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## Re: Topband: My Turn For a Brain Pick - Sanity Check

 To: topband@contesting.com Re: Topband: My Turn For a Brain Pick - Sanity Check Greg - ZL3IX Fri, 07 Jun 2013 15:14:46 +1200 mailto:topband@contesting.com>
 ```Hi Jim, Have you tried measuring the current in the parasitic when connected? 73, Greg, ZL3IX On 2013-06-07 09:29 a.m., Jim Brown wrote: ```I'm building a simple 2-el vertical array for 40M, with one element driven against radials, and a passive reflector with an equal number of radials. NEC predicts 2.7 dBi over lousy ground at 15 degrees, with peak gain of 3.6 dBi at 25 degrees elevation, and F/B of about 8 dB. ``` ```We've got this set up in W6GJB's pasture, roughly 5 miles S of me, with me centered on the main lobe, and I'm looking signal strength with my K3 reading relative dB (and with AGC turned off). Our signal is 35 dB above the noise level with Glen's KX3 at 3 watts. Terrain is hilly between us, and we have 16 radials on both elements. ``` ```We're making three measurements -- with the array as designed, with the reflector shortened by 3 ft (which should make it director) but still connected to the radials, and with the reflector simply insulated from the radial plate. ``` ```What I hope to see if the antenna has the predicted directivity is 3 dB difference between the designed array and the reflector floating, and 6-8 dB difference between the array as designed and reversed. ``` ```What I see instead is the same signal strength for all three configurations within 0.2 dB. So the question is, why? A vertical plot in NEC shows the F/B at all elevation angles, all the way down to 1 degree and up to 80 degrees. ``` 73, Jim K9YC All good topband ops know how to put up a beverage at night. _________________ Topband Reflector `````` All good topband ops know how to put up a beverage at night. _________________ Topband Reflector ```
 Current Thread Topband: My Turn For a Brain Pick - Sanity Check, Jim Brown Re: Topband: My Turn For a Brain Pick - Sanity Check, Greg - ZL3IX <= Re: Topband: My Turn For a Brain Pick - Sanity Check, James Wolf Re: Topband: My Turn For a Brain Pick - Sanity Check, Jim GM Re: Topband: My Turn For a Brain Pick - Sanity Check, Tom W8JI Re: Topband: My Turn For a Brain Pick - Sanity Check, Charlie Cunningham Re: Topband: My Turn For a Brain Pick - Sanity Check, Tom W8JI Re: Topband: My Turn For a Brain Pick - Sanity Check, Charlie Cunningham Re: Topband: My Turn For a Brain Pick - Sanity Check, Rick Kiessig Re: Topband: My Turn For a Brain Pick - Sanity Check, Jim GM Re: Topband: My Turn For a Brain Pick - Sanity Check, Jim GM