Ditto on Bill's experience with the Bob Archer com antenna that I mounted
on my sidewall.  Mine sucks unless I'm within about 25-30 miles range. The
tail mounted one is adequate, but I still think I can do better.  I'll
eventually add a new com antenna, make it my #1 and change the tail to #2.
  In addition to the lousy performance of the com antenna, my Archer marker
beacon antenna (basically a copper strip) doesn't work at all and I had to
replace my Archer transponder antenna almost as soon as I started flying
when several ATC controllers reported my XPDR inop.  A check by a local
avionics shop showed that the Archer antenna (which is a flat plate that I
mounted in the tail) has huge dead spots to the front and rear.  When I
called Bob Archer to ask him about that, his response was, "Yeah, that
happens sometimes".  Not what I wanted to hear.
  So far my Archer NAV antenna seems to work OK, so I guess I lucked out
there based on what I've been hearing from other builders.
  My advice is to steer clear of Archer antennas if you have any good
alternative.
  Skip Slater
  N540ES