SE-202: SEF

Funkstation SE-202 / SEF (Wireless Station SE-202) consisting of Transmitter SF 21, Receiver EF 21; developed by Brown Boveri.

After the end of World War II, the Swiss Army purchased the „Tank hunter Hetzer“ / G13 which had been produced for the German Wehrmacht by Skoda works, as well as large numbers of the legendary „Jeeps“ from U.S. war surplus.
Brown Bovery developed a two channel frequency modulated wireless station, which did fit inside the equipment bays of the tank destroyers; it was based on a vehicle station EF21 intended for use of police and fire brigades.

Technical Data

Principle: Transceiver, Receiver: Double conversion, IF
Modes: FM (F3)
Frequency range: 30 - 42 MHz, two crystal controlled channels, channel spacing 100 kHz.
Sensitivity: FM (F3) - 20 dB < 1 μV / Selectivity: 30 kHz
Output power: 30 W (short time up to 50 W)

Power Supply

Accumulator / Batteries: set powered from 12 V DC from vehicle battery; for the Jeep with its 6 V vehicle battery, a separate 12 V wireless station battery and generator was necessary.
Mains: Mains power supply BG31 for fixed operation or for training station operating on 115 / 145 / 220 / 250 V, the mains power supply is mounted instead of the rotary converter power supply BU31 directly on the transmitter chassis, in this case, the receiver is powered over a multipole power cable.

Dimensions

Transmitter SF21: 236 x 425 x 240 mm, 16.55 kg
Receiver EF21: 236 x 425 x 210 mm, 15.1 kg
Control Unit KF32: 310 x 154 x 258 mm, 9.5 kg
Control Unit KF28: 198 x 88 x 128 mm, 2 kg

Zubehör

Microtelephon ZT61 (Jeep) or headphones / throat microphone ZT63 (one for use in Jeep or four for use onboard tank)
Control Unit KF32 for the tank hunter version with integrated onboard intercom, KF28 for the Jeep version.
Rotary converter power supply BU31 or for fixed or training setups mains power supply BG31.
Standard antenna is a two segment Rod antenna .
to tune the set, BBC developed a Test unit MD31 and a dummy load MZ31

Bedienung

The vehicle wireless station SE-202 / SEF has been developed by Brown Boveri and came in two variants: the „Jeep station“ and the „tank hunter station“ to be installed in the Panzerjäger „Hetzer“ / G-13. Later it has seen fixed use for training and in „mountain stations“ of the Air Force.

The set consists of two metal cases with the receiver and the transmitter and a control unit, which was simple for the „Jeep station“ and equipped with an on-board intercom for the „tank hunter station“.

The metal container of the transmitter and receiver are stored in a equipment bay in the tank destroyer and under metal covers at both sides of the rear sets of the jeep.
The control unit has a simple channel selector to switch one of the channels „A“ and „B“, a volume control and the one of the tank destroyer a switch and volume control for the „BV“ (on-board intercom) at the right side of the front panel.

The Control unit of the tank destroyer version KF32 comes with an onboard intercom (switch BV). It's controls (main switch, blue pilot lamp, volume control) are found on the right side of the front pannel. In the control unit KF32 al valve 6AC7 and 7Y4 as well as a vibrator NSB/12 are used.
One microtel ZT61 is connected directly to the control unit and another three microphone / headphone combinations ZT63 are connected over the box D38.

The control unit KF28 of the Jeep version as well as the KF29 of the fixed / training version are much simpler and come without active components.

	BBC designation	Sender	Empfänger	Bediengerät
SE-202/m Jeep	CF 41	SF 21	EF 21	KF 28
SE-202/m Pzj	CF 63	SF 21	EF 21	KF 32 (with on board intercom)
SE-202 Instruktionsstation (fixed)	CF 62	SO 21 (with mains power supply BG31)	EO 21	KF 29

Technical Principle

Transmitter SF21: The valve V2 (7C5) acts as main oscillator in the 7,5 - 10,5 MHz range when a channel crystal is plugged in (Crystal frequency = (operation frequency/4) + 500 kHz), it's first harmonic (15 - 21 MHz) is fed to the grid of the driver stage V3 (7C5. After amplification and selection of the first harmonic, the frequency is doubled again for 30 - 42 MHz. In the transmitter output stage V4 (815), two pentode systems act in a push pull arrangement.

Receiver EF21: The antenna signal is apmlified in V1 (7C7); in the first mixer stage V2 (7A8) it is mixed with the oscillator signal from V3 (7C7): From this oscillator oscillating from 7,17 to 11,17 MHz, the third harmonic is used, to generate the final oscillator signal between 21,5 and 33,5 MHz liegt, so that in the mixer, the first IF of 8,5 MHz is generated. This first IF of 8,5 MHz is amplified in two IF stages (V4 and V5, (7C7 each). The valve V6 (7A8) acts as 5 MHz oscillator and second mixer, to generate the second IF of 3,5 MHz. This second IF is amplified in V7 and V8 (7C7, each) and is fed to the limiter V9 (7AG7) and for demodulation to V10 (7A6), discriminator). The audio frequency signal is amplified in V11 (7C6) and in V13 (7C5) as AF output stage; V12 (7C5) is used for the squelch.
V14 (7Y4) acts as rectifier for the plate voltage, coming from the vibrator NSB/12.

Röhrenbestückung

Transmitter SF21: V1 (6AB7, modulator); V2 (7C5, oscillator 7,5-10,5 MHz, 1st frequency doubler); V3 (7C5, 2nd frequency doubler, driver); V4 (815, transmitter final stage); V5 (7A8, crystal oscillator, mixer); V6 (7H7, amplifier, discriminator); V7 (7A6, discriminator); V8 (VR150, voltage stabilizer)

Receiver EF21: V1 (7C7, RF amplifier); V2 (7A8, 1. mixer); V3 (7C7, oscillator 1. IF); V4 (7C7, 1. IF amplifier 8,5 MHz); V5 (7C7, 2. IF amplifier 8,5 MHz); V6 (7A8, 2. mixer & oscillator 5 MHz); V7 (7C7, 3. IF stage 3,5 MHz); V8 (7C7, 4. IF stage 3,5 MHz); V9 (7AG7, limiter); V10 (7A6, discriminator); V11 (7C6, AF amplifier, squelch); V12 (7C5, Squelch); V13 (7C5, AF output amplifier); V14 (7Y4, plate voltage rectifier); vibrator NSB/12

Development

After the end of World War II, the Swiss Army could acquire 160 tank hunter „Hetzer“ / G13; this has been produced in the Tchec Skoda works when thy still had been unter german occupation. At the end of World War II a certain number of these tanks was for sale, these had been completely mounted but the hyd neber seen service. The Swiss Army could acquire these tank for a price of 60'000.- Fr. each.

As the Tank hunter „Hetzer“, which was in service with the German Wehrmacht, was equipped with german wireless sets in Germany, the Swiss units were delivered with empty radio equipment bays. So Brown Boveri got the job to construct a VHF set, that could be fitted in these vehicles.

According to investigations by K. Utzinger (IgUem), the design of the set was most probably based on the american VHF set FMT30 developed by Galvin GMC or Motorola. The development had already started before the WW II years, that's why Brown Boveri was able to deliver their FSE station to the police force in Zurich already in 1941.

Field use

In the years 1948/49 165 units of the „tank hunter“ CF63 and 58 ex. of the CF41 „jeep“ have been acquired, another 15 units were for training purpose; the last SE-202 have been faded out in 1973.