Testing signal from GPS aerial

[Heckler]

In practice, an analogue multimeter on an NMEA signal tends to show a fairly distinctive swinging pattern. You're right that we wouldn't be able to see the transitions between individual bits at 4800 of them per second, so I assume this is the gaps between sentences.

Pete

In practice I have also found my digital voltmeter shows a "swing" on the screen when connected to nmea so that you can see if it is outputting. If you are really clever and connect the signal to a 9 pin serial port plug and plug it in to your computer serial port it will show up in Telnet
Stu

 

[skyflyer]

It started to exhibit different behaviour yesterday which makes me think it is the GPS antenna rather than the plotter; Ever so briefly it would flick to a Lat Long of N00 00.00 E000 00.00 and then back to the actual location. I guess it could be a loose connection still, but previously it show No Fix when that happened not the wrong Lat long; Anyway I will test it all as suggested. thanks everyone for the advice and expertise.

 

[lw395]

In practice I have also found my digital voltmeter shows a "swing" on the screen when connected to nmea so that you can see if it is outputting. If you are really clever and connect the signal to a 9 pin serial port plug and plug it in to your computer serial port it will show up in Telnet
Stu

It's not that hard to wire into an rs232-usb adaptor.

A good multimeter will have an AC setting to indicate the swing on the signal ignoring the DC.
Some cheap ones will just rectify the DC.