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IC-471 A/H Trimmer Cap Alignment | Radioaficion Ham Radio

IC-471 A/H Trimmer Cap Alignment


Icom IC-471 A/H Trimmer Cap Alignment Procedures after Replacement

1. Replace all plastic trimmer capacitors in PLL/VCO and RF/YGR circuits with ceramic types, 6pf, 10pf, and 20pf, as called for in manual.
2. Monitor J4 with a spectrum analyzer for a signal in the 265 MHz range. Adjust C16, C18, C25, C29, C35, and C38 for peak on analyzer. (Don't use an IFR 1200 service monitor; the signal will overload its analyzer.) Output level at J4 should be 0db or greater. Switch between 430 and 440 MGz on the radio and fine tune the previous listed caps for no more than a 2db variance between the two signals.
3. Monitor PLL output with a spectrum analyzer (not IFR1200) and adjust C58, C61, C70, C76, and C79 for peak signal. This must be a minimum of Odb. Next, fine tune for no more than a 2db variance between 430 and 449 MHz in 1 MHz steps.
4. Align 10.25 MHz oscillator on PLL unit.
5. Align VCO as per the service manual alignment procedure.
6. Set the 430 band frequency and 440 band frequency as per the service manual.
7. Realign RF/YGR unit for maximum performance. Alignment at 440 MHz will usually yield good performance from 430 to 449.995 MHz.

©1997 ICOM America, Inc.

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