Gary,
Yes, many of us believe that having a metaling cross boom, boom or clamps has no significant effect on your Yagi, actually for most purposes I fully agree it is generally not noticeable.
Being a purist, I wish to state that theoretically any metal part within the antenna except the active element, including boom, clamps etc... affect the antenna theoretical performance. This is why I am presently building a UHF 4 x 30 ele. cross pol LFA Yagis array and a VHF 22 ele. cross pol VHF yagi. These antennas will have no metal parts except the active elements and the purpose is to be prepared or the future Lunar and eventually Mars repeaters, but also for own experimentation. All this not really require fo LEO’s anyway.
For info: when I started to study the LFA’s which is actually a superb concept and I already build a few to test same, with success using fiberglass booms. Originally when I contacted the supposed “inventor” which is inviting the OM’s to contact him for help on his Web site, it was frustrating as unfortunately he was too busy “making a living” thus did not help at all. Actually a blessing in disguise as thus I reversed engineered his design using the appropriate softwares and found many flaws in his claims (probably driven by commercial consideration), such as the metal boom having no effect, element support, worse his proposal for cross pol Yagis totally wrong conceptually, etc… In a nutshell the theoretical conclusion is that having no metal part in the LFA design will make a even better antenna that the “inventor” claims particularly for space com and low signal or in noisy QTH. The acid test will be done in a few months when all this will be on the roof here.
I already suggested a way to do cheap fiberglass booms and forgot to say that paint roller extension is also a cheap way to make fiberglass booms, just ensure that you have aluminium tube on the parts where you will clamps same secure some epoxy glue so that clamps do not crush it.
73
Jean Marc (3B8DU)
On Nov 25, 2020, at 7:03 AM, Gary via AMSAT-BB amsat-bb@amsat.org wrote:
Don't dismiss using a metal cross-boom. People say it won't work without actually examining the problem. When antenna guru Kent Britain, WA5VJB looked at the problem he found a metal boom to work quite well. He then tested it on the antenna range and verified it worked. You can see the paper he presented at an AMSAT symposium here: http://www.kk0sd.net/metalboom/metalboom.htm
When I had a permanent satellite station I used a metal cross-boom, and there were several others in the OSCAR-13 and AO-40 era that did.
73, Gary "Joe", kk0sd
-----Original Message----- From: AMSAT-BB amsat-bb-bounces@amsat.org On Behalf Of Tony via AMSAT-BB Sent: Tuesday, November 24, 2020 6:00 PM To: AMSAT-BB amsat-bb@amsat.org Subject: [amsat-bb] Fiberglass Cross-boom Alternative?
All:
Is there a cheaper non-metallic alternative to fiberglass cross booms? Or maybe a wholesale fiberglass rod distributor that has such a beast at a reasonable price?
Tony -K2MO
Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb