Hello FrancoItaly and all
There is one optimal frequency 115.674 MHz and two variants of HC-49U quartz crystals.
1st. 115.5278 MHz main freq.
2nd. Overtone quartz 10.695 MHz or 10.700 MHz both are near geometric mean of main LC resonant tanl circuit.
L1 3 turns, wire diameter 1mm, 1.09mm enamelled, at 10 mm coil form, 10.5 mm lenght of coil with 3mm winding pitch.
Primary inductance 0.086 uH or 86 nH
Series resistance - 2.304 mOhm
Parallel resistance - 38.14 KOhm
Parallel capacitance Cs - 0.338 pico
Self resonant freq Fsr is very high 1.0895 GHz, wit Q-factor 619 and ESR 0.1 Ohm at 115.674 MHz
Together wit C10 ~ 22 pico, -3dB(Δf) bandwidth of parallel tank-circuit L1C10 is 302.5 KHz, Z= 63 Ohm and eq.resistance is Req = 21.93 KOhm.
Very probably LRL range is somewhere plus or minus 5Mhz from main oscillating LC tank-circuit freq. It should be from 110.5Mhz - 120.5 MHz. Phenomenon is very complex and no one living could explain it. It's all matter of experiments.
Regards
