According to this, http://www.nist.gov/manuscript-publication-search.cfm?pub_id=912449
there are many practical challenges with a one way free-space optical link. They were, however, aiming for much higher stability than is needed here. There are a lot of ideas being tossed around here. It would probably help to focus the discussion a bit if we knew: (1) The budget (presumably small) (2) Site constraints - is there line of sight, is it really impossible to run a fibre (I know trenching costs are high but a fibre strung along a fence with some UV protection might be acceptable in this application) (3) What expertise there is that can be drawn upon Cheers Michael On Fri, Apr 29, 2016 at 11:11 AM, Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > 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.griffi...@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 <att...@kinali.ch> wrote: > > > On Thu, 28 Apr 2016 23:22:24 +0200 > Attila Kinali <att...@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 > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
