Thanks for the replies and particularly Steve and Peter.
For reasons that are now obscure I never read the second part of the YCCC
article (or if I did immediately forgot it....) and follow the reasoning.
I do have some doubts about how effective the 470uH chokes would be, but they
must provide some isolation and presumably enough. And wonder why my RX 4
square had a good pattern with no common mode choking during the short periods
that the elements were undamaged.
Anyway, thanks again.
73 Roger
VE3ZI
On Thursday, 23 September 2021, 15:34:23 GMT-4, VE6WZ_Steve <ve6wz@shaw.ca>
wrote:
Roger,
Each HI-Z amp (impedance buffer) at each element already has a 1:1 “braid
breaker” choke at the input so is already isolated from the feedline.
The chokes at the combiner prevent all the feedlines together them from acting
like a ground screen. Without the chokes, they are all RF bonded together.
John W1FV explained this in his original NCC paper how it upsets the pattern.
I have thought about redesigning the combiner board with integrated 1:1 toroid
braid-breakers on each feedline (just like the element amps) but haven't got
around to that.
That would be a lot cheaper and easier than installing out-board chokes.
Steve, ve6wz
> On Sep 23, 2021, at 12:50 PM, Roger Parsons via TowerTalk
> <towertalk@contesting.com> wrote:
>
> I have recently completed building a YCCC 9 Circle array, and it seems to
> work quite nicely. This replaces a receive 4 square using top loaded elements
> - I could never get that to last as animals would break one or more of the
> top loading wires mistuning the array.
>
> The instructions for the YCCC array are explicit that there must be common
> mode chokes between each element and the combiner unit. That is obviously a
> good idea, but I can't understand why they suggest putting them at the
> combiner unit end of the feed lines to each element, and my feeling is that
> they should be at the element ends. (The elements have a very poor ground,
> and the feed lines are significantly long. Surely that means that the high
> impedance of a common mode choke at the combiner will be transformed to a
> different and probably lower impedance at the element. The effect of that
> could be that the feed line becomes the main and unpredictable ground for the
> element, and different for each element, which I think is exactly what is not
> required.)
>
> Comments would be appreciated.
>
> 73 Roger
> VE3ZI
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