OK, I see where this is coming into play. So it's possible that the coax shield could react to the feedpoint system and pattern. Now this raises a question. If this is the case, has anybody tried a broadband choke balun to limit this potential problem? If you think about it, the bigger issue with coax effecting the radiation pattern is improper decoupling of the fed point. If the outside shield is hot with RF it will radiated and effect the pattern big time. If the coax is properly decoupled at the fed point the outside shield will ideally have zero rf current on it and ideally have no impact on the pattern.
Thoughts?
73,
Jeff WB3JFS
----- Original Message ----- From: "Jim Jerzycke" [email protected] To: "Joe" [email protected]; "Billy Simpkins" [email protected]; "Jeff Yanko" [email protected] Cc: [email protected] Sent: Wednesday, April 22, 2009 11:09 AM Subject: Re: [amsat-bb] Re: Cross Boom
Because the shield of the coax "looks" like a piece of pipe, and has the same effect on the antenna pattern that you're trying to eliminate by going to a non-metallic cross-boom. Jim KQ6EA
--- On Wed, 4/22/09, Jeff Yanko [email protected] wrote:
From: Jeff Yanko [email protected] Subject: [amsat-bb] Re: Cross Boom To: "Joe" [email protected], "Billy Simpkins" [email protected] Cc: [email protected] Date: Wednesday, April 22, 2009, 10:55 AM Hi all, I found this line confusing....
"But then if you go insulated then do not run the feedline along it either or you just defeated the purpose of the insulated boom."
My question is if you run the coax along an insulated crossboom, ie. fiberglass, how could that affect the coupling of the transmission line when the object it is being attached to is "insulated"?
73,
Jeff WB3JFS
----- Original Message ----- From: "Joe" [email protected] To: "Billy Simpkins" [email protected] Cc: [email protected] Sent: Wednesday, April 22, 2009 7:06 AM Subject: [amsat-bb] Re: Cross Boom
It all depends on how the elements are mounted.
If at 45 to 90 degrees from the crossarm, no propblem
and use anything,
But if in the same plane then need insulated
crossboom,
But then if you go insulated then do not run the
feedline along it
either or you just defeated the purpose of the
insulated boom.
Billy Simpkins wrote:
Is a fiber glass or some other non-conductive
material necessary for a
cross boom? What or the advantages and
disadvantages versus a metal one?
Thanks, Billy KF0CK _______________________________________________ Sent via [email protected]. Opinions expressed are
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