PRC-6725 (PRC-139)

© Brooke Clarke, N6GCE 2001 - 2010

Background
Company Name
Warning
Analysis
Battery
Manuals
Parts List
Accessories
    MA 6941 PC programming cable
    Fill Cable
    Clone Cable
    OZ-69 Vehicle Adapter
PRC-152 Battery
Thales DL123 Battery Holder
Links

Top w/Labels
 
Top
 


1 m Ant
PTT
                    side
Back
Conn
                    Side
Inside
Front Inside
Module
Ant Base
 
Bot Batt Conn




Ant Match

Top of batt






Bot of Batt



Prog
                    Cable
MA6941
                PCB

Background

Racal developed the PRC-139 family of military squad radios that are the next generation after the PRC-68 series of radios.  The Air Force Scope Shield II program uses the PRC-139 radio family.  The Scope Shield I program was based on the magnavox PRC-128 radio family.
These use a replaceable module concept to allow three different frequency bands of operation.
  • T suffix for Tactical band of 30 to 88 MHz - 12.5 kHz steps
  • H suffix for High band 136-174 MHz - 12.5 kHz steps
  • U suffix for UHF band 403-470 MHz - 12.5 kHz steps
  • Note 1: CTCSS tones are: 100.0, 103.5, 107.2, 110.9, 114.8, 118.8, 123.0, 127.3, 131.8, 136.5, 141.3, 146.2, 150.0 (30 - 88 MHz only), 151.4, 156.7, 162.2, 167.9, no tone.  Lower frequencies like 94.8 or higher frequencies like 107.2 are NOT available.

    Note 2: the frequency step size is 12.5 kHz for all bands.  So not all repeater frequencies can be programmed.

    Note 3: Carrier squelch can be set for 6, 8, 10, 12, 14 or 16 dB.
    For each band a different antenna is used.  Other options are: There are also a number of variations, for example radios sold with just a single band module, different colors, US Type 1, VINSON Compatible or Exportable Digital Encryption, etc.  The PRC-6725E is a single band (one of the above three) radio with Keypad, Graphics Display (better than an alphanumeric LCD) and built in Speaker-Microphone. It can be fitted with US Type 1 COMSEC, Exportable Digital Encryption or unencrypted.

    In addition to the radios themselves there are accessories like vehicle adapters, and repeater packages in addition to the smaller accessories.

    Company Name

    "Thales Communications has been in existence since the early 1960ís. The company was incorporated as Racal Communications in 1964. In 2000, Racal became part of Thomson-CSF, and, in 2001, as part of a global change, our company's name became Thales Communications, Inc."

    The PRC-139 has been replaced by the Multiband Inter/Intra Team Radio (MBITR) AN/PRC-148(V)1(C) and AN/PRC-148(V)2(C)

    Warning

    There are a number of Racal PRC-139 and PRC-6725 radios out there that have no keyboard, display, built-in microphone or speaker.
    These are not of much use without a computer programming adapter and external handset. Maybe they were made for repeater use?
    They are not very human friendly.

    Photos

    Front - This PRC-6725 has neither keypad nor LCD display, it can only be programed using an accessory.
                There appears to be no Speaker/Microphone built in, like this was a radio designed for a non human use like a repeater.
    Back - just the label
    Right - PPT switch, ? switch and instructions?
    Left - interface connector used for a true "jerk and run" vehicular mount and other tasks like use in a repeater
    Top - Scan switch to watch all the programmed channels, standard 6 pin U-229 style military audio connector, ? antenna connector, Zeroize, A, B, C or D crypto key and Clear switch, 1 through 14 channel selector, OFF-Volume control.
    Bottom - NiCAD battery

    Analysis

    The front cover is held on using Torx-7 screws (American Vermont 15349 bit) while the back/RF module is held by Pozi Drive #1 screws.
    On the front side of the main PCB there is a Max232EWE 9 pin IC.  This is a TTL to RS-232 level shifter.  But why is it here because the PC programming cable has a small PCB inside the DB-9(f) connector that goes to the computer.  I would expect that the cable both shifts the computers RS-232 levels to TTL and also has some pull up and/or down resistors controlled by some transistors.  If the cable is supplying TTL to the radio then why does the radio have a level shifter chip, unless it's to provide ESD protection?

    Digital I/O

    With the radio off Audio pin F is at 2.38 Volts and goes to + 10.4 V when the radio is on.  This pin has no digital data.

    AUDIO pin E has digital data when the radio is turned on that lasts for 13 ms and during operations with the MA6941. The levels are between 0 and 9.8 Volts.
    Timing: 50 uS@0V, 180 uS @ +10, 180 uS @0V, 50 uStrying to get to +10 but only gets to +8.4 (this may be due to the use of the audio test adapter between the MA6941 cable and the PRC-6725).

