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

[Nick Hall-Patch <nhp@xxxxxxxx>]

At the risk of alienating many subscribers to the group if we go on 
much longer with this....I suspect we all need to get together for an 
EZNEC-chopping session Chuck.  Neil and you have a lot of experience 
with the program, and I'd really like to learn what you both do to 
get the results you get.  Arrival angles? (and the resultant loss off 
the front end with lower arrival angles) Actual termination 
resistance values?  (field results usually say 900 ohms or less; is 
that what is being used in the model?)  Frequency?

I just find that I can find pretty much what I want to find with 
EZNEC at some arrival angle or another, and particularly by looking 
at vertical polarization or other tweaks, and that way madness lies, 
at least for those of us with little brain.

Enlightenment may come with some table pounding and laptops at 2 paces, hi.

In the meantime, I'll adjust my termination if I can while I DX....if 
only to tone down some Grayland lowband noise.   But I like these 
antennas because they generally knock down domestics for a coastal 
DXer, even if sometimes the termination isn't always adjusted for the 
deepest and sharpest null.  That is especially, as you point out, if 
one has set up the antenna so that there isn't exactly anything there 
to null with that deepest and sharpest null.  KELA-1470 wasn't my 
biggest problem at Grayland by a long way.

best wishes,

Nick




At 22:01 21-08-15, you wrote:
> 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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