Ed,
A couple of other thoughts on this, assuming that no relays are
switching as you vary power from 80-120 W (see previous e-mail).
We need to get an o'scope on your TX output at the time the SWR goes up
to see if the PA is unstable. If it isn't, then perhaps the SWR bridge
transformers are getting saturated, or there's RF getting into the SWR
bridge op-amp.
If it's the PA going unstable, the next step is to have you put in the
KANT3 module rather than the KAT3.
Wayne
On Sep 17, 2007, at 9:26 AM, Ed Muns wrote:
On your 100W+ SWR problem (going wild after having been
1.0:1): once this has occurred, doing a TUNE (not an ATU
TUNE), does reducing the power back below some threshold
restore the SWR, or does it remain high?
The higher SWR is only at 115 and 120 watts. No problem reducing
power and
having the SWR return to 1.0:1, so I'm assuming there is something
still
going on in the KPA3. All measurements are done by using TUNE to read
the
actual power and SWR. (I did a TUNE at 5 and 50 watts on all bands
before
redoing the measurements.) Attached are updated tables of data for:
1. 50 ohm load, KAT3 bypassed.
2. Antennas, KAT3 bypassed.
3. Antennas, KAT3 tuned.
It was at a power request of 120 watts and inflated SWR on 20 meters
that
K6XX heard the problem with my signal. At 100 watts, the problem went
away
(as does the inflated SWR). For FCS, maybe the firmware should limit
power
to 100 watts, at least until the KPA3 can be fixed at the higher power
levels?
Ed
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