It is working well, and possibly because it is buried except a short
distance at both ends. I was avoiding burying a non shielded, twisted pair
with possible varying losses due to
changing ground conditions.
73
Bruce-K1FZ
On 8/12/2013 1:42 PM, Bruce wrote:
I am using a twisted pair, with shield, that is near 55 ohm
impedance for
my receiving delta loop. The cable is designed for audio,
Depending on the nature of that cable, you're probably better off
without the shield if both ends are transformer-isolated as I described.
There are two potential problems. First, the shield provides a lovely
path for common mode current, which can couple noise via Pin One
Problems to a rig. Second, if the cable shield is foil plus drain wire
("rack wire" like Belden 8451), shield current will be STRONGLY coupled
to the twisted pair by a mechanism that Neil Muncy named
"shield-current-induced noise" (SCIN). The mechanism is that the drain
wire has the same lay as the signal pair, and is manufactured so that it
is much closer to one conductor the pair than the other. This results in
more inductive coupling to the closer conductor, converting the common
mode current to a differential voltage.
73, Jim K9YC
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