    If a standard 5 wire audio test adapter is used between the MA6941 cable and the radio, the digital up/download software hangs.  The "F" pin must be some kind of signal and/or handshake signifying it's OK to use digital coms.  The 6 wire audio test adapter is needed.

    Antenna Matching

    Note that the external components used for the antenna system will vary depending on which RF module (frequency band) is installed in the radio.  This 6725 has the 30 - 88 MHz module insalled.

    Battery

    Although the battery on my unit only has Racal markings, I think the BB-521 may be a generic battery for this radio, the PRC-139 and probably other radios that use the twist on type battery.

    9.6 Volts nominal (8 rechargeable cells at 1.2 volts each discharged) with a max fully charged voltage of 12.8 Volts (1.6 Volts/cell)

    BA-5590 to PRC-148 Power Cable

    BA-5590 to PRC-148
          Power Cable
    Note this radio adapter had three center contacts whereas the PRC-6725 only has one.
    I wonder if this cable is backwards compatible?

    Manuals

    Operator's manual for the radio (TM(O) PRC6725)
    Depot level manual (TO31R2-2PRC139-3)

    "Scope Shield II Radio System Notes
    Technical Orders (TOs)
    Scope Shield II Radio System does not come with Operational and Maintenance Instructions.  The TOs are available and should be ordered by following the normal TO ordering procedures outlined in TO 00-5-2 (Technical OrderDistribution System), Chapter 5. 
    The Scope Shield TOs consist of the following:

    TO 31R2-2PRC139-1:  Operational and Maintenance Instructions with Illustrated Parts Breakout (IPB),
        Radio Set AN/PRC-139(C) Hand Held Radio, including Receiver-Transmitter Set,Radio RT-1695/TRC-199,
        Receiver-Transmitter Set, Radio RT-1696/U(C),
        Programmer Unit, Frequency Radio MX-11531/U (Frequency FillDevice),
        Battery Chargers, and Battery Reconditioner. 
        Changes 1 and 2 have been issued and are dated 10 Aug 94 and 15 Mar 95, respectively.

    TO 31R2-4-1085-1:  Operation and Maintenance Instructions with IPB,
        Adapter Group, Radio OF-228/U (Vehicle Adapter).  Change 1 was issued on10 Aug 94.

    TO 31R2-2TRC199-1:  Operation and Maintenance Instructions with IPB, Radio Set AN/TRC-199 (Tactical Repeater).  Change 1 wasissued on 10 Aug 94. 

    TO 31R2-2GRC238-1:  Operation and Maintenance Instructions with IPB, Radio Set, AN/GRC-238 (Base Station).  Change 1 was issued on 10 Aug 94.

    TO 31R2-2PRC139-06:  Work Unit Code Manual

    Training Aids (Tapes)

    Three Scope Shield II training tapes (PIN Number 611901) covering operator and maintenance tasks are available.  These training tapes werere produced and distributed by the Air Force Media Center.  The training tapes may be ordered by faxing a request to the Joint Visual Information Center:"

    Parts List

    Description
    NSN
    Figure
    Item
    CAGE
    Part No.
    PRC-6725 Radio       23386  
    Tactical band 30 - 88 MHz module       23386  
    High band 136-174 MHz module       23386 SS-4100821-501
    UHF band 403-470 MHz module       23386 SS-4100822-501
    Tactical antenna          
    High band antenna          
    UHF antenna          
    Carry pouch          
    Operator's manual         TM(O) PRC6725
    depot level manual         TO31R2-2PRC139-3
    cloning cable        23386 SS-3500272-501
    PC Programmer        23386 MA6941D
    NiCad battery  6140-01-368-8285     23386 SS-1600350-1
    non rechargeable Lithium Battery       23386 SS-1600351-1
    Single Cell Battery Charger       23386 SS-4100846-501
    Multiple Station Battery Charger       23386 SS-4100885-501
    Battery Reconditioner       23386 R2000

    Accessories :

    OZ-69 Mobile amplifier
    Cloning Cable - for radio to radio cloning side multipin connector on one end and U-229 type on other end.

    GC-329 [Slave HRR] - [23386 Assy, SS-3500272-501] - [Master HHR] - 19 Contacts
    Racal Cloning
                  Cable
    Fill Cable

    GC-329 [Keyfill Device] - [23306 Assy, ON606879, SS-3500280-501] - HHR] -19 Contacts
    Racal Fill Cable
    MX-11531/U Frequency Fill Device - a keyboard is part of this device


    MA 6941 PC programming cable - allows a laptop to program the frequencies and other variables such as Receive Frequency, Transmit Frequency, CTCSS Squelch Tones, Data/Crypto Clock Speed, Bandwidth, Transmit Time-out, Radio Zeroize, Scan, Internal Speaker Off, Squelch Level, Cloning Mode, Display Timer, Display Intensity

    Programming Service

    By prior arrangement I will program your 6725 radio for a $15 fee.. You need to pay shipping both ways.

