[amsat-bb] Attaching the coax to antenna boom

[Edward R Cole]

Gentlemen Guessing either you did not read the entire article By 
Kent-AWA5VJB, or misunderstood.

Kent was addressing a way to use a metallic crossboom with crossed 
yagis.  For satellite I suspect you have them connected to produce 
circular polarity.
Normal installation would require the end parts of the crossboom be 
non-metallic (probably fiberglass for strength).  No metal should be 
closer than half-wavelength from element ends.  So the only way to 
dress cable from the driven elements is draped off the backend of the 
antenna booms.

But Kent rigorously measured the effect of a metallic crossboom 
connection to the x-yagi boom to determine least interaction.  The 
connection location on the antenna boom is critical but does allow 
running coax across both crossboom and antenna boom.

Being "cheap and Lazy" I decided to mount my satellite antenna using 
a metal crossboom with Yaesu B5400 azel rotator.  I run my cables on 
the boom with tight corners to  keep cables close to surface on the 
booms.  Everything works well.  I've not made field measurements so 
do not know how well they are working but was good enough for AO40, 
modes US and LS.
http://www.kl7uw.com/sat.htm

Not currently RV for satellite.

73, Ed - KL7UW
--------------------------------------
From: "Frank Karnauskas" <n1uw at gokarns.com>
To: <amsat-bb at amsat.org>
Subject: Re: [amsat-bb] Attaching the coax to antenna boom
Message-ID: <000001d4dd4a$f11aa280$d34fe780$@gokarns.com>
Content-Type: text/plain;       charset="us-ascii"

This is quite curious.

Page 1 of the WA5VJB paper says, "Run the coax back down the antenna
and along the boom keeping the radius small..."  His hand-drawn
illustration shows the feedline going down the boom then making a hard
turn at the boom-to-cross arm plate.

The M2 instruction sheets for the 2MCP8A and 436CP16 antennas both
state (in bold type), "Do not route feedline to boom to mast plate  as
exiting antenna here will adversely affect circular field."

Mr. Britain's paper is obviously focused on mounting the cross bar
somewhere along the boom of a somewhat long antenna.  The M2
instructions are for mounting short antennas from the back of the boom
to the cross bar. Not the same situation.  But, for a newbie like me,
the definitive conclusion to this discussion is...I am still confused.

I was hoping to hang my M2 LEO antennas Monday morning but now not
until after I call the M2 support line for their read on this.

73,
Frank

FRANK W. KARNAUSKAS, N1UW


73, Ed - KL7UW
   http://www.kl7uw.com
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