I think you are referring to not being able to net the rocks to the correct frequency in your channel element. This is usually due to not enough or too much capacitance in the oscillator circuit. Good crystal manufacturers will supply the mid range temperature compensation capacitor with their crystal, others do not.
Anyway this capacitor sits in parallel with the piston trimmer capacitor. You will have to experiment with values to get the right one, but the capacitor should have a NP0 or equivalent temperature coefficient. To find the right value set the trimmer approximately mid range and change values of the compensation cap, while the ICOM is as close to 26.5 degrees Centigrade as possible. If you are low in frequency, decrease the capacitance, if too high, increase it. On Tue, Feb 16, 2010 at 11:54 PM, Nate Duehr <[email protected]> wrote: > > On Feb 16, 2010, at 9:57 PM, KE4ZDG wrote: > >> Hey folks, >> >> I'm working on a GE Mastr II high band repeater. Someone gave me some >> crystals that were made up for 146.010 RX. I installed one in an EC ICOM and >> the best I can adjust for is 146.0064, which sounds really scratchy when I >> inject a >3k deviation signal on 146.010. When I tune the monitor down to >> 146.0064, the RX audio cleans right up. >> >> I've backed out the screw until there's no more threads left in the ICOM. Is >> there a capacitor I can change or add to give me a little more tuning range >> to the ICOM? I just need the crystal to go up a hair more (400 Hz on the >> crystal freq). >> >> I know I'm promoting cheapness by not buying another crystal, but the club >> doesn't have much money to spend. >> >> Thanks, >> >> Jared
