[Elecraft] KPXA-100 & K2 Integration?

[Dave Van Wallaghen]

Hi Ken,

I service all of Elecraft's Classic Line of Products through my company 
W8FGU Services, LLC and I am a part time employee of Elecraft doing the 
same thing for them. I can assure you that discontinuing the KPA100 was 
no arbitrary decision. As with most 20 year and older designs, part 
availability becomes more and more of an issue with every passing year. 
When we were not able to procure the finals anymore, I believe this was 
one of the final straws. They stopped producing the finals a couple of 
years ago as far as we can tell. There are some counterfeit versions on 
the market and auction sites, but the are not up to spec. This combined 
with other unavailable parts led to the demise of the KPA100. I worked 
pretty hard with Wayne, Eric and our parts folks to come up with a 
solution, but in the end, it was decided to discontinue it.

I am actively working on a project to create cables that will interface 
the K2 with each of our amplifier products including the KXPA100. With 
the addition of a keying line from the K2, you can form a basic 
integration to most any amplifier. The basic 10 watt version does not 
have an external keying line and would need a keying circuit added to 
the K2 bring it out. There are a number of circuits documented out there 
for this purpose. I also sell a kit for doing this on my website: 
https://www.w8fgu.com/k2_trdriver.html. This circuit and kit was based 
on one produced years ago by Tom Hammond, N0SS (SK). If you have the 
K60XV module installed, then you can bring out the K60XV J2 pin 2 for 
this purpose. I am doing exactly that on my K2. I mounted an RCA jack on 
the rear panel and tied it to that pin.

The above will allow the K2 to drive an amp, but will not get you much 
"integration". With our amplifier line, band switching can be automated 
with a dit of RF from the K2. But other than that, tight integration 
like with our newer transceivers is not there. The cables I am trying to 
develop will attach to the K2's KIO2 AUX I/O port and provide keying. I 
have prototyped one to work with the KXPA100 and it keys properly and 
allows RS-232 commands to pass through the KXPA100 from the PC for 
control of the K2 by software programs. The main issue with integrating 
the K2 with our amps is that there is virtually no codes space left in 
the K2 firmware for having it communicate and integrate with the other 
amps like it did with the KPA100. So, things like amp power output and 
SWR will not be reflected on the K2 like it does with the KX2 & 3 when 
used with the KXPA100.

For use with the KPA500 and KAT500 Power Combo and the KPA1500, I am 
going to prototype similar style cables for those amps as well. The good 
thing we've found with the Power Combo is that you can set it up to poll 
for frequency info from the K2 so that you have automatic band switching 
and proper loading of ATU memories while tuning around with the K2 VFO. 
The KPA1500 has the same capability but will require some modification 
of the cable as it is not implemented the same way as the KPA500. At 
this point the KXPA100 does not poll at all unless it recognizes the 
XCVR as a KX2 or 3.

So, "full integration" may not be totally possible because of the lack 
of code space in the K2. But I believe I can get some "nice to have" 
integration like automatic band switching and ATU memory loading with 
our amplifier line. I am working closely with my tech counter parts at 
Elecraft to bring these cables to fruition soon we hope. Stay tuned...

73,
Dave, W8FGU


On 1/29/2022 1:01:33 PM, "KJ" <kjpj27 at gmail.com> wrote:

>Hello again all,
>Can the KPXA-100 be fully integrated with the K2? Full QSK and so on? Appears to be mostly for the KX3 and KX2.
>My 2003 K2 has all the options.
>
>I can't believe Elecraft discontinued the 100w amp for the K2. What do have then?
>A full featured, basically, QRP radio! These little 5 watt jobs are 1/8th the size but maybe w/o all the bands and there all over the place for sale.
>
>Should have bought the KPA-100 back then but the $$ weren't there!!
>Anybody has one up for sale....let me know....
>
>Thanks!! Ken
>W2GIW, QRZ address is good.
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