[MRCA] [MMRCG] AN/PRC-108 Antenna

[John P. Caldwell]

Ray,

I was faced with the same issue last year when I acquired a PRC-108.  I
fabricated an aluminum plate w/ thumb screws that attaches to the upper
right side of the housing (see pics).  The plate holds a machined block of
Delrin that accepts a PRC-77 antenna mounting block.  The assembly lets you
use AT-271 and AB-591 base.  I have a coax lead with a PL-259 wired thru the
Delrin block to the antenna mounting base.  The pictured "A" model can be
rotated by flipping the plate 90 degrees.  Model "B" (in the works now) uses
a knob and can be rotated to any position

 

John

WD8INC

 

From: MMRCG at groups.io [mailto:MMRCG at groups.io] On Behalf Of Ray Fantini
Sent: Tuesday, June 26, 2018 8:57 AM
To: mrca at mailman.qth.net; MMRCG at groups.io; milsurplus at mailman.qth.net
Subject: [MMRCG] AN/PRC-108 Antenna

 

So the question is this, I am in the process of building up some sort of
small whip antenna for my PRC-108 transceiver. It has rocks for both 3.885
and 5.357 installed being it operates on both USB and AM. Happy with the way
it works when used with its 50 Ohm output driving a dipole or inverted V but
the idea now is to have a vertical whip for backpack portable operation over
short distances, things like Dayton or other field events.

The radio has an internal loading coil and second output that can drive a
short antenna but the problem is that I will have to fabricate the adapter
plate, mount and antenna from scratch. I have two choices for the antenna
that I am currently looking at. The first choice is a seven foot whip
antenna but I do not have a base for that antenna yet, and it appears that
it would be a rigid non flexible base if I build one. The second antenna is
just a little over three feet long but has a spring base and good attachment
point. I would prefer to work with the shorter whip being it's mechanically
better and also would avoid some of the issues that the long antenna with
the rigid base may get into.

At the frequencies this radio operates at both antennas would be way short
and I think what the radio originally had was a ten foot whip but the
possibility of finding that is right up there with Hens teeth. Assuming that
any vertical would be a poor compromise would there be any real difference
between using the super short three foot vertical as opposed to the seven
foot vertical? Can anyone model what the difference would be?  

 

Ray F/KA3EKH

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[jcaldwell at rbcos.com]

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