How can I test a GPS antenna

[cagey]

Reasonably confident that plotter is ok, taken home over winter and kept warm, dry etc. All the other systems on plotter work,radar,depth etc everything except GPS , have traced and visually checked the wiring between antenna and plotter and everything looks fine but no matter what I do the plotter won’t find itself. The antenna was new last year bought from “ Service Centre” who had completed a repair to plotter and replaced antenna because I’d lost the original .
Thanks for any help.
K

 

[PilotWolf]

Does it need a rough position Entering g somewhere so it has a clue where to look for satellites?

Does the antenna have a clear line of sight to the sky?

W.

 

[Jamie Dundee]

If the plotter has a built in GPS receiver try unplugging the external and see what happens.

 

[Rocksteadee]

Somewhere in a menu there should be a setup page that displays the number of signal from satellites and their strength.
it can take up to 15 mins to find itself if it’s internal almanacs has been off for a while and it is lost

 

[Stingo]

My new USB GPS took over an hour to find itself the first time I plugged it in. It now takes less than 30 seconds, which I assume is because it now knows roughly where is was last time it was fired up. Hope that sense some makes?

 

[lw395]

Reasonably confident that plotter is ok, taken home over winter and kept warm, dry etc. All the other systems on plotter work,radar,depth etc everything except GPS , have traced and visually checked the wiring between antenna and plotter and everything looks fine but no matter what I do the plotter won’t find itself. The antenna was new last year bought from “ Service Centre” who had completed a repair to plotter and replaced antenna because I’d lost the original .
Thanks for any help.
K

If it's a typical gps antenna with built in pre-amp, you can try it on another receiver, or try almost any other gps antenna with co-axial connection.
The amp in there is normally fed by about 5V on the centre pin of the coax. It should draw a few mA maybe in the range 5 to 20mA?

I have a magnetic gpsantenna from ebay, this is great for testing and cost not much. It needs to sit on about a square foot of metal to work at its best. You will want a coax adapter I expect, there are many different connectors in use, but if you get an SMA antenna, a 50ohm SMA to BNC fits many GPS receivers.

If the antenna has the whole receiver in it and a digital output, you can look for NMEA sentences with a serial to USB adaptor.

 

[Stingo]

My new USB GPS took over an hour to find itself the first time I plugged it in. It now takes less than 30 seconds, which I assume is because it now knows roughly where is was last time it was fired up. Hope that sense some makes?

I've since read that the last acquired position is the starting reference point eg the last time, date, lat & long are used to work out which satellites should be visible.

 

[Sandy]

Is there a screen that shows the position of the satellites? All GPSs I've use have had one. That will show you what "birds" the GPS can see.

If the system has been off for a while it can take up to an hour to write its own internal "almanac" of where the "birds" are.

 

[oldgit]

Purchased a aftermarket GPS receiver from Ebay to replace an ancient Raymarine 125 unit.
After about a year the replacement unit took ages to find even a single satellite .Sometimes failing completely .
Did all the usual checks.
Contacted the suppliers,who said no problem and simply sent me a new receiver FOC.
Connected and everthing instantly working as normal