[TowerTalk] Need recommendations for a 40-10m. Yagi

john at kk9a.com john at kk9a.com
Sun May 6 14:31:28 EDT 2018

On my OptiBeam 40m antennas there is no swaging, just a bolt that goes
though the element. The square boom mounts to the aluminum plate with a
square u-bolt and it's impossible for the mast to spin. The boom to boom
joints were just a couple of internal plates. I have had no issues with any
of these things but perhaps they are with larger beams. Momobeam uses a
similar square boom except they have slots in the boom for coupling and I
have recently seen one that moved out of alignment. I agree that finding
metric tubing in the US is very difficult.  Since DX Engineering now sells
OptiBeam perhaps they can obtain replacement parts.  I always found OptiBeam
owner, DF2BO to be a pleasure to work with.

John KK9A

Jim Thomson VE7RF wrote:

##  Several folks have had  severe issues with the way  optibeam splices
their square boom sections  together.   I dont like their  boom to mast
assys, it uses  2  x muffler clamps for the mast.  Nobody uses  muffler
clamps for anything these days, esp the types with sheet metal saddles, as
depicted. https://www.dxengineering.com/parts/dbo-ob12-4w-p      JKs
version wont budge or slip on any mast.   Optibeam uses  METRIC  tubing
sizes for the elements..and also the square and also their round booms. 
Unlike  6063-T832,  39 ksi yield strength......  or  6061-T6, which uses  40
ksi yield strength..and both using standard tubing sizes and wall thickness,
METRIC tubing does not telescope with a snug fit.  They make a sloppy fit
and have to be either shimmed, or swaged.... pita.   The deal breaker for
myself is that  METRIC  tubing is a bitch to find in Both Canada..and the
USA.  A buddy finally found one source for metric tubing in the usa....and
it was special order, and expensive.  That may have changed.    So even if
you can find replacement METRIC  tubing in the usa, next up you will have to
get the ends carefully swaged.  Any swaging process has to be done dead one.
Too little or  too much, and you are in trouble..esp if too much.

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