[time-nuts] Broken Ovenaire OSC 85-50

J. L. Trantham jltran at worldnet.att.net
Mon Jul 6 01:12:27 UTC 2009


Bruce, Pascal, and anyone else,

Stanley Reynolds has hosted my pictures of the unit as well as the
schematic.

The link is here:  http://www.n4iqt.com/JLTrantham/85-50/

Hopefully, this will be helpful to someone in the future.

I appreciate all the effort everyone has put into this and it will take me
months to 'digest' all the information.

I put the counter to work today and it functioned well.  I am going to leave
it on for about a week and see where the oscillator is.  I will try to bring
it on frequency after it has been on for 24 - 48 hours then let it run.

I have 3 of these, all with Option 004 and we will see where they are at the
end of a week or so.

Joe

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Bruce Griffiths
Sent: Sunday, July 05, 2009 6:56 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Broken Ovenaire OSC 85-50


Pascal Nguyen wrote:
> Hi Joe
>
> Please open the link below
>
> http://www.airlab.com.au/nuts/joe_1.htm
>
> for an update of a simulated fault from an out of tune of the narrow 
> band pass filter
>
> Kind regards
>
> Pascal Nguyen
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to 
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> and follow the instructions there.
>
>   
Pascal

On a closer look your simulation has very little value at all. If one is
using an AC analysis its far more informative to open the feedback loop an
inject a signal to measure the loop gain and phase. One then has sufficient
information to determine if the oscillator has sufficient gain and an
aprpriate phase shift for oscillation to occur at a given frequency. Your
analysis injects an external signal whilst leaving the oscillator feedback
loop closed - not helpful or particularly useful at all.

If one wishes to simulate the actual output amplitude, then no extra source
is required with a good simulator the oscillator will oscillate and limit.
With the relatively low Q for the the crystal you have assumed the
oscillator will start and limit within a reasonable time without problems as
long as you dont use to short a minimum time step.

You have also assumed a fundamental crystal, an overtone crystal with a
somewaht higher ESR than 7 ohms is far more likely to have been used, but
without measuring the actual crystal one cannot be certain.

Bruce


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