10/12/2008

Silicon Two Watt Short Wave Transceiver



The Chinese military Silicon Two Watt radio was developed by Nanjing Wireless manufactory in 1969 to replace the very heavy Type 71 Regiment-Battalion Level HF tube radio. In early 1970, the production of Silicon 2 W had spread to 14 manufactories nation wide. It was finally certified by military in May 1973 as Type 73 Regiment-Battalion Level Short Wave transceiver. Its common name is Silicon Two Watt since it is first field radio to use all silicon transistors from the beginning. Interestingly, the radio name tag uses its common name instead of its former military name. The manufactory name is Comm 251. In mid 70s, the second version is introduced as Type 73B or Silicon 2 Watt II or Comm 251A. The production decreased from 1976 and it was finally replaced by Ten Watt Frequency Synthesised SSB transceiver in early 80s.



Silicon Two Watt is an all silicon transistors backpack short ware transceiver. It has two operation modes, Voice and CW. Unlike Type 81 Compact, the voice mode is its primary operation mode. It covers 1.7 to 6.0 MHz in two bands (1.7-3.2 and 3.2-6.0 MHz). Every 0.2 MHz, there is a crystal controlled alignment point to align the radio frequency. The transmitting power is 2 W in CW mode and 1 W in voice mode. Range is about 10 KM in day time and 5 KM in night time using 1.5 meter antenna in normal battle field condition.



The radio weights 8.5 kg with batteries, 1.5 meter antenna and headset. It measures 230 x 110 x 345 mm. It is powered by two 12 V unit batteries, plus one 1.5V D size battery cell for panel light. The battery box is in the bottom portion of the radio and it has its own access hatch. With 3:1 transmitting/receiving ratio, it could work for 30 hours with two unit batteries. It mainly uses 1.5 meter antenna (with a configurable inductance coil to increate its effective height and a five star radiator). It could also use 15 meter wire antenna and 44-meter dipole antenna, plus a 3-meter wire antenna for receiver to improve the receiving effectiveness.



The receiving and transmitting frequencies are set separately, so that radio could work on the same frequency for transmitting/receiving, or it could work on different frequencies. The transmitting/receiving switching is controlled by a PTT switch built into handhold microphone, or by telegraph key, which in turn controls a relay to control transmitting/receiving circuit. Frequency knob has two rings, outer/bottom one has 1:1 turn ratio, the center/tip one has 40:1 turn ratio for fine tune.



On the control panel, controls and display at the left side are for receiving and that of right side are for transmitting. The radio power switch is on left side of radio battery box so that the operator still has basic control of the radio when it is in the move and the control panel lid is closed.



The transmitting is not straight forward comparing to a modern transceiver. The antenna/transmitting power amplifier has to be tuned before transmitting, or facing the risk of getting the amplifier transistor fried. The tune is achieved by adjusting inductor and capacitor knobs to the first highest transmitting current indicated by the meter at the upper left side of the control panel. Little skill is needed here.



The radio is well built for military field usage. Every control knob is water tight. The radio is fully operational in rain/snow condition. When the control panel lid is closed, the radio can flow cross a river without further water tightening measure. Its operation environment temperature is from -40 to +50 degree Celsius.



My sample was an early version made in 1975 with a serial number of 751600. It has a mark, 9th squadron, on the carrying case. It was very likely belong to a communication unit in Regiment HQ.



Unlike its bigger brother, Type 81 Compact, Silicon Two Watt was a successful story from the beginning. The feedback from troop was very positive. It is approved by that there is only one improved version introduced during its more than ten years service life in PLA. It was widely used in Sino-Vietnam conflict happened in early 1979. It was usually equipped down to company level during that conflict. Interestingly, Vietnam troop also used Silicon Two Watt supplied to them by China in early and mid 70s. Brothers and Comrades up to 1977, Enemy and Foe in 1978, full scale armed conflict in February 1979, what a crazy world!