[Elecraft] [K2] KPA100/KAT100 Control Section Current

[Don Wilhelm]

Brian,

Yes, the KPA100 control circuits must be supplied with current from the 
base K2 so it can switch bands in sync with the K2 - the KPA100 Low Pass 
Filters are in the path from the base K2 to the antenna.  In addition, 
the wattmeter in the KPA100 has to function even though it is not powered.

An additional "wrench in the works" with regard to your plan - the 
KAT100 will not receive power if you unplug the KPA100 power and do not 
separately power the KAT100.  The KAT100 behavior is a little different 
if it is directly attached to the base K2 (the wattmeter in the KAT100 
is used by the base K2)  With the KPA100 in the path, the wattmeter in 
the KPA100 is used to measure the power output level so the K2 can 
adjust the power.

If you leave the SmartCharger in place when you are operating at the 
home station, I would think that will keep your battery topped off with 
no problem - if it does not keep up, just increase the bulk charge rate 
from the SmartCharger, that is only a resistor change.  I assume when 
you operate in the field, the KPA100 and KAT100 are both disconnected 
from the base K2, and battery drain would be as normal for a K2 powered 
by the internal battery.

73,
Don W3FPR

On 9/24/2011 3:49 PM, Brian - N5BCN wrote:
> My current setup is a K2 with a remote KPA100/KAT100 in an EC2 enclosure.
>
> The K2 is powered by a KBT2 that is connected to a smart charger.  The
> KPA100/KAT100 is powered by an external power supply.
>
> I've noticed that the current drain as indicated by the K2's internal meter
> increases 80 mA just by plugging in the KPA100/KAT100 control cable into the
> K2's KIO2.  I see the increase in current regardless if the KPA100/KAT100 is
> off or on (I can also hear a relay latch by plugging in the cable).  I'm
> assuming this extra current is somehow related to the KPA100 and/or KAT100's
> control section?
>
> This has thrown a minor curve ball into my setup.  My goal was to operate
> QRP by simply turning off the external power supply to the KPA100/KAT100,
> but the K2 still provides some 80 mA of current to the external unit even
> when it's off, which I'm sure will have a measurable impact on the battery
> run time.
>
> Any suggestions besides just unplugging the control cable between the K2 and
> KPA100/KAT100 every time I want to go QRP?
>
> 73
>
> Brian N5BCN
>
> -----
> K2 #6800 KPA100/KAT100-2, KSB2, KAT2, KIO2, K160RX, KNB2, KAF2, LP-PAN/K2 w/ Pre-amp, SignaLink USB
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