If you have a high impedance scope probe around the shop Mark, then
hook it up to your "spectrum analyzer" the Perseus. See what the
response looks like with scope probe at the transformer output, and
its BNC feeding the Perseus. Then try one of the other
transformers. I'd be curious to see if there was a peak in the
response without anything loading down the vertical/matching
transformer combination.
best wishes,
Nick
At 21:19 01-03-14, you wrote:
That was my guess as well, Nick...altho the array doesn't seem to be
freq-sensitive (i.e. a 4:1 and a 16:1 deliver the same relative
signals at both ends of the band).
Otherwise...I like your 'antenna-tuner' idea :-))
Regards,
Mark Durenberger
-----Original Message----- From: Nick Hall-Patch
Sent: Saturday, March 01, 2014 2:07 PM
To: Mailing list for the International Radio Club of America
Subject: Re: [IRCA] SHORT VERTICALS
What is the inductance of the 200 ohm winding Mark?
My guess is that there's nothing a short vertical (which has a
capacitive impedance) likes better than a little matching inductance;
it's like a loading coil. You might find that your improved
sensitivity actually has a bit of a peak at a certain range of
frequencies, perhaps damped by your receiver's 50 ohm
impedance. Maybe see how well some of the higher ratio matching
transformers do at LW beacon frequencies in comparison?
Next step, built a tapped matching transformer, and use your
transformer as an antenna tuner perhaps?
best wishes,
Nick
At 14:27 01-03-14, you wrote:
I'm wrapping a 2,000-mile road trip and have occasionally stopped,
to stick up my 30-foot modified Dallas Lankford vertical. And
something's been bothering me.
Lankford's heritage 'short vertical' proposes a 4:1 base
match. I've played with this ratio, from 2- to 16- : 1 and,
indeed, 4:1 seems best. That would suggest about a 200-ohm antenna.
But why? 30 feet at MW = about 200 ohms? Doesn't seem right...
Scratchin' my pate and anticipating wisdom from the list...
Mark Durenberger
On the Road
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