SCR-299, 399 and 499

The SCR-399; “Mobile communication unit” was developed for long-distance communication during the second world war. The US Army was looking for improvements in the transmission range, flexibility and durability compared to the then used SCR-197 and SCR-597 transmitters. In 1942 the Hallicrafters HT-4 was selected as the transmitter for the SCR-299, 399 and 499 and received the military identification number BC-610. Until this selection, the Hallicrafters HT-4 was a respected transmitter that was originally built for use by radio amateurs.

The first radio station of this series was used on 8 November 1942 during operation TORCH where a company of the 829th Signal Service Battalion built up a first communication network that could send messages from the landing beaches to the bases in Gibraltar. Despite the problems with unloading the radio stations from the landing ships, the radio stations from this series had been employed until the installation of the “Permanent Army Command and Administrative Network Stations.” General Dwight Eisenhower complemented the work of the SCR-299, 399 and 499 radio stations during the successful reorganization of the US Army and the last victory over the Germans in Kasserine pass in Tunisia. The broadcasting range of the radio stations exceeded all expectations. There are connections made over distances of 3700 km. The SCR-299, 399 and 499 radio stations provided a reliable radio connection with England during the “North African Campain” and during D-day in Normandie where the radio stations were also used by the English Airborn divisions. Also during the invasion in Sicily and Italy almost all communication was via these radio stations. War correspondents made frequent use of these radio stations which were offered to them by the second and third army “Group Communication Teams.” It has been a time that these radio stations were their only link with England for passing on the news.

This radio station existed in three variants; the SCR-299, built into a Dodge panelvan K-51; SCR-399, built into a shelter / container on the back of the GMC truck and the SCR-499, the set can be used separate and installed in buildings.

SCR-299
SCR-399
SCR-499

The radio station is designed for long-distance communication between 1 and 18 MHz. and could, as said before, bridge distances up to approximately 3700 km. Broadly speaking, the radio station consisted of the following components;

  • BC-610; transmitter with a capacity of 350 watts
  • BC-312; receiver operating on 12 volts
  • BC-342; receiver operating on 115 volts
  • BC-614; “Speech amplifier” the pre-amp
  • BC-939; Antenna tuner

BC-610

The BC-610 is a Hallicrafters HT-4 transmitter which was originally built as a transmitter for radio amateurs in America. The station has been adapted for use by the US Army. This tube transmitter was built so solidly that it functioned in almost all circumstances. About 25,000 of these transmitters have been produced for the US Army.

BC-610

BC-312 and BC-342

These receivers were only different in the power supply. one works at 12 volts and the other at 115 volts. These receivers were used extensively in various radio sets during and after the Second World War. The receiver could receive from 1.5 to 18 MHz.

BC-312

BC-614

The Speech amplifier is the pre-amp of this radio set which converted the three input signals into a signal that the transmitter can handle. One could use this radio station for transmitting morse local, remote morse via a field telephone line, local telephony and remote telephony via a field telephone connection. All these options were combined with the Speech amplifier.

BC-614

BC-939

The antenna tuner is actually part of the transmitter, this is always shown together and as far as I know not used in other sets except the successor of this set which was used by the Dutch army until the 1980s.

BC-939

This radio station also includes various accessories packed in three boxes and two reels with telephone cable. There is a chest for the transmitter; the Chest CH-88-A; which is filled with tuning units and coils with which the transmitter could reach its frequencies. There was also a large chest; the Chest CH-119-A; containing various tools and rolls with cable. The third box is also the bank and was filled with mainly spare parts and the antennas.

Transmitter coil
Tunerunits and coils in chest CH-88-A
Chest overview

PE-95

The radio station also comes with a 3.5 KW PE-95 unit.

PE-95

BC-614 – Speech amplifier

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Speech amplifier frond view.

The BC-614 Speech amplifier is an audio-frequency amplifier which is designed for use with the BC-610 Radio transmitter or transmitters of a similar type. The basic purpose of the speech amplifier is raise a microphone signal to a suitable level for driving the input of the audio circuits of the transmitter.

The speech amplifie does also provides a sidetone to monitor CW transmissions with a headset.

The speech amplifier has its own plate-circuit and gets its power from the transmitter from the left socket on the front.

Technical Specifications

Frequency response;
– Carbon microphone – +/-3 db from 200 to 2000 hz
– Dynamic microphone – +/- 3 db from 200 to 3500 hz
Amplifier type – a-f (audio-frequency)
Type of input signals – Voice
Inputs;
– Carbon microphone
– Dynamic microphone
– External telephone (field telephone – EE-8)
Output – 500 ohms, single-ended
Power output – Approximately 2 watts
Power supply – 115 volts. 50/60 hz
Weight – 31 pounds or 14 kilo’s

Manual : TM 11-5054

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Inside view from the top
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Inside view from the bottom

BC-610 or Hallicrafters HT-4

Nice picture i borrowed from Google

In the early 1940s, the U.S military sought a high-powered radio transmitter capable of infallible voice communications over 100 miles (160 km), sturdy enough to work in all conditions, flexible enough to be able to cover a wide range of frequencies, self-powered and able to operate in motion or at fixed locations. The Hallicrafters HT-4 transmitter was chosen from units available from various U.S. radio manufacturers. The HT-4 was designed for amateur radio use and had been commercially available for several years at a price of approximately $700, rivaling the cost of a car. It was considered compact and stable for its era and could deliver in excess of 300 watts of power for voice or MCW communications and 400 watts during morse code operation. As was typical in physically large vacuum tube equipment, the manual cautions power output is less at higher frequencies. It was quartz crystal controlled, but could be used over a wide range of frequencies through use of the master-oscillator power amplifier.

Modifications requested by the Signal Corps were performed by Hallicrafters’ engineers working with U.S. Army technicians at Fort Monmouth. They made a new version of the HT-4, which was known as the BC-610 transmitter, a part of the SCR-299 mobile communications unit, and production began in 1942. General Dwight Eisenhower credited the SCR-299 in the reorganization of U.S. forces, which led to their victory against the Nazis at Kasserine Pass. The SCR-299 was also used in the Invasion of Sicily and later, Italy.

A BC-610 transmitter was used by double agent Juan Pujol García during WWII as part of Operation Fortitude. Clear reception by the Germans of messages transmitted by García, code name GARBO, were so crucial to the Allied deception that use of the relatively high-powered transmitter was deemed necessary.

Over 25,000 units were produced by Hallicrafters and other allied companies. In 1944, a short subject film was produced by the Jam Handy Organization and sponsored by the Hallicrafters Company detailing how the HT-4 transmitter was adapted for military service and dramatizing its use by the U.S. military during World War II.

Specifications:

  • Frequency coverage: 2 to 18 MHz
  • Mode: AM, CW
  • RF power Output: <400 watts CW, <300 watts AM, MCW
  • Vacuum tubes: Eimac 250TH final, pair 100TH modulator, various rectifier and low level tubes
  • Operating frequency determined by plug-in tuning units and final coils (up to three at once) in addition to FT-171B crystals
  • Signal Corps Radio sets: SCR-299, SCR-399, SCR-499, or GRC-38, AM requires BC-614 (or Hallicrafters HT-5) speech amplifier
  • Weight: 390 lb (177 kg) (without BC-614)
  • Manual : TM 11-826 and TM 11-4057

The “A” through “I” models are the same basic unit with relatively minor component and cosmetic differences.