[600MRG] NDB Antenna Calculator

[sbjohnston at aol.com]

Some NDB's I've seen had a wire T antenna - equal length horizontal wires from the top of a vertical wire.  One had a three-wire flat-top, with a vertical downlead in the center.  Here's an example 
  
 https://www.flickr.com/photos/32025136@N03/albums/72157632537920879




Steve WD8DAS and WH2XHY

sbjohnston at aol.com
http://www.wd8das.net/
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-----Original Message-----
From: Edward R Cole <kl7uw at acsalaska.net>
To: sbjohnston <sbjohnston at aol.com>; 600mrg <600mrg at w7ekb.com>
Sent: Sun, Sep 27, 2015 2:10 pm
Subject: Re: [600MRG] NDB Antenna Calculator


I played with it and get quite a bit lower radiated power than my 
other
calculations.  I do not know the coil Q so tried some values 
and see R change
accordingly.  So I am guessing if I measure the coil 
resistance with a
multimeter I could find the Q backwards by 
adjusting the value of Q till R
reads what I have measured.

What I am getting is RP =1.97w.  I previously
measured ground 
resistance with my modified MFJ analyzer as 20-ohms.  My
previous 
calculations gave radiation resistance as 0.83.  This calculator

gives is as 0.34 ohms for coil Q=100

I can only guess that the model is a
single wire inverted-L.  My 
antenna has three parallel wires in the vertical
section and two in 
the horizontal top section.  I would guess that would
increase the 
top capacitance and lower the Q of the antenna.  I did my
previous 
modeling with EZ-NEC demo v.5.0.

73, Ed - KL7UW

At 08:34 AM
9/27/2015, sbjohnston at aol.com wrote:

>
>One of the Australian 630 meter
enthusiasts, VK5ABN, has created an 
>online antenna calculator based on
published equations for 
>Non-Directional Beacon antennas.  These are similar
to many of our 
>amateur antenna efforts.  See message copied
below...
>
>Steve WD8DAS and WH2XHY
>
>- - - - - - - - - - - -
-
>
>G'day,
>
>FYI: I've created a web page using equations found in "NDB
Antennas" by
>John R. Pink. to calculate and evaluate antenna parametric. It
can be
>found on
>
>http://ping.net.au/index.php?mode=antcalc
>
>Here you
will also find a link to the original article. This is work in
>progress, so
please let me know if you find any errors or have
>suggestions for
improvements.
>
>I found it very useful in aiding me to improving the
performance of my
>MF antenna.
>
>Enjoy,
>
>73, Berndt
>VK5ABN
>
>
>- -
- - - - - - - - - -
-
>
>
>
>
>
>
>
>_______________________________________________
>600MRG
mailing
list
>600MRG at w7ekb.com
>http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com

73,
Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag
business:
     dubususa at gmail.com