GAREX TWOMOBILE MK II, Operating Manual

Page 1: ...D R A F T D R A F T D R A F T Garex Twomobile 1 Handbook GAREX TWOMOBILE MK II TWO METRE FM AM TRANSCEIVER OPERATING MANUAL ...

Page 2: ...ulation system phase or amplitude is selected by a front panel switch which is independent of the receiver mode switch thus readily allowing cross mode working The equipment is designed to operate from a nominal 12V DC supply conveniently supplied from a vehicle battery For fixed station use a mains driven power supply delivering 12V DC stabilised at 5 amps maximum is required Under standby condit...

Page 3: ...f fitted Dimensions 12 x 5 x 9 deep Weight l2 lbs 5 7kg Optional features Tone burst generator 1700 or 1750Hz Up to 6 transmit channels RECEIVER Sensitivity 1µV p d input for 500mW audio output with signal to noise ratio of 12dB Audio output 1 watt with less than l0 distortion Intermediate frequencies 1st IF 10 7MHz 2nd IF 455kHz with band pass block filter Squelch An electronic squelch circuit is...

Page 4: ...an FET The second local oscillator is crystal controlled at 10 245MHz producing the second IF of 455kHz The second IF is amplified and passed through a bandpass block filter after which there are a further five stages of amplification Amplitude modulated signals pass via the detector and noise limiter to the mode selection switch Frequency modulated signals are taken from the fourth amplifier stag...

Page 5: ...ing stage VT305 is used Transformer T302 in its collector circuit has two secondary windings which are connected respectively to the signal detector MR302 and the AGC detector MR303 The rectified output from MR303 is fed back via emitter follower VT306 as AGC bias to the RF stages VT1 VT2 and the IF amplifiers VT302 VT303 The rectified output from MR302 passes through the noise limiter MR304 the r...

Page 6: ...rs The multiplier driver and power amplifier use quick heat tetrodes Phase Modulation The output from the crystal oscillator is phase modulated by the variable capacitance diodes and multiplied by the following stages Amplitude Modulation The AF section part of which is used in the receiver provides anode and screen modulation of the transmitter power amplifier ...

Page 7: ...hone is amplified by VT50I and VT502 coupled by T501 to the series diodes MR5OI and MR502 which limit the audio and hence the peak deviation After limiting the audio is taken through a lowpass filter integrated by R511 and C508 and via the peak deviation control VR501 to the variable capacitance diodes MR651 and MR653 AF Section amplitude modulation The microphone output is amplified as described ...

Page 8: ...the transmitter valves The red TX lamp is connected in parallel with the energising coils of RLA and RLB and illuminates when the microphone switch is operated Reversed Polarity Protection A selenium rectifier MR702 is connected across the DC supply when the power switch is on and is normally non conducting If the supply polarity is reversed MR702 will conduct and blow one or both of the supply fu...

Page 9: ... supply lead to the negative Reversal of these connections will blow one or both of the 7A fuses It is important to ensure that the correct rating and type of fuse is used as a replacement The supply voltage for alignment and test purposes is 13 2V measured at the input to the equipment Receiver Connect a 3 5 ohm loudspeaker to the terminal block on the outside of the rear panel With the 12V DC su...

Page 10: ...ck heat valves to reach operating temperature then speak at normal voice level across the face of the microphone at a distance of 2 3 inches do not speak directly at the face of the microphone When first using a particular sntenna system the transmitter should be correctly loaded to the antenna as follows using field strength meter or reflectometer VSWR meter adjust the antenna trimmer accessible ...

Page 11: ...ck the antenna and connections Receiver Locate the positive and negative supply inputs to each Rx board and check that the appropriate voltage is present Typical voltages at various points are shown on the circuit diagrams For the detailed alignment procedure refer to the receiver alignment chart Transmitter Typical voltages at various points are shown on the circuit diagram Voltages are ve refere...

Page 12: ...D R A F T D R A F T D R A F T Garex Twomobile 12 Handbook ...

Page 13: ...D R A F T D R A F T D R A F T Garex Twomobile 13 Handbook ...

Page 14: ...D R A F T D R A F T D R A F T Garex Twomobile 14 Handbook SCHEMATICS ...

Page 15: ...D R A F T D R A F T D R A F T Garex Twomobile 15 Handbook ...

Page 16: ...D R A F T D R A F T D R A F T Garex Twomobile 16 Handbook ...

Page 17: ...D R A F T D R A F T D R A F T Garex Twomobile 17 Handbook ...

Page 18: ...o drop almost to zero Then C902 then charges at a rate controlled by C908 until the logic level is reached when the switching gates change and then block the passage of the tone The delay while C902 charges gives the length of the toneburst With switch S5 in the TONE ON position a toneburst will be transmitted automatically each time the PTT contact is operated Adjustment Using a suitable frequenc...