Inhaltsverzeichnis
SE-226
SE-226, Racal Syncal TRA 921B manpack radio; produced by Racal.
Under special conditions, when typical military VHF communication is not feasible, shortwave communications are still to be used, because ionospheric propagation typical can be used. For these special needs, the Swiss Army decided to acquire the shortwave manpack transceiver Racal Syncal TRA 921B, it got the military designation SE-226.
The transceiver can be used as manpack set on a carrying frame, installed on a vehile or in a fixed installation setting with an external inverted V dipole antenna. The SE-226 can be operated remotely by means of the FBA-227/412 remote control unit.
Technical Data
- Frequency range: 2000 - 7999 kHz, decadic frequency selector knobs , 1 kHz tuning steps
Power Supply
- Accumulator / Batteries: 18 V NiCd accumulator (Akkumulator MA 948B, 3,5 Ah) or 12 / 24 V from vehicle battery
Dimensions
- mm, 11 kg
Accessories
- The standard antenna is a portable antenna (2,4 m whip antenna) or an inverted V dipole antenna on a 9 m mast.
- To charge the accumulator MA 948B, the charging unit ALGT-226 (MA 945 X) is used, it can be powered from 12-15 V or 24-30 V DC or 198 - 231 V mains.
- Speaker MA 988 B increases the audio output to 500 mW, it is powered directly from the accumulator from the transceiver, it has no individual power switch.
- The Remote control FBA 227/412 (from the station material SE-227) can also be used to remotely control the SE-226.
- Speech encryption is possible with the SVZ-226.
Operation
To operate the set, a well charged NiCd accumulator has to be mounted on the bottom part of the transceiver; the charging unit ALGT-226 can be powered from 12 or 24 V vehicle battery voltage or 220 V mains.
The microtel, the cable of the handset with headphone, microphone and an integrated push-to-talk button, has to be plugged in the socket in the left lower corner on the frontplate of the transceiver. The whip antenna or the cable of the dipole antenna are connected to the corresponding jack in the right upper corner of the frontpanel.
The modes switch is set to AM VOICE for AM telephony or to VOICE LSB for single sideband operation. The same switch is used as mains switch. Four rotary controls in the upper row of controls are used to select the operation frequency.
In reception mode, the GAIN control is used to adjust the receiver volume. In transmission mode, HIGH or LOW POWER can be selected. When the mode switch is set to TUNE, the control TUNE ist used to tune the set to maximum antenna current. Then the transmission mode VOICE AM or VOICE LSB/USB is selected and a communications check can be performed. If the signal strength is sufficient, the transmittercan be set to reduced output power (LOW POWER), to save energy and enable a longer accumulator operation time.
Technical Principle
The antenna connector is protected by two antiparallel diodes from overloading. The antenna signal is mixed with the signal of the VCO, a PLL synthesizer, to generate an intermediate frequency of 10,7 MHz. The signal then is fed through the IF filters to the AM demodulator. For single sideband demodulation, a 10.7 MHz heterodyne oscillator signal is mixed. The audio signal ist amplified and fed to the headphones jack, an AGC circuit acts on the IF and AF stages to keep the output signal stable.
In the transmitter module, in AM mode, the AF signal is modulated onto a 10.7 MHz subcarrier; for A2 modulated telegraphy, a 1000 Hz tone is added.
In the mixer stage, the 10.7 MHz signal is mixed with the VCO output to generate the definite output RF signal. The subcarrier signal is eliminated and the RF signal is fed to the exciter and RF output stages. In position TUNE of the mode switch, the unmodulated signal is fed to the antenna tuning circuit. A variable inductance is used to tune the set to maximum antenna current, which is displayed on a small instrument. The transmitter can be traced by direction finding systems during this procedure, which is a serious drawback.
The VCO is a PLL synthesizer oscillating between 12,7 - 18,699 kHz, for the 10.7 MHz subcarrier, the 107th harmonic of a 100 kHz oscillator is selected.
Component layout
The transceiver is completely solid state.
Development
The Syncal TRA 921B has been developed by Racal in 1970/72, for the Swiss army, a number of 565 sets has been acquired, they were introduced in 1976/7; the speech scrambling system SVZ-226 was added in 1985.
Field use
The shortwave transceiver had been evaluated for ionospheric communication in the Swiss prealps with their difficult topography. The transmitter output power turned out to be too low for an efficient use.
The SE-226 had mainly be used by parachutists of the alpine units and the sets have been withdrawn in 2004.