    Important

    Please be sure your new setup is compatible with what the radio can do.  The radio can NOT be programmed to smaller frequency steps than 12.5 kHz or to non supported CTCSS tones.

    • The frequency step size is 12.5 kHz for all three bands, no exceptions.
    • The CTCSS tones for Rx or Tx can only be set to:
      100.0, 103.5, 107.2, 110.9, 114.8, 118.8, 123.0, 127.3, 131.8, 136.5, 141.3, 146.2, 151.4, 156.7, 162.2, 167.9, no tone.
    • the (military VHF low band) 150 Hz tone is only available on the 30 - 88 MHz radio.




    OZ-69 Vehicle Adapter

    Holds one of the transceivers and supplies it with DC power, AF & RF amplification.  Note there's no RF connector on the front panel so the radio's antenna connection is made using the internal mating multi-pin connector. Includes a charger for the battery in the radio.  The On - Off - Covert switch probably implements a receive only mode of operation.

     This is similar to the OF-185.

    These come in different frequency bands:
    Model
    Band  MHz
    OZ-69(V)5/U
    30 - 88
    OZ-69(V)6/U 136 - 174
    OZ-69(V)7/U 403 - 470

    Wanted:  Manuals or other info on this unit.  Contact Brooke


    Racal OZ-69
                  Vehicle Adapter

    Racal OZ-69
                  Vehicle AdapterJ1 RS-232 DB-9f
    J2: Power -16 size, 16m pin
    J3 Ant type-Nm
    J4 Ext Spkr 6m pin
    Gnd lug

    Racal OZ-69
                  Vehicle Adapter

    Racal OZ-69
                  Vehicle Adapter








    RF Amp under large removable panel

    Racal OZ-69
                  Vehicle Adapter

    Racal OZ-69
                  Vehicle Adapter
    A1:
    A2: Micro Controller
    A3: Audio Amp
    A4:
    A7: RF Amp
    J2 Power J4 Spkr
    A: Gray 2 & 3
    B: Green  &  Chassis Gnd 1, 4, 5, 6: nc
    C: Blue
    D: White  &  Chassis Gnd
    E: Brown
    F: Red
    G - R: nc



    Racal OZ-69
                  Vehicle Adapter


    PRC-152 Battery

    I'm putting this battery here because it has the look and feel of the battery used on the PRC-139 & PRC-6725.
    This battery came from Mike Murphy.
    Bottom marked:
    Harris
    CAGE 14034 12041-2100-02
    01/10 003614 52Wh  M EO
    PRC-152 Battery
    PRC-152 Battery
    Looks like all the cells are connected in series and in
    addition there's  a protection circuit for each cell.

    Marked:
    14304-12041-2100-02
    PRC-152 Battery

    Ultralife Batteries
    600167-8
    Circular center & Ring contacts plus the dog ear contacts.
    Looks like 6 of the common Laptop 18650 Li-Ion batteries.


    PRC-148  MBITR Thales Non-Rechargeable DL123 Battery Holder

    Looks like it holds 6 stacks of 2 each DL123 batteries for a total of 12 batteries.  At 3 V per cell that's 36 V for the pack.
    23398 Assy: 4101240-501
    Use DL 123 Lithium Battery 3V

    This battery holder came from Mike Murphy.
    Thales DL123
                  Battery Holder







    Links

    Thales- Thales Communications (formerly Racal)- PRC-139 - Specs - PRC-6725E - specs

    This appears to be a Racal radio that can operate at VHF Low (30-88 MHz), VHF Hi (136-174 MHz) and UHF (403-470 MHz) with a module change and was part of the Scope Shield II program.  Jan 2007 the PRC-139 no longer is on the Thales site??
    Aeronautical Expeditionary Airfield Equipment -

    Over $125 Million in Sales for Racal's Advanced Tactical Radios  -
    MIL-STD-188-220A - Tacter-21 - TCP/IP - Solider Command and Control -  AN/PRC-139(c) radio with GPS (Global Positioning System); helmet mounted display (HMD) (32x24 mm, VGA, 640x480, 8 shades of grey), camera (w/8mm recorder), microphone and earphone; and a ruggedized menu control glove.

    PRC-521 (RT-5113) - Canadian version - Photos - Accesories - Modified Installations
    Back to Brooke's Products for Sale, Military AudioSquad RadioMilitary Information, Personal Home, PRC68.com page

    Page created 1 June 2001.