Bingo... Guy put one over the fence and outta the park with that one...
Hi, Jim
Well, an inductor and a choke are TWO devices instead of one.
We've all heard of KISS.
As it stands now with what we recommend, the fellow has an antenna
wire up in the trees connected to the transformer, an FCP wire
connected to the transformer, a toroid winding in the box, and a coax
jack back to the shack. Simple. Excellent common mode block INCLUDED,
no extra cost, in the bargain. Looks like a balun on the dipole. And
the 50 ohm coax to the shack is decently matched. Might have all been
done on purpose.
Resonance is overrated. It it not necessary for radiation. 5/8 wave
vertical is not resonant. Double extended zepp is not resonant. Lots
of antennas not resonant. Resonant counterpoises are a design choice
with something in mind. They are not required.
Monkeying with the FCP size and spacing cannot be done properly unless
one is doing near field horizontal N x N horizontal sample points
below ground with a model that does NOT include the vertical radiator
(yes, there is a way to do that). The field values are squared and
summed. This bypasses ground approximation issues in the modeling
program. The main point of the FCP is to minimize radiation, and
minimize induced currents in the ground.
As I recall, maybe a thousand models ago, running the ground field
squared integration, 4 inches was at the point loss fields (from the
FCP only) started increasing with larger spacings.
All my early attempts at this were with resonant folds. I had been
trained that resonance was one of the ten commandments. Been there,
done that. But never let it be said I denied a man his own discovery
process. Have at it.
Don't get me wrong, there are specific advantages to resonant 1/4 wave
radials. But the single wire 5/16 wave folded counterpoise is not a
radial, and is specifically non-resonant, on purpose.
We're not trying to attack the various schemes of modern science, just
get small lot guys on 160 and keep the KISS.
73, Guy.
On Tue, Jul 31, 2012 at 12:59 PM, Jim Brown <jim@audiosystemsgroup.com>
wrote:
> On 7/31/2012 7:19 AM, Tom W8JI wrote:
>> The capacitive reactance FCP and inductive reactance matching transformer
>> form a tuned system. The combination acts like a single short-length
folded
>> inductor-loaded "radial". This is why voltages are so high, and why only
one
>> particular coupling system works.
>
> Elegant analysis, Tom. Thanks. I looked at Guy's very well done piece
> in the National Contest Journal (the one timed for reading on the
> airplane going to Dayton) and wondered why a serious common mode choke
> would not work.
>
> Guy's dimensions are quite specifically tailored to fitting in a small
> space, so it would be nice to keep it there. So The obvious next
> question is, is there any reason why Guy's 66 ft FCP could not tbe made
> to work by adding that inductor and a suitable choke? Or perhaps
> another fold?
>
> 73, Jim K9YC
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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