The project is to design and build a low-cost and power-efficient 457 kHz CW beacon transmitter and receiver. Detailed specifications and sources of circuit ideas will be provided. Implementation will involve using discrete analog components such as FETs, crystals, inductors, etc. The project involves mainly analog design and is suitable for those with an interest in this area.
The detailed specifications are in the form of a European standard, EN 282:1991 which is based on the standard DIN 32 924. The important technical specifications are as follows:
transmit frequency: 457 +/- 0.1 kHz
transmit field strength: between 0.5 and 2.16 mA/m at 1 m
receiver sensitivity: 80 nA/m for 6 dB (S+N)/N at speaker/earphone output
modulation: A1A (carrier on/off)
turn-on time: >70 ms
turn-off time: >200 ms
period: 0.9 +/- 0.4 s
operating temperature: -20 to 40 C
storage temperature: -30 to 50 C
operating time: 200 hours transmit at 10C followed by
1 hour receive at -10C