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 full blast.
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.
Cheers John KB6SCO
