[R-390] Adjusting Linearity Stack Collins PTO
Jim M.
[email protected]
Fri, 27 Dec 2002 23:05:11 -0500
Thanks much to all for the discussion of corrector stack adjustment on
the Collins PTO. It sounds formidable, but worth a try. I wonder what
would be the effect of just leaving the can off the PTO during
adjustment. Does the proximity of the can change the adjustment enough
to worry about? I have linearized a Cosmos PTO quite nicely
before...it's adjustment concept is a good one, it can all be done with
the unit sealed, and it comes out very linear indeed. Cosmos seems to
have taken a bad rap, but it does work well in my opinion. This Collins
PTO looks like a chore, but I want to keep my latest "Collins" 390a "all
Collins", so I will go for it and see what happens! 73 Jim N4BE
David Wise wrote:
>
> Shoot, I forgot another thing. If you let
> your thumbnails grow out a bit, if you
> hold the open PTO a certain way, you can
> push individual chips from side to side
> very precisely between them.
>
> 73,
> Dave Wise
>
> > -----Original Message-----
> > From: David Wise
> > Sent: Friday, December 27, 2002 3:18 PM
> > To: Dave or Debbie Metz; [email protected]
> > Subject: RE: [R-390] Adjusting Linearity Stack Collins PTO
> >
> >
> > I forgot to mention part of my procedure. I didn't
> > cut any holes. I took off the outer can and the oven.
> >
> > Warm it up a few hours.
> > Take data.
> > Power down.
> > Remove.
> > Disassemble.
> > Adjust.
> > Reassemble.
> > Replace.
> > Power up.
> >
> > Repeat until you're sick of it :-) I got mine to about
> > 100Hz, but that's down in the noise compared to endpoint
> > drift, and I doubt it's still that good.
> >
> > I got a Cosmos unit at a swap meet last summer. I'm
> > looking forward to getting into it sometime. It'll
> > be a breeze compared to the Collins.
> >
> > 73,
> > Dave Wise
> >
> > > -----Original Message-----
> > > From: Dave or Debbie Metz [mailto:[email protected]]
> > > Sent: Friday, December 27, 2002 3:01 PM
> > > To: [email protected]
> > > Subject: Re: [R-390] Adjusting Linearity Stack Collins PTO
> > >
> > >
> > > At 09:04 AM 12/27/2002 -0500, Jim M. wrote:
> > > >Thanks...I found this link, and also some references to
> > > Electric Radio
> > > >articles, doing a Google.com search (an amazing thig).
> > > Note: The PTO
> > > >alignment discussions on the r390a.com page appear to
> > > discuss only the
> > > >Cosmos manufactured PTO. The linearity adjustment for
> > > Collins mfgd PTOs
> > > >is considerabily different.
> > > >
> > > >http://groups.yahoo.com/group/r-390/message/4718
> > >
> > > Jim,
> > >
> > > Right you are on the difference between collins and Cosmos.
> > >
> > > A long time ago, I tried it and had limited success on a PTO
> > > that was out
> > > 6-8 kc with a procedure that went something like this:
> > >
> > > Take a junker PTO and cut a slit in the inner can above the
> > > camstack about
> > > a 1/4" wide to allow you to insert a piece of insulated
> > > something to push
> > > on the cam stack just above the roller. Then, adjust the
> > > tightening screw
> > > so that you can move the stack. First, you need to find the worst
> > > offset from end to end such that you are only going to push
> > > the stack down
> > > to either increase or decrease the freq. ( could never quite
> > > figure out the
> > > way to pull the stack up to go the opposite direction in
> > > frequency.) Then,
> > > mount the pto into the receiver with only the inner slotted
> > > can and push
> > > down at each 25khz increment to either raise (or lower, I
> > > cannot remember).
> > > the freq to the desired freq. I only used the inner can with
> > > the slit. This
> > > creates a bit of a problem because you have no rear mount so
> > > you have to
> > > brace it somehow. You should "T" in a counter to measure the
> > > freq with a
> > > counter. Remembering the PTO goes from 2.455--3.455 inversely
> > > as the freq
> > > is acending you need to set up a chart to know what is the
> > > desired PTO freq
> > > @ each 25khz indicated.
> > >
> > > I am sorry for the lack of detail but it's been a few years
> > > and I forgot
> > > the details. I am sure there must be a better way. However,
> > > I was not
> > > able to figure a way to adjust the camstack short of
> > pulling the PTO
> > > hundreds of times with a trial and error method. I seriously
> > > doubt that
> > > Collins did anything trial and error. I am so in awe of the
> > > engineering of
> > > this setup. What a sophisticated way to linearize a very
> > > delicate oscillator.
> > >
> > > I know that there has been a lot of talk about the PTO
> > > manufacturers here
> > > on the list but a long time ago I had a conversation with
> > > Paul Zechinno at
> > > Mil Spec Communications, (Not Rick Mish) and he was less than
> > > complimentary
> > > on Cosmos compared to the Collins PTO's. He had years of
> > > experience with
> > > these and felt that the Cosmos was probably fine when it left
> > > the factory
> > > but would not weather the years like the Collins units in the
> > > non A 390's.
> > >
> > > However, bottom line: Don't do it! If you have a PTO
> > > within one or two
> > > KC, you have NO problem. It never was perfect and I doubt
> > > seriously that
> > > you can achieve anything better.
> > >
> > > 73's
> > > dave
> > >
> > >
> > >
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> > >
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