[TenTec] OT: coax versus parallel wire

[Dr. Gerald N. Johnson]

On Wed, 2008-06-11 at 09:29 +0800, Marinus Loewensteijn wrote:
> Jerry & Jim
> 
> Although it is not as loss free as pure open wire I am fond of the 250 Ohm TwinCom. 
> 
> It can be laid like coax and gets little (if any) interference from its surroundings.
> 
> http://www.titanex.de/frames/acc.html

Nice sturdy stuff. Loss should be reasonable up through UHF anyway,
better than coax, though 250 ohms isn't quite a handy value for a simple
coaxial balun to match to a 50 ohm transmitter... but its not cheap.

We used to be able to get a 300 ohm oval shielded twin lead, much
smaller conductors but I found it could handle all the RF voltage I
could generate with a 200 watt final and a big tuner. And it handled all
the short circuit current I could generate with that same tuner series
tuning a chunk of the cable with the opposite end shorted. It was made
by Belden, their number 8290 but is no longer on the market. Its
stranded conductors weren't as big as one strand of the TwinCom cable.
> 
> 73, Marinus, ZL2ML

73,  Jerry, K0CQ