PS Magazine - TB 43-PS-612
PS, The Preventative Maintenance Monthly
ISSUE 612
NOVEMBER 2003
PS 612
NOV 03
41
FHMUX TD-1456/VRC…
T
here’s a love/hate relationship
going on with the frequency
hopping multiplexer (FHMUX).
Some units won’t deploy with-
out the FHMUX. Others don’t
want a thing to do with it!
The reason for the two views
is the garbage being churned
out by the rumor mill.
So let’s set
the record
straight and
maybe every unit
will be sending
their FHMUX a
valentine!
if it
doesn’t
do the
job for
you, write
Half-Mast
and let
him know
why.
The FHMUX
works, so
give it a
chance.
Rumor One
We lose range and power when using the FHMUX.
Okay, it’s true you don’t get the same RF power out of the antenna connector on the
front of the FHMUX as you would at the AM-7238 power amplifier.
But, you do get optimum range and that’s what you’re after! Using multiple active
radios and antennas produces less range than using a FHMUX with a single antenna.
Suppose you’re using four OE-254/GRC antennas located around your command
center. You’re going to get interference and “frequency collisions.” Down goes the
range of your radios. The FHMUX range will be greater with no interference or “col-
lisions”!
Rumor Two
We can only transmit on one radio
at a time through the FHMUX.
Not even an okay, here. This rumor is not
true!
You can receive and transmit on all four
radios at any time through the FHMUX. The
FHMUX switches between radios hundreds of
times per second. The switching is so fast you
won’t know it’s happening.
Rumor Four
FHMUX doesn’t always work.
If the FHMUX does not work, the problem is probably with the cables. You’ve con-
nected them wrong! When the repair guys are called in to troubleshoot, that’s usually
what they find.
Make sure you have the needed FHMUX manuals to get it up and running. You’ll
need: TM 11-5820-890-10-8,
SINCGARS Operator’s Manual;
TM 11-5820-890-23P,
Unit and Direct Support Maintenance Repair Parts and Special Tools List for FHMUX
TD-1456/VRC and Mount MT-6845/VRC;
SB 11-131-2,
Supply Bulletin Vehicular Sets
and Authorized Installations, VOL II, SINCGARS, FHMUX, and EPLRS;
TM 11-5820-
890-30-6,
Direct Support Maintenance Instructions for the TD-1456/VRC Multiplexer.
Rumor Three
The FHMUX can only operate
for up to 24 hours, then it must
be shut down or it will fail.
This is garbage, folks. True,
some early FHMUXs had an over-
heating problem, but that’s ancient
history. Now they can operate until
the cows come home—and leave
again in the morning!
Rumor Five
There is no advantage gained by
using the FHMUX.
That’s a rumor that is way off base. Using
the FHMUX provides several advantages.
1.
The FHMUX reduces your visual target sig-
nature. Fewer antennas means you’re less like-
ly to draw the enemy’s attention. That increas-
es your odds of surviving on the battlefield and
that’s an advantage you definitely want.
2.
The FHMUX has improved radio range. The
use of the FHMUX and one antenna reduces
the interference and frequency collisions that
degrade your radio net ranges.
3.
The FHMUX reduces setup and takedown
time. A unit takes about two hours to erect four
OE-254 antennas and about 30 minutes to set
up the one OE-254 antenna using the FHMUX.
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