BC-224 AND BC-348 AIRCRAFT RADIO RECEIVERS (Revision 7, January 12, 1997) Background: Installed in almost all USAAF (and many USN, British and Canadian) multi-engined transports and bombers used during the fifteen year period from before WWII through the Korean War, BC-224 and BC-348 radio receivers were easy to operate, reliable, and weighed 1/3 less than their ground-hugging cousins, the BC-312, BC-314, BC-342 and BC-344 receivers. BC-224s and BC-348s were used as a component of long-range liaison radio sets, as follows: Signal Corps Radio Receiver Transmitter SCR-187 BC-224 BC-191 SCR-238 BC-224 BC-307 SCR-260 BC-348 BC-349 SCR-287 BC-348 BC-375 Aircraft Radio Communication Set AN/ARC-8 BC-348 ATC or AN/ART-13 The receivers were also used on the ground in Mobile Radio Communication sets, e.g., the AN/MRC-35. A complete BC-348 with dynamotor, its mounting, and its plugs, later became units of, and comprised, Aircraft Radio Receiving set AN/ARR-11. The basic design of these receivers was such that all cabinets, mountings, power plugs and sockets, dynamotors (within primary voltage ratings), dial mechanisms, handles, dial light covers, knobs and switch levers were directly interchangeable between all -B model and later receivers produced by all manufacturers. The ability of the Signal Corps to supply and maintain these receivers was thus greatly enhanced. The BC-224-A receiver, its BD-94-A dynamotor, and its FT-154 mount are unbelievably different in physical appearance both inside and outside from the BC-224-B, and later models, and yet are remarkably similar electrically. As a matter of fact, the BC-224-A looks more like the BC-312 than anything else. The only non-electronic parts interchangeable between the BC-224-A and later models appear to be the connector plug, the main tuning dial spinner knob, and the knobs for the dial light dimmer, volume control, crystal switch, and CW beat frequency oscillator. All the other receivers from the -B series forward were physically similar. Later models substituted a electrically identical 6K6GT output tube for the earlier 41 but, except for the BC-348s -J, -N, and -Q, little else changed. BC-348s -J, -N, and -Q, are a single-ended tube design and were produced using point-to-point wiring, a standard commercial practice. Note that very large orders were placed simultaneously with Belmont Radio (for the BC-348-R) and with Wells Gardner (for the BC-348-Q) in 1943. While the BC-348-Q is of a more modern design, the performance specifications for both designs were identical. Therefore, it does not necessarily follow (as some have suggested) that the -Q model is a better performer than the -R model, or its predecessors. A Brief History: Designed by RCA in the mid-1930s to U.S. Army Signal Corps specifications for a 14-volt DC powered aircraft receiver, the first production BC-224 by RCA was the BC-224-A. Based on Air Corps experience with the BC-224-A, RCA redesigned the receiver to include four separate removable bandswitching coil modules, a redesigned dial and mask assembly, and an improved dynamotor assembly. The newly redesigned receiver became the BC-224-B. Satisfied with the BC-224-B, the Signal Corps had RCA make a 28-volt DC version and called it the BC- 348-B. There was no BC-348-A. The BC-224-A, -B, -C, and -D; and the BC-348-B, and -C, tuned 1.5- 18 mc in six bands. The Signal Corps had the receiver design modified to add a 200-500 kc band and compress the 1.5-18 mc coverage into the remaining five bands. This modified design became the BC-224-E and the BC-348-E. The 200-500 kc and 1.5-18 mc tuning range remained constant for subsequent production of all models. In 1943, the Signal Corps had Belmont Radio remanufacture some of the BC-348-Cs to include the 200-500 kc band. This remanufactured receiver became the BC-348-S. While the BC-224-A used a BD-94-A (14-V) dynamotor and an FT-154 mounting, all the BC-224-B/BC-348-B and later receivers used DM-24 (14-V) and DM-28 (28-V) dynamotors, FT-154 (lettered series) and FT-167 mountings, PL-P103, PL- Q103, and PL-Q103-A plugs. About 90,000 of these receivers were produced: 80 percent of them by Belmont Radio and Wells Gardner in Chicago; the balance by RCA and Stromberg-Carlson, in the New York area. Except for the General Electric dynamotor in the BC-224-A, Eicor, Inc., Russell Electric Co., and Webster-Chicago Corp., all of Chicago, appear to have manufactured all the dynamotors used with these receivers. In 1943, the approximate cost of a complete BC-348-Q was $368--almost 15 times the $25 monthly base pay of an Army private. It has been suggested that BC-348 receivers were copied and manufactured by the U.S.S.R. during War II by the Russian Vefon Works. If anyone has a BC-348 with a Russian nameplate, or with any other indication that it was not manufactured in the U.S., please sound off. Confirmation of this circumstance would indeed be a unique revelation. In the Discovery Channel's "Wings of the Luftwaffe" TV series, during the story of the Ju-52 (the Germans called their Gooney Bird "Iron Annie" or Tante Ju--"Auntie Junkers"), you'll see a completely restored Ju-52 (the one with the yellow engine cowls) sporting a BC-348 (or a BC-224) on the forward right hand side of the passenger/cargo compartment bulkhead--a symbolic act of deference by one fine old lady to another. History by Model Number: The following chart provides a concise picture of the lineage of these receivers. The serial numbers shown are the high numbers reported by members of Boatanchors (or, in the case of the BC-224-A, the quantity covered by its contract). The receivers were not necessarily produced in alphabetical order--look at the contract dates. Unless otherwise specified, missing data does not mean the receiver didn't exist, only that specific information about it has not yet turned up. Please contact me if you are able to provide any corrections, additions, serial numbers, order numbers, or any other information relevant to this file. Thanks, Ken Corwin (kenc@smartdocs.com). MODEL MFR ORDER S/N TLU R NOTES ======== === ================== ===== === = ========================== BC-224-A CRV SC-132373 591 AAA A 1st prod -224 (650 '36/37) BC-224-B CRV 65-NY-40 (8-8-39) 692 BBB A Redesign of -A (1938) BC-224-C CRV 1780-NY-41 228 BBB A BC-224-D CRV 94-PHILA-42 289 BBB A BC-224-E CRV BBB B 200-500 kc band added BC-224-F CDL 634-WFSCPD-42 577 CCC B Output tube changed to 6K6 BC-224-G CRV BBB B Same as -E BC-224-H CRV Not on nameplate 344 BBB B Same as -E BC-224-K CDL CCC B Same as -F BC-224-L CRV BBB B Same as -E ---------------------------------------------------------------------- BC-348-A Does not exist. BC-348-B CRV BBB A 28V version of BC-224-B BC-348-C CRV 1780-NY-41 1529 BBB A BC-348-D Does not exist. Reference 12. BC-348-E CCT BBB B 200-500 kc band added BC-348-F Does not exist. Reference 12. BC-348-G Reference 12. BC-348-H CDL 2356-CHI-41 2717 CCC B Output tube changed to 6K6 BC-348-I Does not exist. Reference 12. BC-348-J CWQ 832-CHI-42 3948 DDD B Sgl-end dsgn; pt-pt wirng BC-348-K CDL 78-WFSCPD-42 787 CCC B Same as -H BC-348-L CDL 146-WFSCPD-42 1571 CCC B Same as -H BC-348-M CCT 147-WF-42 3738 BBB B Same as -E BC-348-N CWQ 144-WF-42 (Note 1) 8913 DDD B Same as -J BC-348-O CRV 145-WF-42 (Note 1) 4880 BBB B Sim. to -E, +adj osc ser pad BC-348-P CCT 2542-WF-42 5487 BBB B Same as -E, +caps 66-1 & -2 BC-348-Q CWQ 2541-WF-42 3329 DDD B Same as -J, +R 87-6, -R 104 BC-348-Q CWQ 11415-WF-43 18111 DDD B Same as -J, +R 87-6, -R 104 BC-348-Q CWQ 928-DAY-DE A122 DDD B Same as -J, +R 87-6, -R 104 BC-348-R CDL 2540-WF-42 11996 CCC B Same as -H, +ceram HFO soc BC-348-R CDL 11414-WF-43 18699 CCC B Same as -H, +ceram HFO soc BC-348-S CDL 8980-WF-43 315 BBB B Same as -O, Remfd -C BC-348-AL ? CCC B Same as -R, AFM 100-5, p 81 ---------------------------------------------------------------------- Note 1. This information appears on a piece of paper glued to the inside of the cabinet, not on the