Open wire (or 'parallel conductor') feed lines connected to a reasonably balanced load do NOT radiate (or receive noise, etc.)
The currents, hence the electric fields, around each wire are opposite and equal at all points, even though the line may have a high SWR. Those equal and opposite fields cancel, meaning no radiation from the line nor can an external RF field induce a current in the line. Note that a "perfect" open wire line has two attributes. Both conductors are in the same physical space - a physical impossibility - and the load is perfectly balanced - physically more possible but not common. However, spacing the wires a small distance apart (in terms of wavelength) and a reasonable amount of balance in the load still results in a transmission line that is as free from radiation or unwanted pickup as many coaxial lines. Note that coaxial line itself suffers from the fact that the outside of the shield is a conductor at RF completely separate from the inside surface of the shield, since RF travels only on the surface of a conductor, not "through" it. So, if you have 50 feet of coaxial line running from your antenna to the rig, you also have a separate 50 foot random wire antenna leading into the shack. That's why special care must be taken to control or suppress currents on the outside of the shield to avoid "RF in the Shack" issues with coax. Ron AC7AC -----Original Message----- Those of you using open wire feed lines. How do you keep RF out of the shack? 73 George/W2BPI K2/100 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
