Background: Without both code and carrier data, RTK and PPP navigation methods are not possible. While it is routine to have both (as well as other signals) in better modules and chips, some very low end chip sets do not provide a carrier output. This basically kills any ability to use such a chip set for RTK or PPP style navigation. Avoid them if you need sub-meter accuracy. If you look at the RINEX files for any system you can easily tell if carrier data is present.
Hint: RINEX, or the Receiver Independent Exchange Format,is the preferred human readable data interchange format used to exchange various types of GNSS measurements.
The carrier field in any RINEX file is the “L” (as in L1 or L2 etc.), if you do not see that field in the file header then you do not have carrier data. The code (pseudorange) is the C, Doppler is D (not found in all systems) and S is the SNR (C over No). Most converter tools have some options to suppress unused fields, so check to make sure the convert step did not removed the carrier data by mistake.
Below is a fragment from a uBlox 6T (an L1 only device) for one epoch (one measurement set).
The first 4 lines are part of the file header and serve to lay out the format of the data to follow in the file (this is fixed for the entire file). The next line is the time stamp of the measurement epoch (accurate to ~100nS). It also tells us that 12 more lines will follow for the 12 SVs that have measurements at that time and then enumerates the order of the SVs (which can change with each measurement epoch). This is a version 2 file style; version 3 differs in some ways.
There is code, carrier, Doppler and and SNR for all of these measurements but for one. You can see that the carrier for SV “G20” was missing in this data set. The RINEX format allows blank spaces to stand in for zeros. FYI about this SV: One can also see that this SV was low on the horizon and dropping out of view as the high negative Doppler rate and low SNR shows, which is the typical time carrier tracking is lost.
4 C1 L1 D1 S1 # / TYPES OF OBSERV 2016 6 7 17 42 46.0000781 GPS TIME OF FIRST OBS 2016 6 7 18 3 27.0000781 GPS TIME OF LAST OBS END OF HEADER 16 6 7 17 42 46.0000781 0 12G 7G 8G26G20G21G15G16G27G18G10S20G 4 24315075.481 127776517.3292 448.410 29.000 22629267.575 118917537.1101 2271.698 32.000 21895722.936 115062756.905 -3156.582 42.000 25179786.705 -3549.886 20.000 23308387.593 122486312.002 -2759.055 46.000 25514482.824 134079506.961 333.453 33.000 20601440.208 108261249.8101 -1454.798 43.000 20620768.706 108362926.6981 797.603 40.000 22056801.307 115909274.4371 -833.425 46.000 21617601.357 113601266.278 1698.172 47.000 37871568.996 199016439.7911 -286.053 29.000 23186586.975 121846252.716 -3871.296 40.000