Radio Glen Transmitter
Posted on Feb 22, 2013 6689
Under: RF Transmitter Circuits
This document describes the transmitter system supplied to Radio Glen for testing as designed and constructed by Henry. The transmitter is supplied in prototype form and has the physical limitations of an instrument constructed using prototyping techniques. The transmitter has been designed to conform to the Radio Authority and Wireless Telegraphy requirements but the user must realise that this transmitter has not passed formal type approval tests. The operating station licensee and the technical manager bear the responsibilty of ensuring that the transmitter is not used in such a way as to cause interference to other wireless services or as to cause danger due to electrical shock or fire. Due to the increased power output capability of the transmitter it is especially essential that the signal distibution system is maintained in good condition and checked regularly.
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Technical Specification: Modulator Unit Power: 240V mains Audio Input: Stereo standard line level 0dbm 775mVrms on XLR sockets balanced input. Indicators: Mains neon, 5V rail LED, 22V rail LED, crystal oven heater LED Controls: Mains on/off rotary switch Frequency Ref: Ovened crystal driving PLL frequency divider Ouput frequency: Supplied as 1602kHz +/- 2Hz for University Radio Glen. (now modified to 1287kHz) RF output level: Approx 2Vpp with 80% modulated AM signal Output connector: Female BNC Case: Standard 19” rack mount ?U Mod bandwidth: -3dB at 6kHz from carrier, -40dB at 9kHz as required by WT regs. Modulation limiting: Will not exceed 100% modulation with transient +10dBm 1kHz tone burst. 5. Technical Specification: PA Unit Power: 240V mains Input: Variable 0.5 to 2Vpp with 80% modulated AM signal Indicators: Mains neon, 30V rail LED, Unregulated supply LED. Controls: Dual on/off for each section. Dual input attenuators for each section. Ouput: 10W AM into 50 ohms from each section. Input connectors: Female BNC Output connectors: Female BNC Input impedance: Approx 1kohm each section Ouput Impedance: 50ohm Output harmonics: 40dB down on the main carrier as required by WT regs This sheet shows the frequency synthesiser and modulator. The 74HC4060 uses a cheap 4.608MHz crystal to develop the 9kHz reference required for the VCO. The internationally agreed channel spacing in Europe...