[Milsurplus] M151 radio instalation

[Bill Carns]

My First thought is that, if you use the local buss point and Single Cable
to the Battery Compartment concept, you open yourself up to inducing
transient drops on the common buss cable when you go to transmit mode with
the high power unit.  The military probably would have liked a common buss
too, but there is some reason they did not do that..  It is also "best
practice" to home run all main DC runs to the battery when doing any
commercial or mobile install now - for the same reason.

 

Bill

 

From: Milsurplus [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of
Ray Fantini
Sent: Friday, January 29, 2016 8:44 AM
To: mrca at mailman.qth.net; milsurplus at mailman.qth.net
Subject: [Milsurplus] M151 radio instalation

 

The DC question: I am in the process of loading down the back of my M151A1
with an AN/GRC-106 and a URC-110 the 106 is mounted one on top the other on
the driver's side and the URC is mounted over on the passenger's side where
you would usually find a VRC-12 installation. I figure that everyone who
owns a M151 has a VRC-12 stuffed into it so I decided not to go that route
and am doing the huge HF/SSB and VHF/UHF installations. After much time and
research I finally have all the shock mounts, mounting plates and all that
sort of stuff finished and am now at the point of having to work out primary
DC connections for the radios. The URC base has a signal four pin power
cable that's appears to me to be identical to what's used in the VRC-12
installation and without the amplifier will only be drawing a couple amps in
transmit at the most but the 106 will suck down around thirty to thirty five
amps in transmit and several amps in standby. The RT-662 receiver exciter is
fairly efficient drawing maybe over two amps in receive and the AM-3349 is
under ten in standby so the current drains are not that bad when not
transmitting. The receiver exciter and the amplifier both have their own
power cables. So in review I will have three power cables, two that will be
under ten amps normal service and one that will be under forty amps in
transmit only.  The GRC-106 installation paperwork for the M151 shows
running both DC cables across the back deck in a channel that I don't have
yet directly to the battery compartment and I figure the URC cable can run
to that compartment also. There are already holes in to the tool compartment
and then to the battery compartment that have been provided but the question
is should I instead bring all the power cables together to a central tie
point somewhere around the radios and then extend just one huge cable to the
battery? Or maybe have a box with circuit breakers in it where they can be
isolated at that point? Was thinking of something like the MX-7777 but from
what I read that was never used on the M151 and was intended for vehicles
where they had issues with transient voltages or spikes. Or do I just extend
everything directly to the batteries like the book shows? Problem with this
is I will end up with the original battery cable and three others now in the
battery compartment and being that I am also looking for the 60 amp
alternator to replace my stock 25 that will be another cable entering into
that aria, by the way if anyone has a sixty they want to sell let me know.
The thing I keep thinking of is if I should have a master disconnect switch
for all the radio equipment or maybe a contactor to isolate everything? Or
just do the install the way the government designed it? Any thought or ideas
welcome.

 

Ray F/KA3EKH

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