Thanks Joe and Chen,
I'm using a series of power and stepped attenuators to couple the K3 to the
SDR-IQ. The input attenuator is underrated a bit so I've been necessarily
limiting transmit time at the higher levels. When time permits, I'll drag in a
directional couple from storage and use it.
Chen does your K3 PA talk back?
Wes
--- On Mon, 7/12/10, Joe Subich, W4TV <li...@subich.com> wrote:
> Can anyone else confirm or deny that their PA talks back to them?
Does not do it here. I've made the same tests
using the SDR-IQ
with the directional coupler from my LP-100 and additional
attenuation for the input to the SDR-IQ. IMD was stable as long
as the power level was stable (Keep ALC at 5 bars and adjust power
with the power control) and not particularly temperature sensitive
although I did not push long key down times.
I also made measurements of transmit image (+/- 30 KHz) using the
FM filter for transmit in SSB and CW (no measurable image within
the range of the SDR-IQ) using the same test set-up.
The only thing I found necessary was to keep the SDR-IQ and K3
separated (could not leave the SDR-IQ set on the top of the K3)
and use good quality cable between the SDR-IQ and directional
coupler to limit any direct pick-up.
73,
... Joe, W4TV
--- On Mon, 7/12/10, Kok Chen <c...@mac.com>
wrote:
For
what its worth, when I ran close-spaced IMD measurements (*very* closed
spaced -- the BPSK31 idle tone :-), I did not notice much drifting in
IMD values once I got the "ALC" meter up to 4 to 5 bars. The transmit
IMD will vary a little (I saw 2 dB) depending on the input drive, even
while maintaining a constant 5 bars on the "ALC" meter. But the
reading was stable as long as I kept the drive stable.
Also, are
you systematically tapping the signal from the dummy load? If you are
just using a short pickup wire on the antenna port of the SQR-IQ, you
could be seeing other artifacts. I had used Elecraft's directional
coupler kit (no one should be without one :-) plus oodles of attenuation
to directly feed the measurement receiver.
73
Chen, W7AY
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