PA3DBJ
Tuning the Storno CQP4110 (VHF 144 - 176 MHz)
This is quite easy, but you need a valid programmed Personality PROM, plus some simple tools before you can start.
If you open the transceiver, you notice that the RF trimmers are accesible ONLY IF THE MAIN BOARD IS REMOVED ! Now this is a problem, because this way you will lose all electrical connections. So first thing we need to have are a couple of extender cables, that fit the connectors at the sides of the boards. These should be long enough to readjust the trimmers easily, but no longer than abt. 15 cm.
You will need two sets of 9, one set of 6 and one set of 13 cords.
Another thing we need, is an adapter to a 50 Ohms BNC or N-type plug to screw into the aerial socket. They are available from Storno (Motorola), or you can try to find one in a (surplus or telecommunications) shop.
Once we have got our extender cables and adapter, we need to have the equipment we normally use to readjust our radio equipment:
- a regulated power supply (2 A), set to 7.2 Volts,
- an AF signal generator,
- an RF signal generator,
- a test receiver or spectrum analyser,
- a Watt meter,
- a frequency counter,
- a high impedance ( 0.5 MOhm or better) voltmeter,
- a 1 A current meter.
- a 50 Ohms, 2 W dummy load,
- an RF diode probe, plus some tuning tools.
A distorsion meter and a deviation meter can be a great help too.
Transmitter Adjustment
- Check: Connect the RF output to the dummy load and switch on the radio. Power consumption should be less than 30 mA.
- Ref. Freq.: Connect the frequency counter to P3 pin 13: CLOCK. Adjust C533 for a reading of 6.4 or 6.5 MHz +/- 10 Hz.
- VCO: Set the ADC potentiometer R115 to minimum (anticlockwise). Key the transmitter and read the current consumption. This should be less than 1 A.
Connect the voltmeter to P3 pin 7: OUT OF LOCK. Key the transmitter. Adjust C504 for 0 Volt steady reading.
Connect the voltmeter to TP4. Adjust C504 for a reading of 3 Volts. Check that the voltage is 1 - 4 Volts on all channels.
- Tx Power: Connect the Wattmeter to the antenna connector. Key the transmitter. Adjust R115 for rated power output. The current drain should not exceed 1 A at this output level.
- Tx Freq: Connect the Wattmeter to the antenna connector. Connect the frequency counter to the monitor output of the Wattmeter. Adjust C533 for Tx Freq. +/- 0.2 ppm (30 Hz at 150 MHz).
- Tx modulation: A special test box is used for this measurement. As an alternative the peak frequency deviation can be measured during a normal voice transmission. Adjust R812 for +/- 5 kHz (CQP4112), +/- 4 kHz (CQP4113), or +/- 2.5 kHz (CQP4114).
Receiver Adjustment
- VCO: Connect the voltmeter to P3 pin 7: OUT OF LOCK. Preset L508: 2/3 out of the coil at high end of the band, fully down in coil form at low end. Adjust C514 for 0 Volt steady reading.
Connect the voltmeter to TP4. Adjust C514 for a reading of 3 Volts. Check that the voltage is 1 - 4 Volts on all channels.
- Rx Injection signal: Connect the diode probe (connected to the voltmeter) to TP2. Adjust L508 for maximum voltmeter reading (0.2 V +/- 0.1 V).
- IF Signal: Connect the signal generator to the antenna connector and set it to the Rx frequency. Output level: 100 mV, Modulation: 1000 Hz FM, deviation: +/- 3.5 kHz (CQP4112), +/- 2.8 kHz (CQP4113), +/- 1.75 kHz (CQP4114). Connect the diode probe to the voltmeter to TP3. Reduce generator output until voltage drops below 1 Volt.
Adjust L402 and L308 for maximum voltmeter reading.
Set signal generator level to 100 mV. Adjust L403 for maximum audio level / minimum distortion (this is normally done using the special test box).
- AF Line level: Connect the AF voltmeter to J906, pin 14: AF OUT. Set signal generator (100 mV). Adjust R409 for 110 mV +/- 5 mV.
- Front End: Connect the signal generator. Set output to abt. 12 dB SINAD. Connect a distortion meter (normally to the test box). Adjust L306, L305, L303, L302 and L508.
Reduce signal generator output to maintain 12 dB SINAD. Repeat adjustments until no further improvement is possible. Check on all channels : 12 dB SINAD at less than 0.45 microvolts.
- SQUELCH: At 12 dB SINAD, adjust R420 until the squelch just opens. Vary the signal generator output slowly up and down. Check squelch opening level: 12 dB SINAD, squelch closing level: 6-10 dB SINAD.
If the frequency is not within specifications after the radio is closed, the 6.40 (or 6.50) MHz reference frequency needs to be readjusted.
Please mail me if you have any comments.
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