Tuesday, May 10, 2016

Twisted dummy

Improving the ugly dummy load

A few months back I built an ugly dummy load using the simplest method I could...

I soldered 20 2watt 1k ohm resistors across two pieces of romex wire and soldered it to a UHF connector.  Voila, had a 50ohm dummy load effective for extended QRP use and brief bursts of QRO power.  But as I analyzed the balun and noted in the previous post, some capacitance due to the simplistic design made it less than perfect at higher frequencies.

I got to thinking that the capacitance might be lessened by making those two antenna looking pieces of wire used in the balun into a different shape.

Croissant Balun

Twist and shout

So I twisted the parallel wires of the balun into a concentric loop  like a croissant and the result was promising.  Reactance is a bit less from 20m through 15m resulting in the SWR remaining as flat as my MFJ commercial balun.

Think like a Thermian - Never Give up, Never Surrender
Yes, I have an odd choice in favorite movies

So when you have a project that doesn't work quite as expected keep the little grey cells churning.  You'll likely come up with some alternatives. If someone who understands RF can explain to me why this helped I'd like to know. 

This ugly balun is going fellow Ham who is getting back into the hobby following a hiatus and is in need of a balun.  This balun is still not ideal but it's become more useable and the parts cost less than $10.

That's all for now

So lower your power and raise your expectations

Richard, AA4OO

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