"The SA-008 in the vert stab uses RG58 lead in coax,
the other uses the newer RG400.
The problem is the SA-008 in the vert stab produces a weak
signal as reported by the controllers. If I switch the antenna
between com1 & com2 the problem moves with the antenna."
Leon,
RG58 is not higher impedance than RG400; they are both 50
ohms. RG58 has a little more loss than RG400, but unless you're running
through 100 feet or more it shouldn't make that much difference.
However, if both radios work well when connected to the SA-006 but both are
reported as sounding weak when connected to the SA-008 then it sounds like there
is a problem with the coax, the antenna, or the connection between the
two. If you can get someone to run a VSWR check on it you
can tell if there is an impedance mis-match problem, but it may not
tell you if there is a lossy connection somewhere. An antenna tip worth
reading from Bob Archer can be found at
Tom Gourley