AM-7148/GRC-206 HF RF Amplifier NSN 5985-01-149-1437
© Brooke Clarke 2008
Non User Friendly Military
This is the 150 Watt RF Amp covering
2 to 29.9999 MHz used to make a URC-113
radio which is used in the GRC-206
Program Pacer Speak. It arrived with other GRC-206 system
components still sealed in the military packaging, so it's New Old
|| The Label says:
FSCM 37695 P/N 566084-806
FSCM 37965 P/N 5985-01-149-1437
H. F. POWER AMPLIFIER/ANTENNA COUPLER
SERIAL NO 882
The packing bag is marked MAY 1986.
A stamp on the bag:
FT WAYNE, IN
P100 A2530 3 87
117E, T/I, C/E, S/1
If you know what this means let
DATE OF MFG 1089 MIL-P-130F TYPEII
Inside duct tape was applied to the amplifier in many
places and will take some cleaning to remove the sticky
|The BITE connector is a 6
socket mil connector.
The Injection connector needs more
research. May be for 3.6 MHz signal for BITE, but it's
still not clear.
The 50 Ohm connector is for test purposes.
The high power RF only comes out of antenna coupler High
Voltage terminal on the rear panel.
The yellow cap is on the interface connector to the
RT-1209A, RT-1209B or the RT-1444 connected on the back of
|I didn't expect the fan.
|The power connector J6 is the
common 4 pin military vehicle DC
The antenna coupler is designed to load military whips like
the AT-1011 or AS-2259.
The connection between the HV terminal and the base of the
antenna should be a plain HV rated wire (not coax) and as
short as possible.
Since there's only one DC power connector this must be the
last equipment in the military vehicle chain of DC power.
J1 of the AM-7148 connects to the RT-1209() Power Amp/Antenna
Connector. The signals on this connector include the RF
exciter output/receiver input, the frequency in MHz (6 bits),
various control signals related to tuning the antenna, a frequency
standard and DC power to the RT-1209().
So this Amp/Ant Coupler could be used with a stock RT-1209 where you
would control the radio via the RT-1209 front panel.
Note the latch connector at the right of the photo is not hooked to
the RT-1209, but the connector between the RT and Amp combined with
the latch at the left rear anchor the RT. When the RT-1444 is
inserted between the RT-1209 front panel and the main chassis the
front panel will move forward and the right latch will engage.
It's interesting that the designers allowed this use of the AM-7148.
The audio cable connects between the lower RT audio jack and the
AM-7148, but is too short to do that on the setup shown at left.
Still TBD are the frequency standard details. It's most likley
a 5 MHz input that can come from the O-1814 RFO.
The AM-7148 audio connector J5 connects to one of the audio
connectors on the RT-1209 and that's where the AM-7148 gets the
receive audio to drive the speaker. But there is no squelch in
the AM-7148 only has an OFF-Volume control.
|BITE (A: BITE Fault, B:
notTxRdy, C&D: Gnd)
|50 Ohm Ant
|Freq Std INJECTION
|DC Pwr (B=+27.5 V,
A&C=Gnd) Rx 1Amp, Tx 19 Amp
|HV Antenna Terminal (missing
The RT-1209 uses a 5 MHz reference oscillator for the frequency
synthesizer and I'm guessing that the Freq Std INJECTION jack on the
AM-7148 expects a 5 MHz reference sine wave at about 0 dBm.
BUT, the O-1814 RFO has a 5 MHz reference frequency output and so is
compatible with the needs of the RT-1209. Seems strange it's
Both the AM-1748/GRC-206 and the O-1814/GRC-206 were designed for
the GRC-206 system so there must be a reason that they are not using
a coax to connect the O-1814 5 MHz output to the AM-7148 5 MHz
input. If you know please tell me
Packaged with the AM-7148 is an audio cable that's very short and
formed into a "U" shape to take the Rx audio from the RT and feed it
to the audio amp and speaker.
p/n 566084-806 10/87.
Non User Friendly Military Names
When I received this system there was an outer box
containing a number of cables and in that box was another
FSCM 37695 P/N 566084-806
(and a more information below
like the NSN, contract number,
etc that I didn't read.
Emailed the seller and asked if the AM-7148 was being
shipped in separate box. Phone reply was it was in
box with cables. Sure enough, the box labeled as
CABLE, AUDIO also shows on the label that it contains the
AM-7148. Maybe the order of the two items was
alphabetical, but it would be much better to have done it
in order of importance.
I've heard that very expensive military radio systems have
been surplussed with a lot title like AUDIO CABLE or an
equivalent and the buyer gets the lot for a song.
The RT-1444 is an add on to the
RT-1209 (no letter) that allows remote control of the radio.
The connector on the side of the RT-1444 mates with J10 on the
C11169/GRC-206 Signal Distribution Unit via a cable.
When the RT-1209 is the A, B or C version the system cable mates to
the front panel connector on the RT and an audio "Y" cable is needed
if the speaker in the AM-7148 will be used.
The AM-7148 has a voltage limiting circuit that will regulate 28 to
30 VDC inputs to 27 VDC outputs, but if the input goes lower than 28
this circuit is non operational. There is no switching mode
power supply. So to get max RF power out the input DC needs to
be at least 28 VDC. The test specs say 100 Watts out min and
that may be at the minimum input of 18 VDC below which the low
voltage cutout disconnects the input.
The AM-7152 should work in this
system. It's just a squelch box and so could be connected in
series with the Audio from the RT to the AM-7148.
TO 31R2-2GRC206-22 Maintenance Instruction with Illustrated Parts
Breakdown, Depot, Amplifier-Coupler, AM-7148/GRC-206, NSN
TO 31R2-2GRC206-6WC-1 PM Inspection Work Cards
Chapter 2 Installation refers to TO
31R2-2GRC206-2 and there is no Operation chapter.
TO 31R2-2GRC206-2 Radio Communication System
AN/GRC-206(V)1 Immediate Maintenance w/IPB
TO 31R2-2GRC206-12 Radio Communication System AN/GRC-206(V)1
and (V)2 Depot Maintenance w/IPB
Nerds for some GRC-206 manuals.
The GRC-206 system is on the PRC-104
The GRC-206 system components are also linked from the MT-6250
equipment rack (Mount) page.
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