Coax for a balun

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Glenn
Posts: 8
Joined: 12 Feb 2016 15:39

Coax for a balun

Post by Glenn » 22 Mar 2016 18:50

Hello Everyone,
Does anybody know of a source for small quantities of RG-6 which has a STATED, reliable, velocity factor?
I'm building a matching balun for my Korner 9.2 and I'd really like to find some stuff with a good single layer of copper shield which can be soldered easily. Most of all it needs to list it's velocity factor so I've got something to go by when factoring the length of the balun.
So far I'm just seeing "quad shield" stuff at .90 VF and I'm thinking that 2 layers of aluminum shield and a couple of layer of foil might screw up the formula. Plus, aluminum doesn't solder so well.
It's out there, I just don't want to buy a 500' roll. More like 25' or less.

Kind Regards,
Glenn

k6sti
Posts: 63
Joined: 20 Oct 2014 17:27

Re: Coax for a balun

Post by k6sti » 22 Mar 2016 19:58

Glenn, I don't know where you can get a short length of RG-6 with complete specs, especially with a copper shield. I'm not sure RG-6 is made except with an aluminum shield. But note that you don't need to restrict your search to 75-ohm cable. The optimum impedance for a halfwave coaxial balun is 150 ohms. 93-ohm RG-62 will work fine and it has a copper shield. Here's one place that sells it by the foot and specifies the velocity factor. I don't know if they have a minimum order amount.

http://www.pasternack.com/flexible-0.24 ... a-u-p.aspx

You can also look for Belden 8254. It is 93 ohms with a copper shield and a velocity factor of 84%. Other possibilities are Times Microwave LMR-200-75, LMR-240-75, and LMR-300-75. These are 75-ohm cables with a tinned copper shield.

Brian

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Glenn
Posts: 8
Joined: 12 Feb 2016 15:39

Re: Coax for a balun

Post by Glenn » 28 Mar 2016 15:33

Thanks Brian,

I don't know how their website got by me. Lot's of good stuff!

Glenn

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