[DSP-10] PLL problems

[Gérard Parat / F6FGZ]

Hi,

Things improve.

(1) Xtal is tuned at 10 MHz since I changed C109 from 10 to 39 pF (it was not very
far before but I like perfection:). BTW, I resolder C110 rotor to the screw when
I realized that rotating wasn't working ;-). I measured the frequency at pin2/U7
to avoid loading the oscillator. There is a normal small drift with temperature.

(2) U104 PLL is locking but not at the right frequency (around 96 MHz at C127/LO).
For 112.7 MHz on UHFA display I have 0.31V (lower limit before unlocking) at
R104/R105 junction, and for 115.4 MHz on UHFA display I have 4.76V (upper limit
before unlocking). So it is working well except that I have to find why VCO is too
low in frequency. I don't think I swap TOKO coils because of the great difference
between 0.1 uH and 2.2 uH. It might be around C141, C117 or C118 to check the
values. Maybe FMMV2101 diodes ?

(3) U7 PLL is locking at the right frequency by adjusting the turns spacing on
L21 coil.

Hints welcome for Q101 oscillator ;-)

--
73 Gérard F6FGZ