Bruce and Jim: I will have 9:1 transformers at both ends of the antenna (going to make it "switchable" for east and west directivity) as well as a 2:1 transformer just prior to the input to the shack. Won't bury the cable - run it "above the rocks" at 2 to 3 feet above the lousy ground we have around here in s/w Utah. Appreciate the insight !!! 72, Jim Rodenkirch K9JWV
> From: [email protected] > To: [email protected] > Date: Mon, 12 Aug 2013 15:00:32 -0700 > Subject: Topband: CAT5 twisted pair > > 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 > > _________________ > > Topband Reflector > > > > _________________ > Topband Reflector _________________ Topband Reflector
