Hello Tobias and everyone else.
Thanks for the detailed info, much appreciated.
I managed to change the divider again, but this is probably the last
time as a pad is lifting. I also put back a 22k resistor for the 10K
R16. The new divider one didn't have any output at all, save the
tiniest bit of ripple:( So I put back the 10K and output was
intermittent and much like before. But I noticed if i touched the
divider on its plastic shell the the thing gave a much better output,
good square waves, but they would either stop themselves, or if power
to the board was removed then re-applied, it wouldn't start. The input
was on frequency and strong. But now I could sometimes just hover
a finger right above the divider chip and it appeared a capacitive
effect would start it.
When it did output clean square waves they too were on frequency.
There was a proper 90 degree phase shift. I then put in a 6.8k for R16
and it's better still. Dare I go lower, or is this telling me
something I am not hearing?I haven't changed the crystal yet. I don't
think the issue is now the oscillator itself, but driving the divider.
I am sure Andy is right that a Schmitt trigger buffer would be best,
but I didn't really want to start redesigning something I know others
have had running 24 hours a day with superb results.
I'll upload the oscillator wave form at pin 3 of the divider as it is
now.
http://www.gatesgarth.com/newR17-to--pin3.jpg
Friday, January 26, 2018, 9:33:04 PM, you wrote:
> Hi Chris !
> The first screenshot shows an un-symmetrical square-wave that will
> generate two frequencies to the 1:4 divider and Tayloe-mixer. An FFT of
> this signal (R17-to-pin3) should show two peaks and not only one as
> expected. A standard frequency counter will show only the arithmetic
> mean value of both frequencies, as it is just adding zero-crossings
> during gate-time.
> The Softrock series 6.x had a different type of I/Q divider that used
> three flips-flops. They did not have a problem with such an
> un-symmetrical square-wave, as there was an inherent divider by two,
> which forced the oscillator signal to be symmetrical to the mixer.
> You could try to move the bias-level of Q2 transistor to a voltage where
> the output (square-wave) signal of Q2 will be almost symmetrical.
> If the oscillator at Q1 is not running smoothly, this is where to look
> for variations of C's or R's to make it run stable.
> 73 de dg3lv Tobias
--
Best regards,
Chris mailto:[email protected]
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