I've just noticed something interesting about my Ten Tec 229B tuner. It
happens on 80m-30m, where the center switch is in positions Lo2 - Lo5
and various fixed capacitors are switched into the circuit.
I use non-resonant antennas fed with ladder line. I normally tune the
tuner with a noise bridge or at 10 watts. Then, when I operate at 100
watts, I notice a slight upward creep of SWR over a few seconds after
key-down. Then the SWR backs down a little and remains stable while I'm
transmitting. The creep is very slight, from 1:1 up to maybe 1.2 or
1.3:1 on my IC-7300's SWR meter. My guess is that this is the same
issue some people report with the Ten Tec tuners on 160m. On low
impedance loads that require the extra fixed capacitors to switch in,
those capacitors warm up slightly and change value as we transmit.
I never noticed this before. But I just picked up a used Daiwa CN-101L
cross-needle SWR meter, because the tuner's switched meter and the
IC-7300's multiple displays make monitoring SWR inconvenient. The
Daiwa's "reflected" readings are a bit overly sensitive. On that meter,
I could clearly see the creep happening. Sure enough, when I looked on
my IC-7300's SWR meter, it was happening there, too. The Ten Tec tuner's
meter barely shows it, if at all.
My guess is that everything is fine. The SWR creep is too small to
endanger my finals, and I can always touch up the tuning. I just want
to be sure that the SWR creep doesn't indicate that the fixed capacitors
in the tuner are failing. Can someone give me a reality check?
Thanks and 73,
--Peter, KD7MW
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