Shalom ,
The airtronics 'vanguard' and possibly other
new Airtronics transmitters have
the two output wires from the round 5-pin connector reversed from the 'usual' which is what I call the plans listed at Ken Hewitt's website.
This caused jittery symptoms which are similar to those reported by others in this forum, possibly from different reasons.
TIP FOR NEWBIES ORDERING FROM KEN HEWITT
() The connector on back of the vanguard is called '5pin' even though it has six holes; the sixth 'case ground' is apparently not considered a pin. ???