[amsat-bb] Re: Cross Boom
Joe
nss at mwt.net
Thu Apr 23 15:43:28 PDT 2009
Just follow the suggestions on the web page that was suggested and
you'll be fine.
But I am curious as to where did you find the 1.25" fiberglass riod?
Joe
MM wrote:
>
>Thanks for all of the good information.
>
>I am going to rebuild my Sat array this spring (its time for a routine overhaul).
>I have a M2 436CP42UG and the M2 CP22 at opposite ends of a 12’ (1.25”) solid fiberglass pole. I am converting over to a 1.5” sold 14-foot fiberglass pole to give me better clearance for other antennas on the tower.
>Kenpro 5500 AZ/EL
>
>I never liked hanging the coax off the back since is throws off the balance.
>When you slide the U-clamps Backward on the M2 boom to compensate for the coax weight on the back, you end up with the clamps on Thinner section of the Boom.
>
>Based on the theories, if I follow the coax routing and avoid the half or full wave points I may be able to run the coax down the boom?
>
>Would this work on the 70 cm too?
>
>Thanks Miles
>
>
>--- On Thu, 4/23/09, Jim Jerzycke <kq6ea at pacbell.net> wrote:
>
>
>
>>From: Jim Jerzycke <kq6ea at pacbell.net>
>>Subject: [amsat-bb] Re: Cross Boom
>>To: "Jeff Yanko" <wb3jfs at cox.net>, "Joe" <nss at mwt.net>, "Billy Simpkins" <bsimpkins31 at dishmail.net>, "Edward Cole" <kl7uw at acsalaska.net>
>>Cc: amsat-bb at amsat.org
>>Date: Thursday, April 23, 2009, 1:41 AM
>>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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>>
>>
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>>>>>>>>
>>>>>>>>
>>>_______________________________________________
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>>>_______________________________________________
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>>>
>>>>>>Sent via AMSAT-BB at amsat.org. Opinions
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