|[AMRadio] I'm not an antenna expert|
jpl15 at panix.com
Wed Jan 11 13:05:59 EST 2006
On Wed, 11 Jan 2006, W5OMR/Geoff wrote:
> There's no law that says you have to run full power output, to tune SWR on an
> impedance matching device...
Ooops - I should have clarified that - I do not run full power to play
with the tuning - actually I run the minimum I can get the Valiant to put
out, by decreasing the coupling to as little as possible, and tuning the
transmitter up at that output - usually 20-30 watts. THEN I load 'er up to
> I'd just as soon use a solid state rig, that has SWR protection in it...
> slowly adjust the impedance matching device, until you get full output of the
> ricebox, and minimum standing wave ratio. Then, DON'T TOUCH IT! Just switch
> rigs, and tune the transmitter to that setting. it's resonant.
Except that I don't seem to be able to achieve much in the way of
'resonance' on the affected bands - the tuner settings get very
'squirrely' and of course the transmitter tuning goes wildly off as those
adjustments are made - as opposed to the bands where the antenna/feedline
is "happy" - then it's stable, and an easy matter to arrive at a logical
setting for the system.
One of the drawbacks to the pseudo-NVIS arrangment is that it is like a
'searchlight' directed straight up to a cloud-deck in the sky - the light
is diffused back down, as opposed to a more directional distribution of
radiated flux - so I really need to have an electrically efficient antenna
system as I can, give my particular constraints.
But the question I still have is - what do you think of modifying the
Loop into a dipole - I'm going to try it anyway, just for the halibut -
but I have also thought of replacing the ladder-line with coax and a balun
at the feed point - dunno yet.
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