On Sat, 01 Jul 2006 02:23:19 -0500, Ben Jackson wrote:
On 2006-06-30, wrote:
From a stability factor point of view those "inverter" based
oscillators are amoung the worst.
Good to know. I was trying to reduce part count -- the quad XOR provides
the two oscillators plus one mixer.
and I bet there are parameter shifts in the "chip" as it warms up
The other parameter shift I was missing was droop in the 5V rail as
the 78L05 warmed up (rapidly!) and noise injected by a MAX202 charge
pump also on that 5V rail. I thought that regulator was just for an
(unused) LCD header, but I was wrong.
Those added elements don't help. However I've used flavors
(both TTL and CMOS) of the circuit and stability is only ok at best.
One use was a simple freq counter (commercial purchase) and I
could never get it to stay zeroed on WWV, it was always 100hz or
more off every time I'd check it. I tried everything and finally
pulled that out and added a simple transistor circuit. After than the
error was usually less than a few hz.
I suggest a discrete Bipolar or FET where you can control the
operating point of the device better.
If I can't tame this VCXO I will try that. This must be how Manhattan
prototyping branches off into "Ugly"...
It do at that.
Allison