Re: [TenTec] Corsair II PTO

[Dave Moorman <dmoorman4@comcast.net>]

On Dec 7, 2004, at 11:52 AM, Paul DeWitte K9OT wrote:

> My Corsair II will drift 4 or 500HZ until warmed up. Does a PTO 
> rebuild take care of this? Or do you do rebuilds just because of the 
> hard grease? I have no problem with the turning of the vfo just the 
> drift.

This may be within spec, Paul.  The manual says about VFO stability:

"Less than 15 Hz change per degree averaged over a 40 degree change 
from 70 to 110 degrees F after 30 minutes warmup."

This is not the plainest statement in the world, but it seems like what 
they are saying is that over a 30 minute warmup period, the temp in the 
VFO will climb from 70 F up to 110 F. During that warmup period, the 
frequency will change 15 Hz or less per degree F.  Assuming the worst 
case scenario of 15 Hz per degree, then the drift would be 15 x 40 = 
600 Hz.  So your 400 Hz to 500 Hz drift, being less than 600 Hz, would 
probably be in spec.

"Probably", because to really know this, you'd have to know the 
temperature of the VFO after 30 minutes of warmup.  If inside your 
Corsair II the temp only goes up to 90 F, that's only 20 degrees change 
and the allowable drift would be 300 Hz.  At any rate, you are pretty 
close to spec.

The other aspect of this situation is that the PTO rebuild, as I 
understand it, is a mechanical rebuild which corrects mechanical 
problems like backlash and slippage but would have no effect on warmup 
drift.

The other thing I'm curious about is - why is less than half a Hertz 
warmup drift a concern?  Digital modes?

Dave K9SW

Corsair 2
Argonaut 2
Scout

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