[TenTec] OT 75 Ohm twin feeder

[Dr. Gerald N. Johnson]

On Wed, 2008-06-11 at 07:12 -0500, CSM(r) Gary Huber wrote:
> Try common "lamp cord"... the two conductor parallel kind. depending upon 
> gage of the conductors, you will find them very close to 75 Ohm.
> Obviously not a high power solution.
> 
> 73,
> Gary - AB9M
> www.csm-gh.com
> 
The loss probably depends on the insulation and its color. Probably PVC
insulation will be less loss than rubber, and I'd think white might be
less loss than black (thinking a white oxide as the insulator rather
than carbon black). Published reports in QST of loss of lamp or zip cord
have not been complimentary.

Another RF problem with zip cord comes from lack of control of the
conductor location in the insulation. For 50/60 Hz applications, that's
not critical unless the conductors break through the surface or make
contact or get the insulation so thin between them that it won't stand
250 volts.


Same thing applies to speaker wires, light or heavy duty, and worse many
use a clear insulation that is unlikely to stand up to sunlight.

But while probably not optimum, the losses in these products are not
terribly bad, just not superbly great. Their use is much preferable to
not transmitting at all.

73, Jerry, K0CQ