All
" 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. "
Those papers can be find het PI4CC Contest Club
<https://www.pi4cc.nl/tech-info/rx-array/>
Peter
-------- Doorgestuurd bericht --------
Onderwerp: Re: [TowerTalk] YCCC 9 Circle Receive Array
Datum: Thu, 23 Sep 2021 13:34:21 -0600
Van: VE6WZ_Steve <ve6wz@shaw.ca>
Aan: Roger Parsons <ve3zi@yahoo.com>
CC: Tower and HF Antenna Construction Topics. <towertalk@contesting.com>
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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|