On Thu, Oct 1, 2015 at 12:58 PM, Jim Brown <[email protected]> wrote:
> What these two measures can do for you is CONTROL where common mode > current flows -- it will flow on that new ground wire and that new > dedicated power line -- but that RF current will still RADIATE, and can be > picked up by any other wires in your home, like those in your home > entertainment system. It's even worse, as true what Jim says is. Short version: Common mode current messes up BOTH transmit and receive. Don't buy junk baluns and blockers. Insist on response curves from manufacturer. Never ever go cheep on baluns and blocking. Either buy or make the good stuff. Long version: The common mode path is a two way street. Many find attic antennas very noisy because they hear all the RF noise from all the stuff in the house. Changing to an outside antenna even a little ways from the house reduces that noise immensely. If a common mode path is open, it's an open road from the house to the antenna for house noise. At the antenna the house noise is added to the reception, making it much noisier. A common mode block working well enough to stop TX interference often still hasn't enough blocking to prevent the reverse path from raising your RX noise level. Designing your station to eliminate ground and common mode problems, before installing anything, will save you much consternation in the future. Understand there are companies who advertise in national magazines who sell junk baluns and junk common mode blocking devices. Or they say all-band when they barely cover down to 40 meters, if that. They are sure we are a bunch of dumb clucks who can't possibly tell the difference. Prove them wrong. Caveat Emptor. Buy from manufacturers that publish the response curves, with actual dB values, on all their devices. Ignore everyone else. 73, Guy K2AV ______________________________________________________________ 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 Message delivered to [email protected]
