At 09:03 27-12-05, Bill Coleman wrote:
>How much power do you run? If you only run 100 watts, you don't need
>the vacuum-variable caps. Even if you are QRO, you might be able to
>use caps with a reasonable spacing. It all depends on the voltages
>and currents that are present in the matching network.
Right now I'm running 600W, but will hopefully go to a little over a
kW, and I would like to run legal-limit when funds allow.
>A shunt-feed is like a gamma match to the tower. Like a gamma match,
>the difference in diameter between the shunt wire and the tower, as
>well as the length and spacing of the arm determines an impedance
>transformation.
>
>Now, if you could compute all the parameters of your tower and shunt
>arm, you could figure out the exact length, and spacing to make a
>perfect match (or one that you'd only need a little series
>capacitance). Doing so is quite difficult. Figuring this out by trial
>would mean a lot of tower climbs.
Wow...lots of information to digest here in the last couple of days,
and honestly it's a bit much for this relative-newbie to digest
<grin>. I'm wondering if anybody on T-T in the NYC tri-state region
has loaded a tower up and wouldn't object a friendly visit from a
curious newbie? I'd love to actually see this done with the ol'
Mark-1 eyeball to get a real feel of what's involved. Diagrams and
descriptions only go so far. I'm in northern NJ and would be glad to
take a drive to see how this is supposed to look :-). Donuts happily provided!
For that matter, anybody who does this kind of thing professionally,
I'd love to explore that option by e-mail as well since I'm not
really able to climb (no gear or expertise -- at least none yet!).
I'm hoping to get something working before the big 160 contest, but
at this point, I think I may be looking at next season. I'm very keen
on the idea of loading the tower for both 80 and 160, getting a
K9AY-style loop running for receive and maybe a separate 40m vertical
as well. I like the idea of an inverted-L, but the way my property is
configured the only way I could make this work would result in a null
to Europe (horizontal-bit of it running northeast), so that's
probably not the best option.
Again, my profound thanks to one and all who replied to this thread.
Your assistance is tremendously appreciated. Best of 2006 to one and all.
- Peter
W2IRT
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See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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