Re: [IRCA] SHORT VERTICALS

[Nick Hall-Patch <nhp@xxxxxxxx>]

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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