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Homebrew Balun Wire

Feb 14th 2018, 09:05

W9KJO

Joined: Nov 17th 2015, 10:54
Total Topics: 0
Total Posts: 0
A few months ago there was an article about building baluns for antennas in QST. I have been doing some research and wish to build a few baluns. However, what type and size of wire is still not clear to me.

I have been told to use Teflon Coated wire, Is this a good example of teflon coated wire? https://powerwerx.com/ptfe-high-temperature-stranded-wire?gclid=EAIaIQobChMI19fAyNSl2QIVVzVpCh1HJwlVEAQYAyABEgJvyvD_BwE

Also, what Gauge wire would be needed for,

1. 300 watt application
2. 1.5kw application

Thanks for any clear answers that might be offered.

73, W9KJO
Feb 14th 2018, 09:21

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Yes, that is Teflon coated wire. Sometimes you can find good deals from surplus sources, though not like you could 20 years ago. Ebay has pretty much established a market price for this commodity.

The ideal gauge is the one that results in the lowest balun losses. This can be determined via measurements and trial and error. As far as I know there is no "formula." Unlike direct current losses, RF losses include something known as the "proximity effect" in which conductors in close proximity will have additional loss. Thus, the thickest wire that will fit is usually not the optimum size.

I typically make two baluns and connect them back to back, to allow insertion loss measurements with a low power transmitter and a precision wattmeter. Though in retrospect "low" power was all I had at my disposal. High power testing may make it easier to use an IR camera for design evaluation, if you have one available.

Zak Lau W1VT
ARRL Senior Lab Engineer
Feb 14th 2018, 13:20

W9KJO

Joined: Nov 17th 2015, 10:54
Total Topics: 0
Total Posts: 0
Thanks for the response. However I need more information on wire size as this wire is very costly and experimentation would be cost prohibitive.

What size wire do you use for,

1. 300 watt balun
2. 1500 watt balun

HF Bands. 80M, 40M, 20M, and 160M

73, W9KJO
Feb 15th 2018, 10:28

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
In that case you are best off copying someone else's design as accurately as you can.

While I investigated transformer design years ago, I never looked at anything for those power levels, as I didn't have anything that put out that much power.

The lab no longer does such projects, as the focus of the ARRL Lab has changed to membership contact via email and phone, leaving no time for costly R&D.

Jim Brown K9YC has published balun designs on the Internet--I believe Google.com has cached "virus free" copies for download.

S E Hunt G3TXQ has an excellent collection of coax wound choke or 1:1 baluns at http://www.karinya.net/g3txq/chokes/
Instead of RG-58 you could wind the chokes with Teflon RG-400.

The dielectric losses of PVC wire should be negligible at HF. You may be able to get a very good idea of the losses and low frequency response by measuring baluns constructed out of PVC insulated wire. The higher dielectric constant of PVC wire may be expected to result in a quicker higher frequency rolloff compared to Teflon covered wire, but actual results may vary due to differences in insulation thickness and construction technique.

The lack of clear information may be due to the difficulty of designing baluns that will survive in the real world. Just like it has been historically difficult to be a Cleveland Browns quarterback--two dozen talented young men have tried and failed.

Zak Lau W1VT
ARRL Senior Lab Engineer

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