Serial RTCM3 test mode for EMC testing

Hi all,

I have a difficult question (i think). We have made a custom radio that fits the REACH RS2+ that can interface with our drone. This is a “dumb” radio that transmits the RTCM3 messages via 868MHz.

We want to test the basestation incl radio on locations where there is no GPS signal. Either indoors or in a faraday cage. Is there some way to get the serial output with “fake” messages so that we can test the radio anyway.

Also, before someone gives options like: “use a dummy serial like a PC or arduino”. That’s not really possible. Adding a larger cable or device to the test will skew the EMC test results too much. The radio is also powered via the REACH RS2+.

Thanks!

Hi @b.bruinsma,

Welcome to our Community Forum!

The RTCM3 messages require actual GNSS data, so generating “fake” messages without GNSS input it won’t be possible. Since you’re testing in an environment without a GPS signal, the RS2+ won’t be able to produce valid RTCM3 output to send the data via radio. Since this is such a custom setup, I’m not sure we can provide much help in this particular case.

Hi Victor,

Thanks for the quick reply. I was hoping there would be some kind of hidden feature or testmode available. Usually these testmodes are available in firmware for production to test outputs because GPS is usually also not available in factory halls.

Can I ask how the output is tested in your production facility? Perhaps I can mimic it. Maybe a GNSS repeater? Or special production firmware.

Currently, we don’t have a test mode or hidden feature for this kind of setup or a special firmware for production environments. The best way that we could advise you to test the outputs is through outdoor testing, since the receivers will not be able to output messages without any data.

But I have passed your suggestion on as a feature request to our development team.

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Do you need to test as 1 unit, or can you run a (long) cable between the radio and the RS2+, that can then reach the inside?

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Hi @wizprod

Great suggestion, but the the Emlid would still be inside a building. My solution now would be placing an L1 GNSS repeater behind the antenna.

Thanks for the replies anyway!

Not sure that would help you. The RS2+ requires a dual frequency (L1+L2) to work.

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