[amsat-bb] Re: Cross Boom

Wed Apr 22 22:41:42 PDT 2009

It's here on Howard's site:
http://www.g6lvb.com/fibermetalboom.htm


--- On Wed, 4/22/09, Edward Cole <kl7uw at acsalaska.net> wrote:

> From: Edward Cole <kl7uw at acsalaska.net>
> Subject: Re: [amsat-bb] Re: Cross Boom
> To: "Jeff Yanko" <wb3jfs at cox.net>, kq6ea at pacbell.net, "Joe" <nss at mwt.net>, "Billy Simpkins" <bsimpkins31 at dishmail.net>
> Cc: amsat-bb at amsat.org
> Date: Wednesday, April 22, 2009, 10:39 PM
> The coax shield coming off the antenna boom at a right angle
> looks 
> like another parasitic element being added to the antenna
> causing 
> severe distortion of the antenna pattern.  But if one
> installs the 
> antenna in the X configuration and attach the cross boom in
> a 
> location away from any of the elements one can tightly run
> the coax 
> across the metallic cross boom with little effect.  This
> was tested 
> by WA5VJB and is a published article.
> 
> I have my M2 436CP42UG mounted in this fashion and it
> preforms well.
> 
> 73, Ed - KL7UW
> maybe someone else can point to the link to that article.
> 
> At 11:41 AM 4/22/2009, Jeff Yanko wrote:
> >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"
> <kq6ea at pacbell.net>
> >To: "Joe" <nss at mwt.net>; "Billy
> Simpkins" <bsimpkins31 at dishmail.net>; "Jeff
> >Yanko" <wb3jfs at cox.net>
> >Cc: <amsat-bb at amsat.org>
> >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
> <wb3jfs at cox.net> wrote:
> > >
> > >> From: Jeff Yanko <wb3jfs at cox.net>
> > >> Subject: [amsat-bb] Re: Cross Boom
> > >> To: "Joe" <nss at mwt.net>,
> "Billy Simpkins" <bsimpkins31 at dishmail.net>
> > >> Cc: amsat-bb at amsat.org
> > >> 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" <nss at mwt.net>
> > >> To: "Billy Simpkins"
> > >> <bsimpkins31 at dishmail.net>
> > >> Cc: <amsat-bb at amsat.org>
> > >> 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
> > >>
> >>_______________________________________________
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> > >> >>
> > >> >>
> > >> >>
> > >> >
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