[TowerTalk] Short-Snort

[Dick Green]

I must have zipped by and deleted the original post on this topic. Could
someone forward me a copy? Thanks in advance.

BTW, the Kenwood TS950SDX lets you adjust the rise time of the CW waveform
from 2ms to 8ms. Wouldn't lengthening the rise time allow time for the ALC
to ramp up? I think I'm seeing the effects of transients when driving my
Alpha 87A amp from the '950, especially when sending fast CW from the
computer (CT, for example) in full break-in mode. When the rise time is set
at 2ms I see random spikes to infinity on the '950's LED SWR meter. As I
increase the rise, the frequency of the spikes gradually diminishes and they
disappear at 8ms. Anybody else ever see this?

I've never been able to figure out why the spikes show up as an increase in
SWR. I've used a dual trace scope to check the timing on the T/R pulse from
the '950 to the Alpha (I use a homebrew bipolar transistor interface)
against the CW waveform, and it clearly shows the T/R signal rising well
before the CW waveform begins (as I recall, it looked like the timing
diagrams in the service manual.) So, I don't think the Alpha isn't switching
in time (unless those PIN diodes are really slow.) Anyway, if that was
happening I think it would generate a TR sequencing fault in the Alpha. If
there really is a transient, it must be happening so fast that the Alpha
doesn't get an "overdrive" fault. Anybody have any ideas what's happening
here?

I realize that this sounds OT, but I have a related problem that always
happens under the same conditions -- fast CW from CT -- that generates a
fault in the Alpha listed as "severe mistuning or possible RF arc". Happens
most frequently on 10M and 15M. I suspect that there's some sort of arcing
going on in the TH7 traps when this happens (there's the on-topic part of
this post!) I *think* it happens more often in the rain, but since it
invariably happens on the first dit of a transmission, I've suspected that a
transient from the '950 is causing a very short but very high power spike
from the Alpha, which in turn is causing an arc in the traps. Anybody think
that idea has merit? (BTW, I've been advised by more than one person that
TH7's do have arcing problems on 10M and 15M at 1500W, especially in wet
weather.)

73, Dick, WC1M





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