Was KPA500 RF output wiring: Gary there are several distinctions: First there is a difference between a jumper and a transmission line. For short distances you will have perturbations at the start and finish that will average out because you do not really establish the transmission line effect. Losses are usually insignificant. So to make a twisted pair put two insulated wires in your drill chuck and twist them together. Works great. Things get very different when the distance moves out.
For twisted pair (TP) to be an effective transmission line the twist must be constant. This is called Unified Twist Pair (UTP) Examples of UTP are CAT5 and CAT6 cable. If you twist it yourself the twist will not be constant so you will get dispersion effects and other problems. Dispersion is usually not too big a problem at HF but it does cause phase noise. Rubber (parallel) lamp cord can be used as transmission line and it is cheap. Z0 runs 95 to 120 Ohms depending on insulation thickness. Z0, the surge impedance of coax runs 50 to 91 Ohms. (91 Ohm is pretty hard to work with because the center conductor is so thin.) Z0 runs 95 to 900 Ohms for twin lead but really widens out beyond 300 Ohms (AKA ladder line). The limits for both are determined by physics. You can push them but you can't change them so in short there is no such thing as 50 Ohm twin lead or 300 Ohm coax. Finally if you are making your own TP I suggest you use either Kynar or Teflon insulated wire. Both will be silver plated and have lower losses than copper. 73 Fred, AE6QL -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Gary Hinson Sent: Saturday, September 10, 2011 11:06 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] KPA500 RF output wiring > Sure. Twisted pair is a VERY effective transmission line, and that is > what is needed ... Hey Jim, what kind of twisted pair could I use to feed my [mostly 50 ohm] HF antennas? Coax is expensive in ZL so I'm willing to try alternatives. I'm even thinking of homebrew balanced line with baluns at the bottom (a coax-fed remote antenna switch in my case). 73 Gary ZL2iFB ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
