On 13/11/17 23:10, Don Wilhelm wrote: > The proper place to cure "RF in the shack" problems is in your antenna > system. A good common mode choke (many call it a balun) in the antenna > feedline and running the feedline at right angles to the radiator > (assuming a dipole) to keep the feedline from picking up radiation from > the radiator. If that physical configuration cannot be avoided, then an > additional common mode choke at the shack entry point can help.
I agree and have done all that. I have a doublet, centre-fed with 300 ohm ladder line dropping vertically to a DX Engineering choke balun (which contains three binocular ferrite chokes in series). For good measure, I have a Fair-Rite #31 clamp-on ferrite on the co-ax next to it. The co-ax then runs in a duct buried about 350mm deep to the house, where it goes up the external wall and then through it about 4m above ground level into the (upstairs) shack, where there's another #31 clamp-on ferrite. > With effective common mode chokes on the antenna and feedline, you > should not have to use ferrites on every cable in the shack Well, my experience disproves your hypothesis. While common-mode current on the feedline is often a problem, it isn't necessarily the only problem. The problem here is radiated RF, not conducted RF, being picked up by the USB cables. It's only to be expected when the shack is in the antenna's near field. 73, Richard G4DYA ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
