pc5m, Carel wrote:
I did perform extensive (spectrum) measurements on the TX spectrum at
28MHz...
Example:
TX = 29.0 MHz....
Hi Carel,
Thanks for the data.
While the K2 was never intended to cover the entire 10-meter band (we
spec'ed it in the manual at 28.8), it may be possible to attenuate the
indicated product at 28.51 with a modification to the buffer amp. Or,
it may be that the amp itself is not the cause, but is reflecting a
mismatch back to the TX mixer. A better match may be called for in this
case.
The way to check these possibilities is to temporarily terminate the
mixer and/or the buffer with a 51-ohm resistor, then check the spectrum
again. In either case, a 3 to 5 dB pad at the buffer's input or output
may substantially reduce undesired products. Of course the gain would
have to be made up after the pad (or after the band-pass filter).
Alternatively, you could replace the present buffer with a dual amp
(LT1253, I believe) and configure it for differential output drive
using a broadband transformer.
The K2 has been around for quite awhile, and it's nice to see operators
pushing the envelope with it :) Our policy has always been to keep
track of customer modifications (as well as our own) for possible
future inclusion in the kit. A recent example is the keying
modification, which resulted in the K2 having among the cleanest keying
envelopes of any commercial transceiver.
73,
Wayne
N6KR
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