[R-390] Collins R 389 PTO

[DJED1 at aol.com]

Another PTO wouldn't work because of the 50 turn requirement, unless you  
geared it down.  But then the non-linearities would be 5 times worse.   
(Maybe that's better than a dead radio).
I thought about a DDS replacement for my R-390A, (it would be nice to get  
real 100 cycle readout accuracy) but the biggest stumbling block was the 
lack of  a 10,000 count encoder.  The best available seems to be 1026, and so 
that  throws you into dual encoders and a complex gear train.  But if you 
could  get it going then the mechanical dial and calibration would all still  
work.  The other issue is some way to remember the frequency setting with  
the power off- probably not a big issue.  The complexities of a  
microprocessor controlled DDS are beyond me, so I dropped the idea.  It  would be nice if 
someone would tackle the problem and share their results.
Ed  W2EMN 
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