[600MRG] Rudy's book...and other info.

Fri Jan 26 15:46:57 EST 2018

As I have previously written, I have a NDB converted to 600m PA.  It 
is made by Southern Avionics and I have the manual for it wherein 
they show a couple antennas.  One is a T with 300-foot top and 
60-foot high.  The output from the matching coil attaches to the 
vertical wire while ground end of the coil is grounded.

Instead of using the internal matching coil I bypassed and ran output 
at 50-ohms via coax to the base of my HB coil placed at the feed of 
the inverted-L.  The NDB has an inductively coupled RF transformer 
with multiple output taps to match a range of load impedances: 5 to 
50 ohm.  In normal beacon use the NDB is located on the ground under 
the vertical wire of the antenna which is connected thru a porcelain 
insulated feedthru lug.  Jumpers enable use of the internal load coil 
which is variable.

But I did not want to locate the beacon outside.

I used EZNEC5 for modeling...mostly to determine radiation resistance 
for making EIRP estimates.  Antenna 3D pattern is much like any 
vertical antenna.  EZNEC did indicate a gain of 1.5  for my 
43x130-foot original antenna; subsequently one tope wire broke so I 
shortened to 122-feet.
http://www.kl7uw.com/630m.htm

73, Ed
XSH ERP calc attached

At 10:18 AM 1/26/2018, J Mcvey wrote:
>About MMana-Gal...
>I tried to model an antique  single wire feed "T" antenna published 
>in a military manual for use with BC654.
>TOTAL FAIL!
>I put the feed point at the bottom of the feed wire and it gave me 
>hundreds of ohms of R and X.
>The radio needs a low impedance capacitive load, so I don't think 
>that's a real result.
>
>I don't think the program does well with antennas that radiate in 
>horizontal and vertical planes?
>
>
>On Friday, January 26, 2018 1:57 PM, Edward R Cole 
><kl7uw at acsalaska.net> wrote:
>
>
>Horizontal wire of inverted-L is a capacity hat as radiation is from
>the vertical wire.
>
>73, Ed
>
>At 08:34 AM 1/26/2018, Kenneth G. Gordon wrote:
> >On 25 Jan 2018 at 23:55, 
> <mailto:lstoskopf at cox.net>lstoskopf at cox.net 
> <mailto:lstoskopf at cox.net>lstoskopf at cox.net wrote:
> >
> > >  I'm going to show ignorance here.
> >
> >Ha ha! Join the club! This is why we have such forums. :-)
> >
> > >  I would think that a capacity hat would be something like a
> > > disc or a Yagi at the top of a vertical pole.
> >
> >Not always. Many here are using "capacity hats" which are simply
> >wires, even one wire in
> >some cases, running horizontally from the top of their verticals.
> >
> >Rudy has an entire chapter which explains the WHY and the HOW of
> >capacity hats and why
> >they are extremely useful at MF.
> >
> > >  A 132 ft sloper would be an antenna with some
> > > impedance at the loaded end resulting from the geometry of the antenna.
> >
> >Well, that is what I thought too, but it doesn't show up that way in
> >the model.
> >
> > >  I would think that
> > > EZNEC should give you some idea of that impedance.  How were the
> > results weird?  Thanks,
> > > N0UU
> >
> >Well, for one thing, I am not using EZNec: I'm using MMANA-GAL, so
> >the results may be
> >different, although up to now, they have been pretty much identical.
> >
> >I suspect that my model is not correct.
> >
> >As I have time, I'll redo it.
> >
> >Ken W7EKB
> >
> >---
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>73, Ed - KL7UW
>   <http://www.kl7uw.com/>http://www.kl7uw.com
>Dubus-NA Business mail:
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>
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73, Ed - KL7UW
   http://www.kl7uw.com
Dubus-NA Business mail:
   dubususa at gmail.com 
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