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Summary of Contents for Larcan TTS250M
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Page 2: General Description
200V and 240V. AMPLIFIER The amplifier design is similar to that employed in LARCAN’s high power model ‘M’ series transmitters. The RF amplifier is located in a self-contained slide out drawer. The power output stage use a pair of dual FET RF power transistors operating Class ‘AB’. - Page 3 Pre-corrector The Pre-correction board comprises three separate sections: an input attenuator, a phase corrector and an output amplifier. The input attenuator is made up of R1 through R3. The adjustable phase corrector comprises L1, CR1, and R4. U1 is an amplifier IC and receives power from voltage regulator U2.
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Page 4: Power Amplifier Module
across R11. The zener diode VR3 will conduct at approximately 22V and forward bias the transistor. Set up Procedure • Set up a power supply to 30V; current limited to 3.5A. • Connect the power supply to E1 of the IPA. The current drawn should be approximately 1.75A. - Page 5 is a starting value. It will be re-adjusted during test for minimum intermods and FM noise. • Connect a 30dB, 20W attenuator to the output of the amplifier. • Apply B+ to both supply connections of the amplifier module. • Apply a low level sweep to the module and measure the gain (be sure to take into account the 30dB pad).
- Page 6 OVER-VOLTAGE PROTECTION BOARD CIRCUIT DESCRIPTION The Over-voltage Protection board consists of an op-amp comparator U2 which compares the incoming raw supply voltage to a reference voltage set up by CR1. The input to the comparator is adjustable via R2. If the input voltage rises above the reference level, the output of the comparator drops to a low value, which lights CR2, an on-board LED.
- Page 7 VSWR and AGC circuits and additionally from U2A which is a ‘mute’ type signal. R5 controls the threshold of control of these signals. The circuit configuration comprising CR1, CR2 and CR3 form a matched attenuator, biased by the output of U2B, R2, R3, R7 and R8.
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Page 8: Power Supply And Control
• Turn the visual carrier switch on the exciter to the ON position. Slowly bring the transmitter up to operating power. • Turn R33 on the Pin Attenuator board for maximum power out then trim it back so the power just starts to drop (about 10%). Reset the output power. •... - Page 9 status is field selectable; either a normally open or a normally closed set of contacts. Amplifier telemetry connections are listed in the table on the following page. FUNCTION CONNECTION AUX INTERLOCK 6TB3-2 REMOTE CONTROL 6TB3-3 REMOTE TELEMETRY 65V SUPPLY 6Z2-TB1-6 REMOTE TELEMETRY 30V SUPPLY 6Z2-TB1-5 REMOTE TELEMETRY FWD POWER...