Hi Filtering is a good thing. Narrow filtering for GPS/L1 is the only way to get a GPSDO running on a cell site. There simply is way to much RF running around.
Once you head down the “triple band / all GNSS” road, the filtering needs to cover a *lot* of spectrum. Most setups simply drop the filtering from the equation. That’s true of home labs and fancier installations. My preferred approach is to use eBay / Minicircuits splitters with SMA connectors on them. They are dirt cheap and pretty much indestructible. A high gain survey antenna already has enough signal out to drive a rational length of LMR 400 and a fairly large splitter. More or less: Survey antenna has 50 db gain (eBay link does not work so I’m guessing here) Most modules / devices are happy with 20 to 30 db gain. They may only degrade a bit at 15 db. … You have 20 to 30 db to work with 8 port splitter is ~9 db 16 port splitter is ~12 db 100 feet of LMR 400 at 1.5 GHz is 5.9 db according to: https://www.timesmicrowave.com/calculator?Product=LMR-400&RunLength=100&Frequency=1500 <https://www.timesmicrowave.com/calculator?Product=LMR-400&RunLength=100&Frequency=1500> Worst case would be 20 db gain, 12 db splitter, 6 db coax. You still have 2 db to spare. Less coax or smaller splitter would give you a bit more margin. Bob > On Jun 2, 2021, at 12:20 AM, W7SLS <[email protected]> wrote: > > Hello, > > Looking for group wisdom to avoid newbie mistakes with a GPS splitter. > > For context, I’m a home- not National- or University-Lab. > That said, I have a non-zero budget. > > Today: > Antenna > 1- CORS RTK GNSS Survey Antenna high gain measurement GNSS GPS GLONASS > BDS <https://www.ebay.com/itm/253786590956> > 2 - patch antenna - works really well with Time Hat, even a few meters > way from window > > Splitter > 1 - Symmetricom 58536A > > Devices > 1 - Auction Site GPSDO > 2 - Leo Bodnar GPSDO > 3 - Time Hat <— wow! a fan! > 4 - (on the way) 2nd Time Hat > > Site > - suburban, forest to the S, hill to the N > > Challenge: > > Existing splitter is L1 only (I think), which blocks the many newer > GPS satellites. > With my compromised (for GPS) location, that’s not so good. > > I need / want a wider band GPS Splitter > > 1 - some posts talk about removing the bandpass filters in an existing > splitter > OK, but (a) it nukes any value of that splitter, and (b) those > filters also eliminate other interference (yes?) > > 2 - new choices seem to be in the $1000 and way above, outside of my > budget > > 3 - more interested in ‘ready to use’ than ‘have to add on bypasses' to > power the antenna (e.g., Cable TV splitter) > > 3 - auction site has numerous options, but I’m not sure how to > 'separate wheat from chaff’ > > LOL, some of you may be the sellers :) > > several items $500+ <— more than I want to spend > several items $30 - <— I’d rather not get aTV antenna > splitter and a hobby to make it work > > 324575653743 GPS Source S14 $175 > > 153359161105 GPS Antenna Splitter GPS/GLONASS L1 GALILEO E1 > BEIDOU B1- FedEx Fast Ship SV1AFN $120 > > > Thoughts? Thanks for the group bandwidth. > > Scott W7SLS > > PS: yes the Symmetricom 58536A will be for sale after I replace it. > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send an > email to [email protected] > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
