Chris Looked at the photos and believe you do not need a down converter. The one pix has a filter in it. dcf21r57. Its a murrata GPS bandpass filter 1575 MHz. So that indicates its looking for a antenna. See what voltage is on the antenna jack.
On Sat, Jul 20, 2019 at 9:58 PM paul swed <[email protected]> wrote: > Chris > What Bob was mentioning is true of the older units circa 1990s. I have > homebrewed down converters for two older units. Essentially everything gets > multiplexed onto the one jack so you can't really tell by looking if it > needs a downconverter or just an antenna. A bit of a hint. If there is > something like 12-15VDC on the jack then it needed a down converter. But > its just a hint not a rule. > Its funny how you find great receivers for $0 only to find out a key > component is missing. > Thats how I ended up with my Austron. > Good luck > Paul > WB8TSL > > On Sat, Jul 20, 2019 at 9:00 PM Chris Quayle <[email protected]> wrote: > >> Hi >> >> > It’s a pretty good guess that a device from that era ran a >> “downconverter” head end. >> > They had a full RF front end out at the antenna and fed some sort of IF >> frequency >> > back to the unit. Various outfits had approaches to how to do it. The >> net result is that >> > the head end is pretty specific to this or that box (or at least series >> of boxes). >> > >> > Since it’s an entirely different approach to getting things done, >> directly replacing the >> > head end with a modern module is going to be tough. The normal >> alternative is to >> > build up a downconverter. Some do it from scratch, others find a >> similar unit >> > somewhere and modify it to do the job. The big trick is to find out >> exactly what the >> > main box is looking for …. >> > >> > Bob >> >> >> I had wondered about that, but if you look at the antenna input, it >> looks like pretty high frequency, with a track inductor. Would >> assume that a downconverter from gps frequency would >> translate to baseband, but may be wrong. >> >> Took a few pics of the board, in case it looks familiar to >> anyone, but it must have been used on other, perhaps marine or >> avionics kit of the time. Problem is finding such an item, say >> on Ebay, without taking the lid off to verify contents. Have a >> feeling this quest may take some time :-). >> >> Here are the pics anyway: >> >> https://www.flickr.com/photos/182770787@N05/ >> >> Regards, >> >> Chris >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
