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====== AN/PRC-47 ======
AN/PRC-47 resp. RT-671, manufactured by [[Collins]], licence production [[Bendix]].

The **AN/PRC-47** radio is a medium-power transceiver with frequency synthesis that was primarily used by Special Forces. The set was first widely used in the Vietnam War.

{{:images:mil-usa-prc-47.jpg?direct&800|Collins AN/PRC-47}}
===== Technical data =====
  * [[Principle]]: [[transceiver]]
  * [[Operation modes]]: [[A1]], [[SSB|SSB (USB)]], [[FSK]]
  * [[Frequency range]]: SW (2 - 12 MHz)
  * [[Frequency display]]: mechanical [[digital display]] 1 kHz
  * [[Frequency memory]]: none
  * [[Signal strength indicator]]: [[S-meter]]
  * [[Transmit power]]: Low 20 watts, High 100 watts

==== Power supply ====
  * [[Mains operation]]: 110 V (400 Hz)
  * [[Batteries]]: 24 V (with adapter / battery box MX-4430 / PRC-47)

==== Dimensions ====
  * 178 x 343 x 540 mm, weight 19 kg

==== Accessories ====
  * CW-647 cover with brief operating instructions
  * Adapter / battery box MX-4430 / PRC-47
  * BB-541 silver / zinc accumulator
  * AS-1320 rod antenna or AS-1321 long wire antenna
  * H-33 handset, LS-166 loudspeaker, H-233 headset, J-45 Morse key
  * CV-2455 RTTY add-on

----

{{:images:mil-usa-prc-47-front.jpg?direct&800|Collins AN/PRC-47}}
===== Operation =====
The AN/PRC-47 transceiver was developed by [[Collins]] in the mid-sixties and was mainly used by Special Forces, for example in the Vietnam War.

The transceiver can be operated with 110 V (400 Hz, corresponding to the common aircraft on-board voltage in the sixties) or with 24 DC.

{{ :images:mil-usa-prc-47-dial.jpg?direct&400|Frequency display}}The frequency processing in the shortwave range 2 - 12 MHz is realised by frequency synthesis and the operating frequency is displayed on a mechanical digital frequency display (similar to an analogue odometer). Below the frequency display is the operating mode switch for the low and high transmission power, which is also used to activate the display illumination. When the BATTERY TEST button to the right of the frequency display is pressed, the battery voltage is displayed.

A rod antenna or a long-wire antenna can be connected to the antenna socket on the left of the front panel. When the switch is in the TUNE position (caution: RF is emitted), the set is ready for the tuning process. Depending on the antenna connected, the approximate setting of the antenna tuning LOAD and TUNE is determined on the nomogram and set. Both controls have a fine adjustment with a 0 - 100 graduation on the inner ring of the control. With each turn, the outer ring with the numbers 0 - 38 moves one step further. Depending on the antenna length and frequency, the approximate position of the outer ring (KNOB TURNS) can be taken from the tuning nomogram.

The XMTR PWR is first moved to the LOw position and tuned to the maximum deflection of the measuring instrument using the XMTR LOAD and TUNE transmitter controls; the needle is moved to the centre position using the small central M ADJ control when it reaches the stop. When the maximum deflection of the measuring instrument is reached with the TUNE and LOAD controls, the LOAD is increased further (clockwise) until the instrument drops 1 - 2 steps and checked to see whether a slightly higher value can be achieved by adjusting TUNE. Then adjust the LOAD anti-clockwise until the instrument drops by 1 - 2 levels and check whether an even better maximum can be achieved with the TUNE control. Finally, the tuning power switch is quickly "peaked" to maximum deflection in the HI position as described above. To complete the tuning process, return the XMTR POWER tuning switch to the OFF position and tighten the LOCK screw to prevent accidental detuning.

Once the tuning process is complete, the set can be made ready for operation with the switch below the antenna base in the OPR position.

===== Technical principle =====
Transceiver

==== Components ====
The set is equipped with tubes in the output stage.

===== Technical documentation =====
  * [[https://www.radionerds.com/images/5/5d/TM_11-5820-509-12.pdf|TM 11-5820-509-12 Operators Manual]]
  * [[https://www.radionerds.com/images/c/c9/TM_11-5820-509-35.pdf|TM 11-5820-509-35 Maintenance Manual]]

==== Development ====
{{gallery>:images?mil-usa-prc-47*.jpg&0&80x80&lightbox&showtitle&titlesort}}
==== Further information ====
  * [[https://www.radionerds.com/index.php/AN~PRC-47|PRC-47 on the website of www.radionerds.com]]