[TowerTalk] ? Yagi Interaction on 15m: KT34XA and XM240

[Pete Smith]

At 11:07 AM 10/26/00 -0500, Todd Dravland wrote:
>I have noticed on my TS940s wattmeter/ vswr that when running 5 watts
>the vswr is typically lower than with 100 watts.. what I am getting at
>is that I don't believe my feedlines are ideally decoupled from the
>antenna, due to either not good enough balun isolation or perhaps the 50
>ft. horizontal run of feedline to the shack.  In any case, have seen
>VSWR change with increasing power.

The various SWR indicators we use are all subject to error, IMO.  I can
take my pick between my TS-930's SWR meter (probably similar to your
TS-940) and the VFD that is on the far side of my amp.  Not surprisingly,
considering what's inside the amp, even on bypass, the two SWR readings are
somewhat different, but what's maybe more interesting is that the SWR seems
to increase on the VFD by about 5 percent when I go from 100 to 1000 watts
power.  I suspect this is traceable to calibration, and is probably not to
be fussed about.

In the case where all the measurements are being made with a Drake W-4, I'd
suspect calibration has a lot to do with the difference between 100 watt
and 1000 watt SWRs.  It would be interesting to know what happens to the
SWR reading when feeding a known flat dummy load with 100 vs 1000 watts on
various frequencies... 


73, Pete Smith N4ZR

Contesting is ... Extreme Radio

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