[TenTec] 75 Ohm twin velocity factor ?

[GARY HUBER]

Common "lamp cord" (parallel conductors), has been used as twin lead and has 
an impedance of "about" 72 Ohms depending on the exact conductor diameter / 
spacing / dielectric rating of the insulation.

Best regards,
Gary - AB9M
CSM(r) G.L.Huber
9679 Heron Bay Road
Bloomington, Illinois 61704
(309)662-0604
www.csm-gh.com
csm-gh at www.csm-gh.com
gary.huber at us.army.mil
ab9m at arrl.net
former National Webmaster for The Society of the Fifth Division
www.societyofthefifthdivision.com
www.csm-gh.com/75thRepoDepo.htm


----- Original Message ----- 
From: "Steve Hunt" <steve at karinya.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Friday, January 26, 2007 3:35 PM
Subject: Re: [TenTec] 75 Ohm twin velocity factor ?


> Folks,
>
> Thanks for all the responses on the Velocity Factor issue.
>
> I would expect 75 Ohm twin to have a lower VF than 300 Ohm or 450 Ohm 
> line. With nothing but air between the conductors the limit on 
> characteristic impedance is 83 Ohms, so to achieve 75 Ohm the line must 
> have a significant amount of dielectric material as a separator; this will 
> tend to lower the VF.
>
> I have an MFJ259B and ZM30 so I could measure it easily enough if I had 
> some. Being a "cheapskate" I didn't want to go buying it before knowing it 
> would do what I want. I guess I'll just have to buy a few metres to test 
> :)
>
> Thanks again.
>
> Steve G3TXQ
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