nameplate. ====================================================================== Manufacturer (MFR) codes: CCT = Stromberg-Carlson Telephone Mfg. Co., Inc., Rochester, NY CDL = Belmont Radio Corp., Chicago, IL CRV = RCA Mfg. Co., Inc., Camden, NJ CWQ = Wells Gardner & Co., Chicago, IL Tube Lineup (TLU) codes: AAA = 6B7, 6D6(4), 6F7, 41, 76 BBB = 6B8, 6C5, 6F7, 6J7, 6K7(3), 991, 41 CCC = 6B8, 6C5, 6F7, 6J7, 6K7(3), 991, 6K6GT DDD = 6K6GT, 6SA7, 6SJ7, 6SK7(4), 6SR7 Tuning Range (R) codes (megacycles): Band 1 Band 2 Band 3 Band 4 Band 5 Band 6 A = 1.5-3.0 3.0-5.0 5.0-7.5 7.5-10.5 10.5-14.0 14.0-18.0 B = 0.2-0.5 1.5-3.5 3.5-6.0 6.0- 9.5 9.5-13.5 13.5-18.0 Tube functions: AAA = 1RF(6D6), 2RF(6D6), 1DET(6D6), HFO(76), 1IF(6D6), 2IF/CWO(6F7), 3IF/2DET/AVC(6B7), OUTPUT(41) BBB = 1RF(6K7), 2RF(6K7), 1DET(6J7), HFO(6C5), VR(991), 1IF(6K7), 2IF/CWO(6F7), 3IF/2DET/AVC(6B8), OUTPUT(41) CCC = 1RF(6K7), 2RF(6K7), 1DET(6J7), HFO(6C5), VR(991), 1IF(6K7), 2IF/CWO(6F7), 3IF/2DET/AVC(6B8), OUTPUT(6K6GT) DDD = 1RF(6SK7), 2RF(6SK7), 1DET/HFO(6SA7), 1IF(6SK7), 2IF(6SK7), 3IF(6SJ7), 2DET/AVC/CWO(6SR7), OUTPUT(6K6GT) Commercial equivalent to VT number: 6B7 = VT-68 6F7 = VT- 70 6SA7 = VT-150 41 = VT-48 6B8 = VT-93 6J7 = VT- 91 6SJ7 = VT-116 76 = VT-76 6C5 = VT-65 6K6GT = VT-152 6SK7 = VT-117 NE-48 (ANSI B9A) 6D6 = VT-69 6K7 = VT- 86 6SR7 = VT-233 = RCA-991 ====================================================================== Following is a list of FT-154 Mountings and the receivers for which they are listed as components. With the exception of the FT-154 (without letter suffix), they are interchangeable. Mounting Listed as a component in the manual for Receivers: ========= ========================================================== FT-154 BC-224-A FT-154-C BC-224-C, BC-348-C FT-154-E BC-224-E, BC-224-G, BC-224-H, BC-224-L, BC-348-E, BC-348-M BC-348-O, BC-348-P, BC-348-S FT-154-H BC-224-F, BC-224-K, BC-348-H, BC-348-K, BC-348-L, BC-348-R FT-154-J BC-348-J, BC-348-N, BC-348-Q FT-154-K BC-224-F, BC-224-K, BC-348-H, BC-348-K, BC-348-L, BC-348-R FT-154-L BC-224-E, BC-224-F, BC-224-G, BC-224-H, BC-224-K, BC-224-L BC-348-E, BC-348-H, BC-348-K, BC-348-L, BC-348-M, BC-348-O BC-348-P, BC-348-R, BC-348-S FT-154-P BC-224-E, BC-224-G, BC-224-H, BC-224-L, BC-348-E, BC-348-M BC-348-O, BC-348-P, BC-348-S FT-154-Q BC-348-J, BC-348-N, BC-348-Q FT-154-T BC-224-E, BC-224-F, BC-224-G, BC-224-H, BC-224-K, BC-224-L BC-348-E, BC-348-H, BC-348-K, BC-348-L, BC-348-M, BC-348-O BC-348-P, BC-348-R, BC-348-S FT-154-W BC-224-E, BC-224-G, BC-224-H, BC-224-L, BC-348-E, BC-348-M BC-348-O, BC-348-P, BC-348-S FT-154-AA BC-348-J, BC-348-N, BC-348-Q ====================================================================== Special Note on Receiver Alignment: In manuals other than NAVAER 16-30ARR11-501 (see Reference 5., below), instructions for the alignment of these receivers dictate that the i.f. amplifiers be aligned at 915 kcs, followed by alignment of the crystal filter and beat frequency oscillator. NAVAER 16-30ARR11-501 states, in SECTION III, ALIGNMENT PROCEDURE, paragraph 3-2: "The intermediate frequency amplifiers and the beat frequency oscillator must be aligned to the crystal filter frequency. In the following procedure, the signal generator's output frequency will be the crystal filter frequency unless otherwise stated. The crystal filter frequency should be not more than 1.3 kc above or below 915 kcs." The procedure then describes a method of i.f. amplifier alignment, followed by beat frequency oscillator alignment, alignment of the crystal filter and adjustment of its bandwidth, all centered on the actual frequency of the crystal. ====================================================================== Description: 1. General Radio Receivers BC-224 and BC-348 are locally controlled, eight- tube, six-band superheterodyne receivers designed for use in U.S. Army aircraft. The BC-224-A, -B, -C, and -D; and BC-348-B, and -C receivers tune 1.5 to 18 mc; all others tune 200 to 500 kc and 1.5 to 18 mc. BC- 224 receivers are designed for operation from a 14-volt DC power source; BC-348 receivers from a 28-volt DC power source. Their normal power consumption is 56 watts; or 60 watts when supplying power to accessory equipment such as an LM or BC-221 frequency meter. All controls are located on the front panel where they may be operated easily by the aircraft radio operator. Antenna, ground and headphone connections are made on the front panel. Power and interphone connections are made through a connector plug at the back of the receiver. Each receiver is capable of am, mcw and c-w reception. Either manual or automatic volume control may be selected by a switch on the front panel; likewise normal or extreme selectivity is provided by means of an i-f crystal filter that may be switched in or out of the circuit as desired. A beat frequency oscillator is employed for c-w reception. The audio output impedance may be preset either high or low, according to requirements. The receivers are not intended for remote control and no provision has been made for this operation. 2. Weight and Dimensions Radio Receiver BC-224-A, complete with all tubes and with Dynamotor BD-94-A mounted, assembled with Mounting FT-154 with plug mounted, is 18" wide, 10-1/16 high, 8" deep (including the handle on the tuning knob), and weighs about 42 pounds. Radio Receiver BC-224-B, and later, and BC-348s, complete with all tubes and with Dynamotor DM-24 or DM-28 mounted, assembled with Mounting FT-154-(lettered suffix) with Plug PL-P103, Plug PL-Q103, or Plug PL- Q103-A mounted, are 18" wide, 9-1/2" high, 10-1/2" deep (including the handle on the tuning knob), and weigh about 40 pounds. 3. Cabinet Radio Receiver BC-224-A is housed in a welded aluminum cabinet 18" long, 9-1/8" high, and 6-1/2" deep, which is provided with louvers in the rear and four large holes in the bottom for dynamotor ventilation. An opening is provided at the bottom rear of the cabinet for the connector plug. The exterior of the cabinet has a black wrinkle finish; the inside is flat black. Four mounting studs are riveted to the bottom of the cabinet. Two snap-slides, mounted at the extreme edges of a flange on the lower front edge of the cabinet, are used to lock the cabinet to Mounting FT-154. Radio Receiver BC-224-B, and later, and BC-348s are housed in a spot welded aluminum cabinet 18" long, 8-5/8" high and 8-15/16" deep. There are no louvers or ventilation holes in the cabinet. The top and back of the cabinet are strengthened by embossed grooves that run nearly the length of the cabinet. An opening is provided at the bottom rear of the cabinet for the connector plug. An aluminum casting is mounted over this opening and acts as a seal between the cabinet and the chassis. The exterior of the cabinet has a black wrinkle finish; the inside is flat black. The bottom of the cabinet is reinforced by a stainless steel plate, to which are attached four mounting studs. A flange on the front of the plate mounts two snap-slides which are used to lock the cabinet to Mounting FT-154-(lettered suffix). 4. Chassis The chassis of Radio Receivers BC-224-A is formed from a heavy aluminum plate. The chassis of Radio Receiver BC-224-B, and later, and BC-348s, is a machined aluminum casting with an aluminum plate mounted on each end. These plates have cutouts to facilitate servicing and serve as mountings for parts and as runners for the chassis when it is installed or removed. 5. Dial and Mask The tuning dial of Radio Receiver BC-224-A is calibrated in six frequency ranges and driven at its outer edge by a split gear. This anti-backlash gear is driven by a pinion on the countershaft of the tuning condenser. Dial travel is limited by stops mounted on the tuning condenser. A dial mask with windows is driven by a system of cables and pulleys attached to the band switch shaft and detent wheel mechanism. The dial and mask assembly of Radio Receiver BC-224-B, and later, and BC-348s, is a casting which mounts a dial scale calibrated in six frequency ranges, a dial mask with windows, a band switch shaft, a detent wheel and mechanism, and drive gears. A stop arm provides a positive stop at each end of the frequency range. The use of split gear tuning minimizes backlash. The drive ratio is such that approximately 100 revolutions of the tuning control knob are required to turn the ganged tuning capacitors through the frequency range. The assembly is mounted on the front panel, and indicates the range and frequency to which the receiver is tuned. 6. Dynamotor The Dynamotor Unit BD-94-A of Radio Receiver BC-224-A is located at the lower right corner of the chassis. The Dynamotor Unit consists of a dynamotor machine and low voltage rf filter components enclosed in a ventilated aluminum enclosure. The high voltage filters are enclosed in a separate aluminum enclosure, called the Reactor Pack, which is attached to the dynamotor enclosure. In addition to the power supplied by the Dynamotor Unit to the receiver, there is available at the connector plug 15 milliamperes at about 200 volts for the operation, if necessary, of accessory equipment. The dynamotor assembly of Radio Receiver BC-224-B, and later, and BC-348s, is mounted at the upper left rear corner of the chassis. It consists of Dynamotor DM-24 or Dynamotor DM-28 and an r-f filter unit that supplies all the high voltage direct current for the operation of Radio Receiver BC-224 (DM-24) or Radio Receiver BC-348 (DM-28). In addition to the power supplied by the dynamotor to the receiver, there is available at the connector plug 20 milliamperes at approximately 200 volts for the operation, when necessary, of accessory equipment. To remove the unit for servicing or replacement, disconnect the spade lugs at the 5-screw terminal board and loosen the mounting bolt at each corner of the mounting plate. There is a hole in the dynamotor mounting flange, above the 5-screw terminal board, which is designed to pass a dowel pin mounted on the receiver chassis of all BC-348s if a dynamotor of correct primary voltage is being installed in the receiver. The nominal ratings of these dynamotors are as follows: Input Output --------------- ------------------ Regulation Dynamotor Amperes Volts Milliamperes Volts Percent --------- ------- ----- ------------ ----- ---------- BD-94-A 1.75 13.8 50 225 15 DM-24-(*) 2.45 13.8 70 220 12 DM-28-(*) 1.23 27.9 70 220 12 (*) Any letter. 7. I-F Transformers, Crystal Filter, C-W Oscillator The i-f transformers, crystal filter, and c-w oscillator assemblies of BC-224-A receivers are mounted horizontally in a row along the upper right hand edge of the chassis and above the row of i-f tubes, which are also mounted horizontally; these items on all BC-224-B, and later, and BC-348 models except the BC-348-J, -N, and -Q, are mounted vertically on the left front section of the chassis near the i-f tubes which are also mounted vertically. The crystal filter of the BC-348-J, -N, and -Q, is mounted on the crystal filter switch; its neutralizing coil and the c-w oscillator are mounted on the under side of the chassis. Because fixed capacitors are used across their primaries and secondaries, the i-f transformers are tuned by adjusting their cores. With the crystal filter switch on the panel in the ON position, sharp selectivity is obtained on all bands. The c-w oscillator can be turned on with a switch on the panel and its frequency adjusted by a tuning knob, also on the panel. 