PRC-47

Brooke Clarke 2000 - 2007

Background

The PRC-47 is an Vietnam ear H.F. radio designed to be carried by two soldiers.  One carries the radio and the other carries the battery.

Function

The AN/PRC-47 shall have the capability for single sideband (SSB) voice, continuous wave (CW), and frequency shift keying (FSK) ground radio communications in the frequency range of 2.000 to 11.999 MHz and shall be operationally compatible with the radio set, AN/TRC-75 [a repackaged & watertight ARC-58, intended for the back of an M38A1 or M170 Jeep.  PP-2352 100A DC to 115 VAC 400 Hz].  The equipment shall provide for direct reading frequency control with a meter indication to aid tuning and antenna loading.  Ten thousand (10,000) channels spaced 1 kHz apart shall be provided.  The equipment shall break down into two packages, each package shall be capable of being quickly attached to a rucksack frame.  one package shall contain the receiver-transmitter and the other shall contain the battery power supply, antenna system and accessories for portable operation.  A watertight transit case shall be provided and be capable of housing all components and accessories.

Major Components

Component Parts of Radio Set AN/PRC-47           NSN 5820-861-3359
RT-671/PRC-47 Receiver Transmetter                                  NSN 5820-082-1599
AS-1320/PRC-47 Antenna 15 foot whip                                NSN 5985-087-2326
AS-1321/PRC-47 Antenna 45 foot long wire                          NSN 5985-087-2305
MX-4430/PRC-47 Battery Terminal Adapter                         NSN 6135-087-2301
U-239/PRC-47 FSK Cable  Adapter                                      NSN 5820-970-6766
BB-451/U Storage Battery                                                    NSN 6140-889-1027
TM 11-6140-208-15
CX-8393/PRC-47 115 VAC 400 Hz Power Cable Assy         NSN 5995-087-2324
CX-8394/PRC-47 28 VDC Power Cable Assembly                   NSN 5995-082(7?)-0487
CX-8395/PRC-47 Battery Power Cable Assembly                   NSN 5995-087-2325
CX-8396/PRC-47 Headphone + Key Branched Cable Assy    NSN 5995-087-2327
CY-3700/PRC-47 Case, Radio Set                                          NSN 5820-062-6748
LS-166U Dynamic Loudspeaker                                            NSN 5965-243-6420
H-33G/PT Handset                                                                NSN 5965-163-9947
H-233/PRC-47 Headset electrical                                            NSN 5965-985-3589
MT-2786/PRC-47 Electricla Equip Legs (2 ea) &   Radials      NSN 5820-062-4758
J-45 Telegraph Key                                                               NSN 5805-171-3370
Rucksack Frame assorted                                                      NSN 5985-984-1774
Battery Retainer                                                                    NSN 5110-115-5049
Canvas Case                                                                          NSN 8105-766-1834
Rucksack                                                                               NSN 5820-987-8793
Rucksack Frames (2 ea)                                                         NSN 8465-558-0151

Optional Components

CV-786/TRC-75 FSK Converter-Oscillator TM 11-5820-527-15
AN/GRA-6 TM 11-5038 Remote Control
CV-2455/PRC-47 Converter-Blower
The power amplifier tube normally operates with no air circulation thus there is a limitation on the transmit time.  When sending RTTY or to allow more talk time a blower can be installed.  There are two plates on the front panel that can be removed to allow cooling the final tube.  You can also remove the tuning chart plate to confirm that the filiments in the final tube are lighting.  The Converter is a modem for RTTY transmission.
 eBay photo1, eBay photo2,

MK-1519 M151 Installation Kit                                               NSN 5820-00-177-1725

UG-1816/PRC-47 Type-N Antenna Adapter

eBay Photo - Fari Radio Photo#1, #2 

Home Brew Adapter

Mount a SO-239 to an insulating plate (about 3 inches in diameter).
Turn a brass  ___x____ screw so that you can solder it into the SO-239 center contact.  This might be a tit or a hole in the screw.
Connect a short length of coax braid to one of the SO-239 ground screws and solder the other end into a phone tip plug.
Connect the ground wire to the nearest push type ground lugs on the PRC-47 front panel.

PP-3518 - may be a power supply

AS-2259 NVIS Antenna System

AN/PRA-4 Test Facilities Kit - cables to allow working on modules out of radio

XLA115 - Homelite 155VAC single phase 400 Hz generator, made from a chain saw engine.  Probably NOT for the PRC-47 since 125 Wattsof gen output is not enough for a 100 Watt output radio.  Might work at low RFputput power setting?

