The SV6 has three different firmware versions for the following protocols: NMEA, TSIP, and TAIP. The latest Lady Heather code(5.01 or later) does support all the SV6 versions. You could pull the receiver and wire it to a TTL-RS232 converter and maybe get some more info on what it is doing. The SV6 NMEA firmware only uses around 3 of the NMEA messages. The TAIP firmware has a little more info available. The TSIP firmware has the most info available.