Well, sometimes, life is the art of the possible. At the time I was living in q small duplex on a corner lot and running a bunch of on-ground radials wasn't an option. Still I was working YBs and DUs etc. on the evening LP on 40m that others weren't even hearing! They'd come up on frequency and send ??? -during and after my qsos. In my experience a vertical 1/2 wave is a very potent antenna because its high current portion is up 1/4 wavelength and it's take-off angle is so low for DX work even without that last 1 dB!! Just like some guy s like to dig in the dirt and bury thousands of feet of radials under their inverted Ls when they could do just as well, or better, with 4 elevated resonant radials. But in the end - "if you believe, no proof is necessary - if you don't believe, no proof is possible". Some people are more taken in by popular opinions than by measurements or modeling!
73, Charlie, K4OTV -----Original Message----- From: Topband [mailto:[email protected]] On Behalf Of Jim Brown Sent: Tuesday, January 07, 2014 1:27 AM To: [email protected] Subject: Re: Topband: Feeding 160M Vertical on 80M On 1/6/2014 10:14 PM, Charlie Cunningham wrote: > No, you don't need any radial field under a vertical 1/2 wave. You'll be > driving a few thousand ohms, so a a few ohms or even 50-100 ohms of ground > resistance won't add any significant loss. A simple ground rod will do fine. Yes, but radials DO help -- a bit. See the ON4UN book. Modeling shows that adding a lot of half-wave radials under a half wave antenna increases signal strength by 0.5 - 1.5 dB at low angles, roughly twice as much at higher angles, the greater improvement for lousy ground. To understand this, we must remember that radials serve TWO functions -- to return the antenna current, and to SHIELD the fields produced by the antenna from lossy earth. That is, of course, a lot of copper for 1 dB. Another common way of feeding a half wave vertical is an autotransformer resonated by parallel capacitance. I've done that, and it worked. 73, Jim K9YC _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband
