Spez. 445 b Bs

Spez. 445 b BS (General military receiver for Army)
Spez. 445 b Bs was manufactured by both Telefunken and Lorenz. It is a four-tube AM tuned RF receiver employing a regenerative detection circuit. The set, accessories and batteries are all contained in one apparatus case. This set was considered obsolete by the time WWII started due to the early electrical and mechanical design, and was superseded by the Torn.E.b. Translated from "Die deutschen Funknachrichtenanlagen bis 1945" by Fritz Trenkle To properly describe the evolution of this receiver, we need to go back to 1928/29. Around this time plans were made for a 5 Watt small radio station that could be portable and mounted in vehicles. This became the 5 Watt transmitter specifications 271 Bs, which was a system that was retired in 1932. After this came the originator of the (old) backpack receiver, which was named the Spez. 276 Bs, and had frontal face plate connections for the batteries, or the Spez 356 Bs with a plug connection for batteries. The case for the 356 Bs was an "armored wood" box where the upper half accommodated the batteries. This receiver was designed as a two-circuit receiver with plug-in coils. It was no longer made of plywood boards, but rather metal front panels with metal partitions and Pertinax strips and was one of the first two-circuit receivers in which the circuits were synchronized by a common scale drive The frequency ranges are likely to have been 950-3150 kHz at the transmitter, 100-6700 kHz at the receiver, (but this was not explicitly mentioned in D-937 of May 1932). Also the Lorenz company in 1929 created a two-circuit power source four-tube backpack receiver EKL 129 with plug-in coils with the range of 100 kHz to 10.0 MHz in three subsections. The tube assembly was 1 x RES 041and 3 RE 074. Only a few of these devices were manufactured for testing with troops. The chassis was made of "Duraluminum". In 1931 Telefunken created a four-tube (RE 074), two circuit backpack receiver "Tornisterempfanger Spez. 445 Bs" = Torn.E. / 24b - 306 which covered the total frequency range of 100 - 6667 kHz with three spool cartriges. It was impractical to install a coil revolver mechanism in these radios because the air coils were too big. Regardless of this limitation, the scale had to be adjusted manually. However, the device already had an injection-molded chassis, was produced in large quantities, and was used together with the 5 Watt Transmitter (5W.S. Spec 449 Bs with the short name 5W.S./24 b 104) which had a total frequency range of 950-3050 kHz, divided into four sections. It was (in contrast to previous "tradition") calibrated directly in frequencies and had very clear construction with its aluminum injection-molded chassis, so the whole family of devices arose from it. An essential step forward was at that time the direct calibration of the device. The transmitter was equipped with two triodes RS-241.

Specifications

YEAR INTRODUCED :	1931

MANUFACTURER:	Telefunken, Lorenz

FREQUENCY RANGE:	0.1 - 7.74 MHz over three plug-in coil units

NUMBER OF CRYSTALS:

PRESET FREQUENCIES:	None

ANTENNA:	Long wire on rod

TUNING:	(MO OR CRYSTAL) NA Direct amplification with regenerative feedback control.

SENSITIVITY:	Low

SELECTIVITY:	Poor

POWER SOURCE:	Batteries. for filament, 4-volt alkaline storage battery (4,8NC10) at 0.25 Amps For plate, 90 -volt dry battery (DIN/VDE 1600) at 10 miliamps. For grid - 3 volts (dry battery)

SIMILAR SETS	Torn. E.b

POWER OUTPUT:

TUBES (TYPE and NUMBER):	4 x RE 074 (triodes)

USE:	With the 5 Watt Transmitter (5W.S. /24a 104) and the 100 Watt Transmitter (LS 100/108).

TYPE OF SIGNAL:	CW, tone and voice.

RANGE: (MILES)

TO COMMUNICATE WITH:

TO REPLACE IN PART:

TRANSPORTATION:	Pack, carried by two men