[600MRG] NDB Antenna Calculator

[Edward R Cole]

Frank,

OK.  Never in my nearly 60-years in ham radio have I measured Q.  But 
this calculator asks for the Q of the loading coil.  So you are 
saying I have to shell out kilobucks to buy a HP Q-meter.  Sorry, 
that's not going to happen.

I never dipped a choke, either.  I do have my old Heath Tunnel dipper 
but has lain unused for decades - do not even know if it works or if 
all the coils are still there.

I can tell you that my antenna SWR bandwidth is about 5-Hz (F0 2:1 to 
F1 2:1).  That is pretty high Q.  Guess I have to hit the books to 
calculate Q (Z/R right?).  My MFJ is busted so no way to measure Z, either).

73, Ed

At 01:27 PM 9/27/2015, Frank Lotito wrote:
>Ed -I think you may have lost sight of something - A "DC" 
>measurement of coil resistance does not mean anything of consequence 
>w.r.t. to RF losses in an inductor. I assume when you used the term 
>"multimeter" you meant a DC measuring instrument like a VOM, VTVM?
>
>  Besides skin effect losses, there are additional losses that show 
> up at RF.  These additional losses will not show up with a plain DC 
> resistance measurement. For that matter, coil inductance at 1000 Hz 
> (a common measurement frequency for many low-$$ R-L-C instruments) 
> also means little w.r.t. inductance at the operating frequency, and 
> definitely for harmonic frequencies.  For example, I am sure we 
> recall from the old days "dipping out a plate choke" to verify that 
> at the amplifier's operating frequencies the choke does not become 
> series resonant, or take on a capacitive nature at or near the 
> operating frequency.
>
>Have fun, be safe -
>
>73 Frank K3DZ / WH2XHA
>
>________________________________________
>From: 600MRG <600mrg-bounces at w7ekb.com> on behalf of Edward R Cole 
><kl7uw at acsalaska.net>
>Sent: Sunday, September 27, 2015 3:10 PM
>To: sbjohnston at aol.com; 600mrg at w7ekb.com
>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
>
>
>_______________________________________________
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73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
     dubususa at gmail.com