"The full A, B, L, R applies to the receivers that take 3 or 4 satellites.
They refer nominally to the antenna position.
A and B are the two top sockets on each side in a receiver with no internal antenna or A is the internal antenna and B is the first satellite socket.
L and R are the additional satellite sockets- the bottom ones on the left and right.
If you have a receiver that takes only one satellite then only A and B are seen. "
Took awhile to find it, but here's the link:
https://www.rcgroups.com/forums/showthread.php?2542818-Spektrum-Telemetry-Log-Viewer-%28one-more%29/page27#post39048967Hope this helps.