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SYNTHESIZER ALIGNMENT
Plug the 6 meters programmed EPROM into the EPROM module Z-273, into the Synthesizer PCB.
Disconnect the Transmitter exciter output J366; And the Receiver Local Oscillator output J365. Set
the supply to 13.8 V.
1: Switch on unit. Adjust the squelch and volume controls so that the loudspeaker is muted
If the Phase Locked Loop (PLL) is unlocked, the channel display will show "95", alert tone will be
sounded, and the dc voltage at TP741 will be 6 V or less than 1.7 V.
If the PLL is locked, either the first channel number will be displayed or else the unit will wait
blank on channel 00 [for RT85] or 01 [for Midland 70-066A] until either the UP or DOWN button
is pressed.
NOTE: If you are using the old RT-80 ten channel head, then above channel numbers displayed
are not applicable.
2: The main Receiver VCO is set to a frequency which is center of the programmed frequencies, By using the
6meters.bin EPROM – set to channel 48 [53.225Mhz].
3: Use the correct alignment tool on all ferrite cores – the ferrite slugs are easily broken.
Connect DC Voltmeter between ground and TP701. On 10 Volt Range.
Adjust L702 such that the de voltage at TP701 is centered on 3.5V for all programmed channels
(i.e. some above 3.5V and some below 3.5V). Voltages will swing between 2 Volts and 4 Volts.
4: Ensuring that the exciter output is disconnected, operate the PTT button. Check the voltage at
TP701 for all channels, and re-adjust L702 for the best balance of voltages around 3.5V for TX
and RX channels. Release the PTT button.
5:
Connect the frequency counter to J365 and adjust CV701 for:
f= (RX freq - 21.4MHz) +- 244Hz : for V HF(HB) and UHF
or
f= (RX freq + 21.4MHz) +- 244Hz : for VHF{LB}
52.525Mhz = Tx frequency then 73.925Mhz = Oscillator frequency.
It is only necessary to check one channel, but this measurement may be made for all
programmed channels.
Note: For special requirements, high side injection may be employed for VHF(HB) and
UHF, and low side injection for VHF(LB); however, a number of components must be
changed for this.
5.
The main transmitter VCO should be adjusted on the highest programmed frequency.
Select channel
Midland 70-066 low Band Conversion to 6 Meters: Part 1
Page 18
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