Re: Resources mentioned regarding portable antennas


James Whitehill
 

Bryan,

Thanks for the additional, useful information in this email.  But special thanks for the presentation last night, which excited a lot of interest.  I'm glad you went last, on the principle of saving the best for last!  Your presentation, which you have done before elsewhere, showed polish and efficiency.  Lots of ideas and experiment are embedded in your kit and I think will inspire others, including me, to develop our own kits and antennas.  Well done!

Jim, N0SSM

On Tue, Mar 10, 2020 at 10:46 PM Bryan Nehl <k0emt@...> wrote:
I mentioned a couple of resources at the meeting tonight.

Here are links to them.

“Random Wire Lengths”

https://udel.edu/~mm/ham/randomWire/

http://www.hamuniverse.com/randomwireantennalengths.html

Good lengths in ft: 29  35.5  41  58  71  84  107  119  148  203  347  407  423

Trapped End Fed Half Wave Antennas

http://peanutpower.co.uk/efhw

There are quite a few resources on the internet about trifilar winding a 9:1 transformer.

For the 9:1 and 49:1 transformers you can also wind a primary and secondary on the same core independently.

In the example below L1 (primary) has 3 turns and L2 at 9 turns.  Ratio is 1:3, square that 3 and it is a 9:1 transformer.  Could also easily wind a primary with 2 turns and secondary with 14 turns for EFHW (49:1). 
 
Wired up ~17’ radiator and 6’ counterpoise.  Kx3 had no trouble tuning it anywhere.  Typically I use a 58’ radiator with 9:1 or the trapped EFHW.

The article about portable masts can be found here: http://www.4sqrp.com/4sqrpNewsLetter/201908.pdf

72/73 de Bryan, k0emt


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