[IRCA] Corner fed loop: was TP for 24 Jan from Victoria, BC

[Nick Hall-Patch]

At 19:35 1/24/2009, you wrote:

>Ahh...this reminds me of an antenna email you sent me a while back. I have 
>modelled both superloops (cornerfed flags) and conventional flags with EZNEC 
>and according to EZNEC height has very little effect on the patterns. Of 
>course it effects the gain since it means a larger antenna. Bruce Conti's DX 
>using his superloops is extraordinary, IMHO considering his QTH is somewhat 
>inland and that his bearings to the coast to Eur-asia are quite far from the 
>Atlantic, and to me this indicates a really good antenna system.
>
>What might be happening at your sunrise is some tilt in arrival angles and a 
>different response at those angles from the two antennas.
>
>If your domestic rejection isn't so good with the corner-fed loop, perhaps 
>some adjustment of termination would help or just phase it vs the flag ?

Actually the corner fed loop has a vactrol adjustable termination, Neil, so I'm 
always trying to minimize splash as I listen.   But with the Flag, the front to 
back ratio seems to be  broader and deeper overall, meaning that listening is 
less troubled by splatter at most settings of the termination; it's not a 
matter of fine tuning it, and I often leave it at a general setting unless I'm 
really working at digging something out.

I've used EZNEC a bit (I'm no expert, mind you), and found that I can't really 
verify what I've observed in real life with different sized corner fed loops.   
If you can, I'd love to find out how it's done.

best wishes,

Nick




*
Nick Hall-Patch
Victoria, BC
Canada 

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Re: [IRCA] Corner fed loop: was TP for 24 Jan from Victoria, BC

[Chris Knight]

Nick,

I notice the splash, too, with the corner-fed loop, and it does seem
stronger than on my flag. The main advantage I see with a corner-fed loop is
it can null all my locals (no phasing required) when oriented just right. I
heard that a flag is optimized for a real impedance (~950 ohms) with the
imaginary portion (Xc and Xl) at zero due to the center positions of the
feed and termination points. For a corner-fed loop the feedpoint impedance
would have more imaginary component which would have to be tuned out. Even
so the antenna performs really well for this QTH.

Next weekend I'm going to convert the NW Flag over to a corner-fed loop with
dual-termination NW/SE. Hopefully that will be an improvement, if not, an
experiment.

Anniversary "weekend" this weekend so won't get back to DXing/computer until
next week.

73,

Chris Knight
Fort Lupton, CO

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