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One of my Favorite radios

RCA MI-8751 P/O SCR-288
The Swedish Set

N3FRQ Collection
RCA MI-8751 Transmitter Receiver - Part of SCR-288

Transmit Frequency Range;  3500-6300 KHz
Receive Frequency Range:    2300-6500 KHz
Power Output:  4 Watts, AM or CW

In the lead up to WWII, it became clear to the U.S. Army Signal Corps that the existing low-power portable HF transmitter-receivers, based on 1920's technology, would not be adequate for modern requirements.  They commissioned a new set, the SCR-284, but it's development was lagging badly.  It came to their attention, that RCA had a radio in production for the Swedish military that could serve as a stop gap.

The RCA set was designated SCR-288, and orders were place.  The early SCR-288's were delivered with the MI-9751 Radio Receiver & Transmitter.  (MI indicates an RCA Master Item number, an internal standard.)  Later deliveries included the cleaned up and ruggedized BC-474 receiver-transmitter.  The MI-8751 became known as the Swedish set.


Change kept altering the procurement outlook as much as delay. Orders for 3,855 of the SCR-131's, 161's, and 171's which had been "critical" in June simply because nothing else was ready were canceled late in the year in favor of SCR-288's. This was the set which the Swedish Government had ordered; the manufacturer was tooled up for it; and until production could begin on the new American sets which were due to replace the old series, it made an acceptable stopgap. Accordingly,
the supply program classified it under "limited procurement" and the 131, 161, and 171 under "limited standard."


(FY 1941) (1 July 1949 - 30 June 1941)


U.S. Army in World War II, The technical Services, The Signal Corps:  The Emergency. p248

The "Green Books"

The Rmergency:

The Test:

The Outcome:

Earliest pictures of SCR-288 - Ft. Monmouth July 1940.

Pictures from document on: SKYWAVES HOME PAGE

Note that there is only one phone jack on the receiver, and only one cable coming out of the transmitter.  The front panel says AVR-xxx Receiver, and the receiver apparently has two crystal control positions.  The whole set is strikingly similar the the AVR-21 aviation radio shown below.

RCA AVR-21 aviation radio

"Production" MI-8751

  • The front panel is two pieces and has RCA "meatball" markings.
  • The receiver crystal control has been eliminated.
  • Panels have been patched to add a second phone jack, and extra cables.
  • Paint is distinctly grey in sunlight.
  • SCR-288 marking hidden inside case.

BC-474 p/o SCR-288

K4CHE photo

  • The front panel is now all one piece.
  • The case is heavier, and is painted olive drab.
  • Of course, the RCA "meatballs" are not present.


An effective superheterodyne receiver with RF stage and BFO using only 4 tubes.
The triple-function 3A8GT (VT-149) and 1D8GT (VT-148) were introduced by RCA in 1939.

MOPA (Master-Oscillator-Power-Amplifier) transmatter is plate modulated for AM.

Excellent TM-11-250 copy here:



Similar microphones were supplied with RCA home disk recorders in the 1930's, and they show up in the abtique radio community, but the years have not been kind to them.
This is a carbon microphone, but a small mic like the common T-17 does not have enough output to achieve full modulation.

A larger mic, as found in telephones will do the job.  My crude but effective solution is show here.


I've been using this supply, based on a 12-volt receiver dynomotor, for years.  A solid state regulator and Zener diodes provide the appropriate voltages for the receiver,  The 6V6 tubes in the transmitter are replace with 12A6's or 12V6's to keep things simple.


                                                                                          Training at Ft. Devons

Weighs 39 pounds, a lot lighter than SCR-284.
An easy two-man carry

Generator 22 pounds - Accessories Case 8 pounds