From: caveat-lector@cox.net
"default" wrote in message
news:1213400540_8606@isp.n...
>
> On Thu, 12 Jun 2008 13:07:45 -0700, GeoSound
> wrote:
>
>>Am thinking about building an electronic sextant that would provide near
>>centimeter accuracy. This would mean a degree should be partitioned to
>>about 400,000 steps. Was considering using a pot and 5v to feed an A/D
>>but on reflection think that a single turn pot would not be clean enough
>>for that many steps. Would someone confirm this for me. Use of a
>>multi-turn pot requires gears which would be too expensive due to their
>>very critical meshing needed. Thanx, Ron
>
> Another idea - a old time variable capacitor. The position of the
> knob is directly proportional to the capacity
Not always true.
- and that can easily be
> resolved into a lot of counts by counting an oscillator's frequency.
>
> Look into VFO ("variable frequency oscillator") amateur radio
> operators use them in home built receivers - and they have various
> schemes for digitizing the outputs.
> --
The problem with a variable capacitor is that it can "drift" with
temperature and humidity changes.
Many years ago,1990's, I worked for a company that produced LORAN-C
receivers and they could, in the experimental models for the military,
locate you to within a foot or less if they could tune in 20 to 30 towers
but I have never heard of anything available to the public that can locate
you to within a centimeter. At that, they used state-of-the-art Cesium clock
generators and racks of clasified high-tech stuff. But, then I was never
allowed in to the section of the building where the government security
cleared Ph D's worked.
I don't believe that you can create a device that will, reliably, position
you to within a cm or two from simple publically available components, be it
GPS, LORAN or Sextant.
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
|
