The OA-3633() consists of the
AM-2060() Audio Amplifier/Power Supply and the CX-4655
Cable. The "A" version has some extra power supply
filtering, probably to increase it's TEMPEST
rating for use with COMSEC
AM-2060() Audio Amplifier / Power Supply
Radio Sets can be used in
either a man pack (GRC-125, GRC-160) or vehicle (VRC-53,
VRC-64) configuration. When used in the vehicle
configuration the Radio Set is installed into the AM-2060()
Audio Amplifier/Power Supply. TheAM-2060() Audio
Amplifier/Power Supply is installed into the MT-1029 Mount
which provides the 24
Volt DC power input, interface to the VIC-1
Vehicle Inter Communications
system, or COMSEC
equipment like the KY-57
by means of the J-3513 Junction Box.
The AM-1777 looks very much like this, how is it different? Let me know
. One thing is that
the AM-1777 only works with the PRC-77 (it does not have the
low voltages needed for the PRC-25).
The cable connects between the AM-2060 and the Radio
Set. It provides power to the Radio Set and gets the
line level audio from the radio to feed the audio amplifier
and drive the speaker. The CX-4655 comes in either a 9"
or 11" long version. They both have U-316 connectors on
each end since the Radio Set POWER connector is identical to
the AM-2060() Radio Set connector. The cable has all the
pins wired 1:1. Note when this cable is used the DC
vehicle power is fed to the MT-1029
which feeds the AM-2060 Power Supply which in turn feeds the
PRC-25 or PRC-77 radio, therefore the radio's internal battery
is not being used.
Note you can use a couple of my Power Connector Kit (PCK
) to make up a cable since
it's the connector the mates to the POWER connector on the
PRC-25/PRC-77 and the connector on the AM-2060.
The PRC-25 and PRC-77 Radio Sets operate from standard "12
Volt" civilian vehicle DC power, like you would get from a
Cigarette Lighter Socket. They can be powered using the
Adapter or 257477BA Battery Adapter. But when used in a
military vehicle with "24 Volt" power, a power supply is
needed to supply not only the "12 Volt" main power but also
the 2.5 Volt DC for various parts of the PRC-25 (the PRC-77
does not need this supply). The AM-2060 converts the
military vehicle 24 VDC supply to the various voltages needed
by a PRC-25 (or just the 12 V needed by the PRC-77).
Audio Amplifier & Speaker
The background noise level in a military vehicle is higher
than that experienced by a man on foot, so an audio amplifier
and speaker allows the driver and/or passengers to hear the
radio in a hands free manner.
Note that there is no RF connection between the AM-2060 and
the Radio Set or Antenna. There is no RF amplification
involved with the AM-2060. The
contains both an Audio Amplifier/Power Supply and
an RF Power Amplifier for the PRC-68
Family of Squad Radios
The VIC-1 system allows crew members to hear the
radio and in some cases transmit on the radio. In
addition the radio can be interfaced into a retransmission
system either to a radio in the same band or to a radio on
another band. For example a PRC-77
+ AM-2060 + MT-1029 and be
connected to a C-2299 Radio Relay
box and then to a GRC-213
H.F. radio to make a cross band repeater. For this
application the retransmission function is handled by the
AM-2060 and MT-1029, not the AUDIO connector on the PRC-77.
Antenna Band Control
Antenna System uses
the MX-6707 Base Matching Unit which needs to be set for the
frequency band in use. This can be done using the manual
band switch or remotely using electrical signals. These
can come from the RT-246, RT-524
or the AM-2060. The AM-2060() has a band switch on the
front panel that needs to be set for the frequency band that
includes the operating frequency of the Radio Set.
The AM-2060A is located by the MT-1029
using two alignment pins that are a close fit. My
AM-2060A would not go onto the pins until I loosened the nut
on the MT-1029 pin that's on the junction box. I also
applies a film of Radio Shack Lube-Gel to both pins so there
will not be any corrosion.
Order of Cable Connection
I have the radio system indoors, not in a vehicle. It's
best to connect all the cables to the MT-1029 BEFORE adding
the AM2060A and PRC-77. Once you've got all the radio
equipment attached it's more difficult to install the cables
onto the MT-1029.
Rotating Connector Keys
One of the connectors coming from the J-3513 had it's
connector Key rotated from where it needed to be. You
can use pliers to grab the straight knurled sleeve behind the
connector and turn the Key to line up with the equipment.
The MWM type vehicle connectors used for DC power in and out
as well as for the VIC-1 interfaces have recessed nuts and you
need a spanner to remove both nuts so you can slip out and
reinstall the connector proper in at any 45 degree
increment. This is often needed to get the cables to
I got a set of spanner wrenches from Fair Radio and a couple
of them are just the right size for doing this.
TM 11-5820-498-35 DS, GS &
Depot Maint Man Amplifier-Power Supply Groups OA-366()/GRC
This manual is part of the VRC-53/GRC-125
for the PRC-25 and VRC-64/GRC-160
for the PRC-77 -498 series of manuals.
It includes operation with VIC-1 Vehicle
equipment since the AM-2060 interfaces to the
VIC-1 through the MT-1029 Mount