8. R-F and Oscillator Units The r-f amplifier and 1st detector tubes of the BC-224-A are mounted horizontally on the top left hand edge of the chassis. The antenna, r-f, detector, and band switch units are not individual sub- assemblies but are assembled together above and below the tuning capacitor which is located on the lower left just behind the front panel. The individual sections are separated by covers and vertical separators. The HFO tube is mounted vertically in an enclosure at the rear of the chassis above a temperature controlled compartment containing the oscillator coils. In Radio Receiver BC-224-B, and later, and BC-348s, the antenna, r- f, 1st detector and oscillator units are sub-assemblies consisting of a shield can, coils, trimmer capacitors, band switch section, resistors, fixed capacitors and, in the oscillator unit, a 6C5 oscillator tube, VT- 65. BC-348-J, -N, and -Q receivers combine the oscillator and 1st detector function in a 6SA7, VT-150, which is located in the oscillator unit in those receivers. The four units are mounted at the right rear of the chassis and are bonded together by common ground straps. All tubes are mounted vertically. The band switch sections are ganged by the band switch drive shaft. On BC-348-J, -N, and -Q receivers, band switch sections are ganged by the use of slotted bars and tension springs. 9. Audio Output Audio output of up to 830 milliwatts is provided by either a 41 or a 6K6GT, which are electrically identical. A match to either a high or low load impedance may be made by soldering the audio output line to the appropriate terminal on Resistor Rack #2 (BC-224-A), or on the output transformer (all other receivers). The high and low matching impedances available on Radio Receiver BC-224-A are approximately 3500 and 500 ohms, respectively. For all other receivers, these matching impedances are approximately 4000 and 300 ohms. 10. Front Panel The front panel of Radio Receiver BC-224-A is attached to the chassis with five bright nickel-plated machine screws. Two handles are mounted on the panel. The front panel and chassis assembly is attached to the cabinet with five captive thumbscrews. The panel has a black wrinkle finish. Controls and switches are each identified by metal nameplates attached with screws to the panel. The front panel of Radio Receiver BC-224-B, and later, and BC-348s, is attached to the chassis and to the end plates by machine screws. Two handles are mounted on the panel. Thumbscrew rods pass through the lower part of these handles and fasten the chassis to the cabinet. On the right side of the panel is a small metal plate held in place by six screws and covering an opening that gives access for servicing to the underside of the r-f tube shelf. Both the front panel and the r-f tube shelf plate have a black wrinkle finish. White lettering identifies each control and indicates the switch positions. The following items are mounted on the front of the panel: antenna and ground binding posts, marked A and G (some panels, instead, are marked ANT. and GND., or just A and G); antenna alignment control, marked ANT. ALIGN (ANTENNA ALIGNMENT on BC-224-A receivers; not on BC- 348-J, -N, or -Q receivers); dial lights rheostat control, marked DIAL LIGHTS; tuning control, marked TUNING; band switch control, marked BAND SWITCH; window frame assembly which covers the dial lights; beat frequency control, marked BEAT FREQ. (BEAT FREQUENCY on BC-224-A); crystal filter control, marked CRYSTAL OUT IN; volume control, marked INCREASE VOL. (INCREASE OUTPUT on BC-224-A); power control, marked AVC OFF MVC; c-w oscillator control, marked C.W. OSC. ON OFF; two telephone jacks, each with a cover assembly, marked TEL (one telephone jack without cover, marked PHONES on BC-224-A); a toggle switch controlling the heaters (not the tube filament) in the HFO compartment, marked HEATER OFF ON (BC-224-A only); and a 2" x 3" nameplate, identifying the receiver's model, order and serial numbers, and its manufacturer. Some of the order numbers (RCA and Wells Gardner), instead of being shown on this nameplate, were printed on a small piece of paper and glued to the rear vertical surface on the inside of the cabinet. The reason for this is unknown. 