So, I got my KXPA100 kit and have assembled it. But I'm having trouble
keying it with my transceiver (HPSDR Hermes with alterations to support
driving the KXPA100). My circuit didn't have any trouble keying my
previous amp (a HFPacker V4). If I manually short the KXPA100 key input
things appear to work in the limited testing I've done, so I don't think
there is anything wrong with the KXPA100.
I've measured 5V as expected at the key input, and I've measured the
current while connecting the KXPA100 key input to my transceiver. I'm
measuring 0.58 mA when the transceiver attempts to key the amp. The
KXPA100 manual says that the key current will be 1 mA max (if I am
reading that correctly) so this seems to be about right. Is there a
minimum current requirement? There is a 560 ohm resistor in series
internally, along with diodes (one in line with the key output to the
KXPA 100 and one inline with the key output to the internal tx preamp)
to prevent interaction between the two.
Any ideas? My next experiment will probably involve changing or
bypassing the 560 ohm resistor, but I have doubts that will fix the problem.
John
AC0ZG
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
