alternately you could use a short-haul modem. I've used the ones from Telebyte running over with good success. you can get up to 115.2 kbps on ~1km of cable on some of them.
http://www.telebyteusa.com/shorthaulmodem.htm -eric On Mon, Nov 23, 2009 at 7:37 AM, Justin Pinnix <[email protected]> wrote: > Hi Rex, > > Sounds like a neat application. 100 meters might be a bit long for RS-232. > I was taught that 50 feet is the limit for 9600bps. You may need to use > RS-422 (balanced version of 232), low capacitance cable, or a lower baud > rate. Since you're a ham, you could also do it wirelessly over UHF packet. > You might even be able to use existing APRS hardware, provided it leaves you > enough significant digits. > > 73 de AJ4MJ > > On Sun, Nov 22, 2009 at 8:39 PM, Rex Moncur <[email protected]> wrote: > >> Given that we cannot do it with one GPS in a fixed position I would like to >> get people's ideas on whether there is a reasonable cost way (say less than >> $2K) to do it with two GPSs to get within a say half a degree. >> >> >> The application is to find azimuth headings for Amateur radio microwave or >> lightwave experiments. One cannot normally do star shots due to either day >> light or clouds. >> >> Let us assume that you can run the two GPS's over a baseline of 100 meters. >> At present I can get to within about plus/minus two degrees by walking an >> inexpensive handheld GPS over a baseline of 100 meters but I want to do >> better than that. For the hopefully more accurate measurement I would place >> one GPS and antenna at the microwave dish or lightwave transmitter and the >> other would be set up 100 meters away roughly in the direction one needed >> to >> beam. When a bearing was found one could either readjust the position of >> the >> remote GPS antenna to improve the accuracy or just allow for any error by >> beaming by this amount to the GPS unit. >> >> Let us assume that both GPS antennas are in a fixed location and the >> results can be averaged over say 30 minutes to improve the accuracy. I >> assume also that many of the errors due to propagation would cancel over >> such a short path. The data from both GPSs would be fed to a laptop over >> say RS232 line which I hope would work for 100 meters (perhaps 50 meters >> each way if necessary). The Laptop would have software to process that >> data >> and provide a bearing between the two antennas. Can anyone comment on: >> >> (a) the likely accuracy of such a system >> (b) whether there is any software out there that can do this. >> (c) the recommended GPS units for this application. >> (d) whether there is something one could purchase as a complete package at >> a >> reasonable cost (ie less than $2k) >> >> 73 Rex VK7MO >> >> >> >> >> >> -----Original Message----- >> From: [email protected] [mailto:[email protected]] On >> Behalf Of [email protected] >> Sent: Monday, 23 November 2009 8:08 AM >> To: time-nuts >> Subject: Re: [time-nuts] OT - GPS and North >> >> Thanks all. >> >> The conclusion seems to be that an ordinary and stationary GPS receiver >> with >> a single >> omnidiretional antenna knows very well where satellites are relative to the >> true North, >> and where the true North is relative to satellites, but doesn't know (more >> precisely: >> can't indicate, as it lacks another reference) where satellites or the >> North >> actually are. >> Eventually this appears quite obvious. >> >> Antonio I8IOV >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- --Eric _________________________________________ Eric Garner _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
