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Re: [IRCA] [NRC-AM] DKAZ Antenna
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
> From: Mark4@xxxxxxxxxxxxxxx
> To: am@xxxxxxxxxxx; irca@xxxxxxxxxxxxxxxx; MDXC@xxxxxxxxxxxxxxx; mikegjco@xxxxxxxxx; FredB@xxxxxxxxxx
> Date: Fri, 21 Aug 2015 15:49:59 -0500
> Subject: Re: [IRCA] [NRC-AM] DKAZ Antenna
>
> So is the minima actually moving or is the rear-response beamwidth changing?
> Or is that the same thing? And Nick: (especially in your 1640/1680
> example), might there be some skywave in the mix? Makes an Old Novice
> wonder...
>
> KAZ YOUR THOUGHTS ??? ALSO...SEE LAST PARAGRAPH BELOW
>
>
> Mark Durenberger, in search of better understanding
>
>
>
> >-----Original Message----- From: Nick Hall-Patch
> >
> >>NICK 1: I haven't had experience with two D-Kaz Mark, but do I gather then
> >>that you haven't seen evidence of null steering with the DKaz alone? MARK
> >>1: I HAVEN'T SEEN EVIDENCE OF STEERING, JUST DEPTH ADJUSTMENT (PRESUMABLY
> >>INCLUDING RE-SHAPING OF SIDE-LOBES). MARK 2: AND I COULD BE WRONG ABOUT
> >>THIS.
>
> NICK 2: I'm not sure my use of "null steering" is entirely the correct
> term, even for the Flag. The direction for minimum signal response moves
> with adjustment of the termination (especially for vertical polarization),
> but the depth of the null is not ( ) as great as the best null obtained
> directly off the back of the antenna. MARK 2: NICK, I'M NOT CERTAIN THIS
> IS PROVED. DATA! MORE DATA!!!
>
> >>NICK 1: I had observed similar (and <900 ohms) termination values for
> >>Portland on 1190 and Seattle on 1000, one 50 degrees off the back of the
> >>antenna, one 30 degrees, but realize that although Portland on 620 and and
> >>Seattle on 710 also had similar values of termination, that value was
> >>higher. And to throw it all out, Portland area on1640 and Seattle on
> >>different values of termination altogether.
>
> > NICK 1: Now I think of it however, doesn't the fact that 1640 and 1680 had
> > different termination resistances for best nulls show a type of "null
> > steering" (or ?). In both cases, the null was around -25dB, and the
> > difference in termination resistance was a couple of hundred ohms. MARK
> > 2: WOW THAT'S A LOT OF CHANGE.
>
> . NICK 1: I had no reference right off the back of the antenna at those
> frequencies, but I assume that both values of termination resistance
> couldn't have each been appropriate for the deepest null off the back of the
> antenna.
>
> MARK 2: I MAY HAVE A LOT OF FIELD TIME NEXT WEEK AND CAN TAKE MEASUREMENTS
> FROM 280 DEGREES AND FROM 325 DEGREES. CAN YOU SUGGEST A SERIES OF
> MEASUREMENTS THAT MIGHT MOVE OUR DISCUSSION FORWARD?DX
>
> best wishes,
>
> Nick
>
>
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