[R-390] Collins R 389 PTO

[Paul Anderson]

A quick search for "high resolution shaft encoder" shows numerous hits
for far higher resolution than 256 units per revolution.  Check out
what the computer controlled telescope guys are doing, for example.

I think a <$500 per unit cost could be achieved, exclusive of design time.

Paul

On Sun, May 3, 2009 at 9:18 AM, Mark Huss <mhuss1 at bellatlantic.net> wrote:
> There are several DDS (Direct Digital Synth) VCO kits running around,
> mostly based on the AD9850 or AD9851, for a hundred dollars or so.  With
> a range of 0-40+ MHz, it would be ideal.  The issue is the encoding.
> The PTO  covers 1.06 MHz in 10.6 turns, or 100 kHz in one turn.  To get
> 10 Hz resolution, you would need to have an encoder capable of a
> resolution of 10,000 per revolution.  256 is about the highest
> resolution available, which means you will need to drive at least two of
> them, with a 40 to one reduction between them.  Or alternately, drive
> two 128 state encoders with the second  advancing every  complete turn
> of the first.  A third, and probably most  practical, is a 256 encoder
> with a 40:1 reducer on the  shaft, and a reset button to zero it at '000'.
> I have considered a ten-turn pot coupled to a 16-bit A/D converter.
> Deriving both the A/D Reference voltage and the voltage across the pot
> from a single source may stabilize it enough to be practical.
> Unfortunately, you actually need an 11 turn pot to account for the
> overrun in the tuning (10.6 turns end to end).  Next, you will have to
> calibrate it for non-linearity, easily enough done through a table and
> interpolation.  And finally, add a thermistor to temperature compensate
> the 20ppm temperature drift of the potentiometer.  The problem here is
> that the cost would be more than a whole R-389/R-390/R-390A on the market.
>
> mparkinson1 wrote:
>> Hey guys I am looking for a PTO for a Collin R 389 receiver working or
>> not please I need one my receiver please email me off the list
>> mparkinson1 at socal.rr.com thanks.
>> Let me what you have and for how much even a junker R 389 would work
>> for me with the PTO intack thanks.
>> Matt Parkinson Military Equipment & R 390A Depot Center
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>
>
> mparkinson1 wrote:
>> Hey guys I am looking for a PTO for a Collin R 389 receiver working or not please I need one my receiver please email me off the list mparkinson1 at socal.rr.com thanks.
>> Let me what you have and for how much even a junker R 389 would work for me with the PTO intack thanks.
>> Matt Parkinson Military Equipment & R 390A Depot Center
>> ______________________________________________________________
>> R-390 mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>> Help: http://mailman.qth.net/mmfaq.htm
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>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
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>>
>
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