Replace C24 on the oscillator PCBA from 24pf to 18pf.
Replace the following components on the exciter PCBA.
Replace C105 on the Audio Processor PCBA from .033uf to 1mf. (This is for a more linear audio response)
Cut 1/8 turn off of the top of the helical resonator coils Z101 & Z102 on the exciter PCBA.
If the exciter is used alone, i.e. without the receiver, the following will apply.
Pin 1 of P902 on the exciter PCBA is used for PTT. Connecting it to regulated +10vdc, pin 8 causes it to transmit.
The RF output which can be anywhere from 50 mw to 150 mw is taken from the exciter PCBA connector J101. (This is the output jack which is usually connected to the PA)
Make sure that P902 pin 10 is connected to system ground.
Audio is injected into the channel guard input at P902 pin 9.
Tuning must begin at the oscillator level. The output from the oscillator PCBA is located at J2 pin 5. The amount of drive at this point is critical to the operation and successful tuning of the exciter. The signal here is in the 50Mhz range and without enough the exciter will never tune correctly if at all.
The oscillator module (FM Icom) has factory selected components to accommodate the characteristics of the crystal that was installed. Replacing the crystal may work fine and it may not. If you are having difficulties in getting enough output from the oscillator PCBA or the frequency adjustment seem difficult or effects the output level, try another module. Changing capacitors in the module may or may not work.
It may be advisable to tack the crystal into the module, plug it into the oscillator PCBA and measure the output. Try 3 or 4 modules and select the one with the greatest output and ease of tuning.
Following the tuning instructions in the manual, use the following level ranges for a guideline. Use a good quality analog meter, preferably a FET VOM to minimize loading. Some meter deflections during tuning are very subtle and a digital meter will not allow you to see them. If you don't achieve the minimum at each stage, you will run into trouble. It is important to watch the output of the exciter on a spectrum analyzer as improper tuning will cause the exciter to run spurious.