[DSP-10] 126 MHz PLL now locking! Now need a 6.8 pf cap

[Courtney Duncan]

Yes Mike, that was it.  I put in blocking cap in the circiut (except I 
could only find a 47 ohm resistor instead of a 51).  Now all the 
waveforms on U104 are as expected and I'm locked up at 126.000 MHz.  Hot 
Dog!

The input reference waveform on U7-1 is also as expected but it's still 
not locking.

I need a 6.8 pf cap to swap into the C117 spot so I can tune with L102. 
  It's OK for now with the slug removed (as suggested), voltage at the 
top of R104 is 1.205 V, but I'd like to have it be properly tunable.

Dan, I see in the AMSAT kitting list that you had more than 50 of those 
6.8 pf caps left from the process.  Are you in a position where it would 
be convenient to locate and mail me a couple?

I have the C108 and C109 parts left over from not implementing the 
crystal oscillator and if I could put the 22 pf in series with the 
existing 10 pf, that would be perfect.  Unfortunately, I installed them 
before I uninstalled them and one of them is obviously damaged.  Maybe 
both.  In any case, I can't tell them apart and my cap meter doesn't go 
near that low.  It would be best to just use a new correct part anyway.

If you don't still have these handy, I'll just put it on the list for 
some future order with Digikey or whoever.

Courtney, n5bf/6

kd7ts wrote:
> The data sheet does mention that TTL and direct CMOS are common 
> applications to drive the '1501, however.... they also mention that the 
> input pin has it's own internal bias and they recommend A.C. coupling.
> 
> They show 51 ohms shunting the input cable then .01 uF in series to the 
> osc pin in one example.
> 
> It is not uncommon to find oscillators that have DC paths in their 
> output path. Maybe this would be worth checking.
> 
> Mike KD7TS
> 
>