[Milsurplus] MS-44 Mast Sections Used As a Vertical Antenna

[James M. Walker]

Huumm,
A few observations follow:----

----- Original Message ----- 
From: "Paul Alexander" <paul.alexander10 at gmail.com>
To: <milsurplus at mailman.qth.net>
Sent: Sunday, July 16, 2006 6:54 PM
Subject: [Milsurplus] MS-44 Mast Sections Used As a Vertical Antenna

> I have a mast made of MS-44 sections, which as best I can determine is
> part of the GRA-4 antenna system.  The mast sections are thick walled
> aluminum about 45 inches long and 1-3/4 inch OD.  A slip joint is
> formed by an additional 4 or 5 inches of a machined slip coupling in
> the end of each section.  Please note that these are not the thin
> walled aluminum with swaged couplings that are often seen.

That so far seems correct, the description is correct for the support used 
as
PART of the AN/GRA-4 system (*) but you left something out.

>
> This mast was design to support a wire antenna, such as a dipole or
> similar.  As such, the mast is not designed to have RF flowing through
> the mast sections and the couplings between sections are somewhat
> loose.  Whatever electrical connection that exists between sections is
> likely quite intermittent and noisy.

Not quite correct there, though! Several mast systems are available, the one
you are describing supports a dipole or long-wire antenna system, however
it also can act as a vertical, base fed antenna all alone, or a multiple 
system
of a 47 foot vertical, with inverted vee type antennas supported from the
top guy ring. also as combinations thereof.

>
> My question is:  Has anybody found a way to make a firm electrical
> connection between the mast sections that would allow the use of this
> mast as a vertical antenna?  I need to change my antenna configuration
> from a dipole to a vertical and would like to use this mast as it is a
> very well made unit.

Yes first you will need a socket extension, and ratchet to remove the prongs
inside the bottom end of the mast sections, then expand the prongs if they
have been deformed with use, (new ones are not a problem. Re-assemble the
sections, laying on the ground and check for continuity end to end while
assembled. I use the AN/GRA-4 system as a vertical and a support. Driving
the base with the (base insulator installed) using a spare BC-939 tuner and
a good ground rod (8 ft) at the base it workes fine from 2.0 to around 29 
Mhz.
There are a few tricks to using this system effectively. One is to have lots 
of room
and set up a steer-able vertical system with relays for directional 
steering.

As always your mileage may vary.
If you would like the manuals on the system, I have them in PDF and can
email them to you.

Jim
WB2FCN
http://eshop1.chem.buffalo.edu



>
> Any suggestions would be appreciated.  Thank-you!
>
> Paul Alexander
> WB9IPA
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