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Posted: 6/4/2010 11:09:19 AM EDT



http://www.deltaelectronics.com/data/ras10ada.htm

I'm thinking of building one of these. Space requirement is small. They want $445 for the RAS-10A coupler/compensator unit alone.

Anyone know how to calculate the impedance at the center without the coupler/compensator unit? Is the RAS-10A coupler/compensator unit a simple choke balun? 1:1, 4:1, 9:1?

Thanks


Link Posted: 6/4/2010 1:33:25 PM EDT
DO NOT spend that much money on that antenna!!!

For that antenna, a dipole, 1:1 balun, and it is 50 ohms.  And you don't need a balun at all for receive.

All you need is this for the center insulator:

Pick a color, any color...

http://www.universal-radio.com/catalog/antsup/5363.html




and four end insulators:

http://www.universal-radio.com/catalog/antsup/4818.html

or

http://www.universal-radio.com/catalog/antsup/3250.html


Some 14 ga or 12 ga THHN insulated stranded copper wire.

You can get ready made up coax from HamCity.com, or do it yourself.  For receive only, RG-8X is just fine.

Also, if you have a lot of RG-6 (TV coax) you can use that, too.

Prep the connection like this:

http://www.ar15.com/forums/topic.html?b=10&f=22&t=635287

Use 550 parachute cord (aka "paracord") to tie off the ends and support the center insulator.

There, you've made that same antenna for a tiny fraction of the cost.




Link Posted: 6/4/2010 2:38:22 PM EDT
Agree with AFM, that's a crazy amount to spend on a very simple antenna especially for receive.

What do you want to listen to?  It takes complex, large (or else simple and lossy) antennas to cover the entire HF spectrum.  For RX, especially of powerful signals an off frequency antenna would likely be perfectly adequate, but with a little forethought to what you're wanting to receive an antenna can be an excellent performer at several places in the HF bands.
Link Posted: 6/5/2010 2:23:59 PM EDT
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