[Elecraft] K2 - REMOTE KPA100/KAT100

[Jim Wiley]

Chris -


I built up the KPA-100 / KAT-100 combo earlier this year.  I second 
Don's comments, and have a few more: 


Build and test the KAT-100 first.  Get the KAT-100-2 version which has 
the larger enclosure.   


If you are installing the KAT-100 and the KPA-100 in a separate 
enclosure, and will always have them assembled this way, then there are 
a few things that can be omitted when building the KPA-100.  
Specifically, the internal RF cable that goes from the KPA-100 board to 
the K2 main board.  This function will be provided by the BNC-BNC cable 
mentioned below. 


The multi-colored control cable will reach between the proper connectors 
in the amp and tuner without modification.  Same for all other 
interconnects.


I also skipped the steps involving mounting of the speaker on the 
KPA-100.  Since I was going to leave the K2 pretty much "stock", I chose 
to leave the K2 speaker in place.   As in the RF cable (above), this 
means that the cables and connectors intended to bring speaker audio to 
the KPA-100 mounted speaker are unnecessary, and may be omitted.   You  
end up with a "spare" speaker this way, which may be useful for some 
other project.   Same for installing the magnetic shield on the speaker. 


I covered the hole (in the KPA-100 heatsink) that would have existed 
because of the not-used speaker with some scrap plastic, painted flat 
black.  Glued it in place with  RTV cement (bathroom sealer).


Do take Don's advice and get the KIO2 module. 


Remember that the antenna switch and power level indicators on the 
KAT-100 will not operate properly unless the high-power 12-volt source 
for the KPA-100 / KAT-100-2 is on before the K2 is powered up.  I think 
you can do them simultaneously, but have not tried this. 

 
I decided, after reading about the use of transistor thermal pads and 
the need for re-tightening the mounting screws periodically, that I 
would try the use of semiconductor thermal grease instead.  This is a 
white compound commonly sold as "heat sink compound", and is available 
from Mouser electronics, among other vendors.  I think it is a mix of 
silicon grease and zinc-oxide.  It might even be available from Radio 
Shack.  Hopefully, this  compound, while somewhat messy to apply, will 
make re-tightening the screws unnecessary.  If you decide to use it, 
remember a little goes a long way, and be sure the counting surface of 
the transistor is evenly and completely covered with a _thin_ layer.  
Any excess will squeeze out of the way when the mounting screws are 
properly torqued.  I have used this stuff for years and years, and never 
had a failure attributable to lack of thermal contact between the active 
device and whatever heat-sink was being used. 


Good luck with your upgrade!


- Jim, KL7CC



Don Wilhelm wrote:
> Chris,
> Installing the KPA100 and KAT100 together in an EC2 enclosure is 
> really easy.  Order the KAT100-2 and you will have all the components 
> needed to connect the KPA100 into the KAT100 board.  You will need a 
> cable to connect from the KIO2 to the KPA100 (or the KAT100) DE9 AUX 
> I/O connections - the materials needed are provided with the KAT100 
> kit.  In addition, you will need a short piece of coax with BNCs to 
> connect from the K2 antenna output to the KAT100 AUX RF input.  
> Another short piece of coax with PL259s is needed to connect from the 
> KPA100 RF output to the KAT100 ANT IN.  If you already have the KAT2 
> installed in your K2, it can stay - when the K2 determines the KPA100 
> is connected it bypasses the KAT2 and provides RF on the KAT2 ANT1 
> connector.
>