[amsat-bb] Mirage KP-2 2 meter preamp help

Larry Ryan llryan807 at gmail.com
Tue Feb 16 00:17:11 UTC 2016

I am trying to repair a Mirage KP-2 series mast-mount 2M preamp. It is
quite old. Also, I have the companion bias-tee or Control Box as Mirage
calls it. Also, I have the 70CM Mirage preamp which works really well.

I have contacted MFJ for info and they are very agreeable and they "need to
check one part numbers, etc." but never return a call. When I call them
back, I get the same very polite and agreeable "need to check....".  I have
done this 3 times without getting any info from them.

The problem is not in the Control Box - they both work well with the
working KP-2 70CM preamp.

Have any of you repaired a KP-2 2M preamp?

Do any of you have a schematic diagram of this preamp?

Do any of you know the part number of the gasfet transistor? (I'm thinking
its the problem)

Details:  I have cleaned up and tested the preamp. It seems that the
internal bias-tee relay is working properly and there are voltages on the
transistors that seem to match the working KP-2 70CM preamp. The preamps
were mounted on my M2 circularly polarized arrays at a previous QTH.
Presently, I'm setting up two much smaller antennas and I want to use these
preamps. I'm reasonably sure its the gasfet transistor. I Googled this
topic extensively and I find other hams asking this same question without
an answer in postings from 2001 to 2012. No schematic and no part number
for the gasfet. At $200 each, I want to try to repair it.

Any help would be appreciated.

Thanks & 73, Larry W7DGP

More information about the AMSAT-BB mailing list