ8Z

[Don Wilhelm-4]

Chris,

The answer is YES (almost, see comments on the KAT100 below) - just turn
off the power to the KPA100/KAT100 to operate QRP.
The voltage to power the KPA100 microprocessor and relays is provided by
the 12CTRL line from the base K2 for exactly that reason.  The KPA100
LPF is still in place.

The only potential problem is presented by the KAT100.  Without power,
it will not pull in any relays to provide tuning for your antennas and
the antenna will be forced to the ANT1 jack - that will work just fine
if all your antennas are resonant.
With that condition present, the KAT2 will be feeding the input of the
KPA100 LPF which means the KAT2 will have to be in bypass.
You can avoid that problem in one of 2 ways.  1) disconnect the internal
power cable between the KPA100 and the KAT100 and power the KAT100 from
the same power source that is used for the base K2 - the KAT100 will
continue to work even if the KPA100 power is off - no change in
configuration when switching to QRP operation, just turn the KPA100
power off.
2) Disconnect the control cable to the KPA100/KAT100 and connect your
antenna(s) directly to the KAT2 and operated the base K2 and its KAT2 as
a separate QRP rig.

73,
Don W3FPR

On 4/12/2013 9:31 AM, Chris Kimball wrote:

> My rig is a K2 with a KPA/KAT in a separate enclosure.  The rig will operate
> at 10W or less with the power turned down, but I'm taking additional current
> drain from the presence of the KPA/KAT.
>
> I'd like to simply disconnect the high-current supply from the KPA/KAT to
> operate a low power and lower current drain without completely disconnecting
> the KPA/KAT.  (The K2 has the low power antenna tuner.)
>
> This  seems reasonable from the KPA manual and the KAT should become a
> straight through connection.  However, the KPA schematic says that the
> passive low pass filter will remain in place. No problem with that in
> principle, however, will the correct band settings occur without the
> high-current supply in place?  There's no straight through connection around
> the filters that I can see.
>
> Chris
> NQ8Z
>
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/K2-KPA-KAT-operation-WITHOUT-high-current-power-tp7572518.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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