Manuals

TM 11-5820-509-12    (015739.pdf)     OPERATORS AND ORGANIZATIONAL MAINTENANCE MANUAL (INCLUDING REPAI
TM 11-5820-509-35   on line at ETM (NTIS Order Number: TM 11-5820-509-35ING)

photo1 -
photo2 -
 

Maintenence

..WHAT I WAS LOOKING FOR WAS 2N2287 TRANSISTERS AND THE NTE NUMBER 121 CAME UP....WRONG,THE 121 IS RATED AT ONLY 10 AMPS, THE 2N2287 IS RATED AT 20 AMPS. THE RIGHT NUMBER IS NTE 179.

Mike:

The manuals show two different numbers for the choppers....2N2287 and 2N1653.  Something is broken in NTE's x-reference 'cause I looked up 2N2287 in the hardcopy NTE book and came up with NTE 121 which will blow instantly and spectacularly!

Looking up 2N1653 will (I think) show an NTE 180 which will work perfectly in all units so far in spite of being silicon instead of germanium and with no change in biasing.  Mouser carries these for close to $10 each but Frys wants about $6 if you have one near you.

Hope this helps,
Brian, K7AIS

I have already been down this path with those transistors. The ONLY ones I found that would work at all was the ECG 121 MP. Anything else is just a waste of time and money. They blow as soon as power is applyed I found with ALL of the others. The MP stands for matched pair and that will make the differance. By the way ECG was bought out by NTE or Newtone. So now all you will find is the NTE.

One other thing that came to mind. Look up www.alltronics.com and check there stock of transistors. I found that they have a 2N1544 for $2.20 each and that is simular to NTE179.  But think the MP will do the job. I have been using the ones in my unit for about 18 years
and have been doing just fine.

                           73s  Bud

email from AF user

Hello,
I saw your site on the PRC-47. I have been meaning to write you for a while(perhaps I did and have forgotten) on the "other" users of the PRC-47. Your article did mention FAC's. However, I was part of an Air Force FAC Team...called a TACP.(tactical air control party) We used the AN/MRC-107/MRC-107A and later the MRC-108 Radio Control Central...of which the PRC-47 was a part. The MRC series were jeep mounted and the PRC-47 was used as a Back up HF that could be back-packed for close in Air Support. The other radios that you mentioned the PRC-41 were also a part of the MRC-107 (the one I used and are most familar with) Later changes did away with the PRC-41 and used a smaller UHF as this was our primary link to the aircraft. The HF was used for communication with the DASS (Direct Air Support Center) These were Jointly located with Army Units as the this was Air support for ground combat forces. The FAC's and Romad's( I was a romad) (Radio Operator, Maintenance and Driver)were assigned as Liason to the Army Units. A Romad today is a special career field in the Air Force however when I was in we were "drafted" from Radio Maintenance(304X4)as we could repair our own radio's in the field.

Many of the Romads that were sent to Viet Nam were not given credit for their combat roles as they were frequently sent to viet nam on temporary duty (TDY)from units in Korean.(kind of a AF dirty trick)You might add a note to your article concerning this. There were many,many Airmen wounded and killed performing this hazardous task...one that most were hardly trained for. Many had come right from Keesler AFB electronics school...straight to Korean...then to Viet Nam.

As for as the PRC-47 goes I have one that I use on ARMY MARS voice nets today. I power it from a 24 volt power supply built from a old marquette garage battery charger. I used a 35 ampere full-wave bridge rectifier on a fan cooled heatsink,with a capacitor input filter and selected the tap that gives me 28 volts.( I remembered our jeep 24 volts would measure 28 when running and this worked fine. The supply is unregulated but the battery charger transformer is an older one with a massive Iron core and provides adaquate bulk regulation. I fould a article on line to let it move the frequency around and I disabled the VOX which I found annoying. (there is a green jumper inside to do this. Someone suggested this and I seem to recall something about it from MRC-107 school) It is still a fine radio today. I enjoy operating it unless...The only thing it doesn't have is some of the fancy controls for helping with interference...but that is what being a "real" radio operator is all about anyway,right? Getting the copy through adverse conditions.

I did enjoy the read and thanks for putting up the site.
Best Wishes,
D.H.

Links

So Now You Have A PRC-47 - by Dennis Starks
PRC-47 (Collins) LSB/USB Conversion Kit -
KK6IL Home of Mechanical Filters - Shortwave Receiver Modifications - PRC-47 LSB Sideband Conversion -
PRC-47 Variable Tune Modification - First version with error in resistor values
Mission: Provide variable frequency control for the PRC-47 -  Second version of Variable Tune Mod with correct values
The PRC-47 HF SSB/CW/RATT Transceiver by N6CC
PRC-47 Modifications by K6JCA - uses Silicon PNP 2N5884 to replace the Germanium Q1 & Q2 power supply inverter driver transistors.



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