11. Mounting Mounting FT-154 is comprised of a metal plate upon which four shock absorbers are mounted. A second metal plate, with grooves and cutouts to fit the mounting studs on the bottom of the cabinet and studs to fit the snap-slides, is attached to the top of the shock absorbers. A metal stiffener is attached to the bottom of this plate to strengthen the assembly, and provision is made at the rear of the plate for mounting the connector plug. Mounting FT-154, used with the BC-224-A, is not interchangeable with later Mounting FT-154-(lettered suffix), because of its unique physical characteristics. 12. Connector Plug The eight-contact connector plug which enables power connections at the rear of the receiver is mounted by screws on Mounting FT-154. The wiring terminals are accessible by removing the rear cover on the plug housing. The connector plug, when provided with a straight fitting, is identified as Plug PL-P103. When it is provided with a right angle fitting, it becomes Plug PL-Q103, whether the fitting is mounted toward the right, left, or back of the receiver. If the right angle fitting is supplied with a cable clamp, the connector becomes Plug PL-Q103-A. References: 1. U. S. Army Signal Corps Technical Order No. 08-10-24, 12 June 1936, "Instruction Book for Radio Receiver BC-224-A manufactured by RCA Manufacturing Co., Inc., Camden, N.J., U.S.A., Order No. SC-132373" 2. Army Air Forces Technical Order No. 08-10-119, December 15, 1942; "Instruction Book for Operation and Maintenance of Radio Receiver BC-348-E Radio Receiver BC-348-M Radio Receiver BC-348-P" 3. U.S. Air Force Technical Order 12R2-3BC348-2, revised 15 April 1957; was AN 16-40BC-348-3, 21 June 1948; was AN 08-10-112, 17 July 1943, revised 18 December 1943, revised 30 July 1945; "Handbook Maintenance Instructions Radio Receivers BC-348-J BC-348-N BC-348-Q" 4. U.S. Air Force Technical Order 12R2-3BC-112, revised 15 April 1957; was AN 16-40BC224-2, 20 July 1945, revised 11 May 1948; "Handbook Maintenance Instructions Radio Receivers BC-224-F BC-224-K BC-348-H BC-348-K BC-348-L BC-348-R" 5. NAVAER 16-30ARR11-501, 1 September 1949, "Handbook of Bench Test and Alignment Procedure for Radio Receiver AN/ARR-11" 6. Air Force Manual 100-5, Radio Receivers, 14 December 1956, pages 77 through 81 7. Antique Wireless Association, Inc., "Old Timers Bulletin," Volume 27, Number 2, August, 1986, page 14; The Communication Receiver column; "The BC-348 High Frequency Aircraft Receiver" by Bill Fizette, K3ZJW; "Radio Receiver BC-224/348," by H. A. Robinson, W3LW 8. Department of Defense, Defense Supply Agency, Invitation For Bid, Sale No. 41-5413, Item 223, Bid Opening: 29 April 1975 9. Electric Radio, Number 31, November, 1991, Electric Radio in Uniform, "The BC-348 Receiver," by Walt Hutchens, KJ4KV 10. Electric Radio, Number 85, May, 1996, "The 'Pile,'" by Michael D. Runyan, KK7F 11. U. S. Army Signal Corps "Instruction Book for Radio Receivers BC- 224-C and BC-348-C manufactured by RCA Manufacturing Co., Inc., Camden, N. J., U. S. A. Order No. 1780-NY-41, November 14, 1940, IB-38005-2" 12. "Airborne Radio Equipment Handbook," published by the Signal Section of the Air Service Command, April, 1943 13. AN 08-10-209, 13 November 1943, Revised 1 March 1944, "Handbook of Maintenance Instructions for Radio Receivers BC-348-E, BC-348-M, BC-348-O, BC-348-P, BC-348-S, BC-224-E, BC-224-G, BC-224-H, BC-224- L." (The latest version of this manual is believed to be NAVWEPS or T.O. 16-40BC224-3, revision date unknown.) 14. Electric Radio, Number 90, October, 1996, "My Dream Receiver," by Horst Geipel, WA0NUH Contributors: Tom Bryan; Greg Carter, KX4R; Jay Coward, KE6PPF; Terry Dobler, KJ7F; Robert Downs, WA5CAB; Pedro Duraes, CT1CAH; Steve Finelli, N3NNG; Horst Geipel, WA0NUH; Larry Godek, W0OGH; Stan Griffiths; Ben Hall; Mike Hanz; Dave Hills; Mike Knudsen, W9NRD; Tom Marcotte, N5OFF; Philip McCoy; Kevin McDonald, N5OJF; Dave Metz; Mike Moore, K6SQJ; Ray Mote, K5FTK; Conard Murray, WS4S; Paul Nelson; Pete Petri, WA5JCI; Dave Ragsdale, KF6BOM; Rick Robinson, KF4AR; Bob Roehrig, K9EUI; Mike Runyon, KK7F; Russ Schroeder, W2DYY; Bill Strangfeld, WB8YUW; Brian Summers, VE3JKZ; Paul Thekan, N6FEG; Dave Thompson, K4JRB. Author: Ken Corwin (kenc@smartdocs.com) -- EOF --