From RinxeObsHeader.hpp:
waveFactValid = 0x0400, ///< "WAVELENGTH FACT L1/2"
and:
allValid211 = 0x080002FEB
So, the reader then requires a wavelength fact header line. This is incorrect as http://igscb.jpl.nasa.gov/igscb/data/format/rinex211.txt clearly says that line is optional.
This bug is in at least gpstk-2.0.src.tar.gz
This is fixed in /dev with rev 3344
It can easily be fixed in code by replacing line 149 of src/RinexObsHeader.hpp
allValid211 = 0x080002FEB
with
allValid211 = 0x080002BEB
and line 171 of src/Rinex3ObsHeader.hpp
allValid2 = 0x801607CB,
with
allValid2 = 0x801207CB,