[R-390] PTO end point adjustment

[Barry]

With the PTO out, I use one of the straight edges of the "slat" on the Oldham coupler and something like a T-Square that will "lock" the coupler in a vertical position.  I have a precision 45-45-90 square that I made when I worked in the machine shop that works well for this but other tools would work fine.

Starting at one end, I take note of the frequency (as seen on the counter), crank out ten turns, and re-lock the coupler's slat against the square.  The frequency at that point should be the initial frequency +/- 1000kc (depending on which way you're turning the shaft.  For example, one end might be 2.460 so the other end should be 3.460, etc.  While the exact end points will be 2.455 and 3.455 once you reinstall the PTO and synchronize it properly, it gets an overall 1000kc spread that is very close to the actual endpoint values.

Of course, if you were to use frequencies that are too far from the true end points, then there could be enough error to matter (and you might damage the PTO in the process), but I've not had any problems using this method.

Thanks,
Barry - N4BUQ

----- Original Message -----
> From: "Jacques Fortin" <jacques.f at videotron.ca>
> To: "Jordan Arndt" <Outposter30 at shaw.ca>, "R-390 Mailing List" <r-390 at mailman.qth.net>
> Sent: Friday, November 8, 2024 2:03:02 PM
> Subject: Re: [R-390] PTO end point adjustment

> Hi Jordan,
> 
> Y2K-R3, page 6-20 !
> You zero-beat at 7+000 then goes down to 7.000 and adjust end point in PTO
> for zero beat.
> Up to 7+000 and re-zero beat with the BFO only.
> Back to 7.000 and re-zero beat with the end point, and loop again.
> Both ends sold be aligned after few iterations.
> 
> But I neve aligned my PTO when they were IN the frame...
> I used an external supply, frequency counter and the alignment dial:
> Set PTO output to exactly 2.455MHz (almost fully clockwise) note the
> position on the alignment dial.
> Go back (counter-clockwise) exactly 10 turns to same alignment dial
> position.
> Set output to 3.455MHz exactly using the end point adjustment.
> Go up (clockwise) to 2.455 MHz exactly: expect dial reading change and take
> note of the new reading.
> Go back again 10 turns to this new dial reading.
> Set output again to 3.455MHz exactly using the end point adjustment.
> Loop again a couple of times: the two ends will converge to the same reading
> after few iterations.
> Once the end points give the same dial readings, re-install the PTO in the
> receiver with dial at 7+000 and PTO at 2.455 MHz positions.
> Check operation.
> 
> 73, Jacques, VE2JFE in Montreal
> 
> -----Message d'origine-----
> De : r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> De la
> part de Jordan Arndt
> Envoyé : 8 novembre 2024 14:13
> À : r-390 at mailman.qth.net
> Objet : [R-390] PTO end point adjustment
> 
> 
>    It's been a long time since I had to adjust PTO end points and I need
> some advice as to the best method.
>    Do I adjust the coil at the -000 end after setting the +000 end with the
> zero adjust or vice-versa..?
>    Help...73...Jordan VE6ZT
> 
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