[time-nuts] SE880 GPSDO

Bruce Griffiths bruce.griffiths at xtra.co.nz
Thu Apr 28 21:11:11 EDT 2016


One advantage of a free space optical link for this application, is that most of the factors that produce severe attenuation of the optical signal also preclude observation of the stellar sources as well. Thus the link only needs to work well under near ideal conditions.Increasing the aperture of the transmit and receive optics reduces the required transmitter power and the associated safety hazards of the transmitted optical beam.
Bruce
 

    On Friday, 29 April 2016 1:02 PM, Bruce Griffiths <bruce.griffiths at xtra..co.nz> wrote:
 

 If you add a small beam expander, then there should be few safety issues.In this case a laser beam power of a few (1??) mW may suffice.Similar collection optics at the receiver will also be required. One can use small telescopes for this purpose. I've used an eyepiece with a 12" (305mm) dobsonian to produce a 300mm diameter beam from a green laser pointer. You shouldn't need to go quite that far though.
Bruce
  

    On Friday, 29 April 2016 12:01 PM, Attila Kinali <attila at kinali.ch> wrote:
 

 On Thu, 28 Apr 2016 23:22:24 +0200
Attila Kinali <attila at kinali.ch> wrote:

> > Thanks Attila, I know how to build a transmitter and a receiver, and now 
> > is more clear the system you designed. But as I will propose this system 
> > to an astro club, and in this astro club there's the possibility that 
> > not all would have a radio license, I need something "free-to-play", if 
> > it concern.
> 
> Ok.. that's quite some constraint. This rules out any kind of transmission.


Here another crazy idea:

If you can ensure line of sight between stations, you can use a
laser link between them. Modulate the laser with an RF signal in the
10-100MHz range. Use this on the receiver side to lock the OCXO.
Proceed as before...

This approach should be fairly simple to build, but needs some care
to ensure that you are not endangering anyone with the laser beam.
Other than that, you don't need a license for running such a system.
There have been hobbyist laser communication links around for a couple
of years, though i would advise to check the designs carfully as some
of them have EMI and other problems that the original designers and users
didn't care about.


            Attila Kinali


-- 
Reading can seriously damage your ignorance.
        -- unknown
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