Re: [IRCA] [NRC-AM] DKAZ Antenna

[Chuck Hutton <charlesh3@xxxxxxx>]

Modelling numbers for a 20 x 140 DKAZ to back up what I said:    - best null is -42 dB and the -6 dB null width is 72 degrees.    - lower the termination by 80 Ohms and the best null (straight off the back) is only -29 dB but the 6 dB null width jumps up to 106 degrees.
Chuck

From: charlesh3@xxxxxxx
To: irca@xxxxxxxxxxxxxxxx
Subject: RE: [IRCA] [NRC-AM]  DKAZ Antenna
Date: Fri, 21 Aug 2015 21:41:51 +0000




This is a repeat of my earlier comment to Nick, where I guessed / thought that the minima does not really move.
Ad I see it, the issue here is that the best null is the sharpest (narrowest) null. If you want a null to cover something off to the side a bit, you can indeed "mis-terminate" and get a wider null that hits the off-to-the-side station. The price you pay is a degraded null in the backwards direction.
The way to prove this is to record termination and signal strength data for someone directly in the null and someone off to the side. That's tough to do from Grayland is you choose to face the antenna  west for DX - there are  few stations directly in the eastward null. Unfortunately for testing purposes, it would be better to face the antenna SW or SSW.
Chuck

 		 	   		   		 	   		  
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