89 200tqw antenna

[Larry Mittell <lmittel@ibm.net>]

I have a non-Bose stereo in my 89 200tqw.  My AM reception goes away when
it rains or when my car is washed.  It seems to me that the prime suspect
is the short little roof-mounted whip antenna, since it's about the only
thing  water could get to.  The question is this-- do I have a faulty
antenna, or just poor sealing at the roof/antenna base interface?  If it's
the latter, perhaps I could inject some silicone sealant under the rubber
gasket.

If it's the former and I need to replace the antenna, does anyone know of a
source that supplies it at a reasonable price?  Didi at Carlsen said the
list price is about $280.  I didn't ask what the discount price was,
because I'm sure it would have been more than I'd *like* to pay.  (Sudden
thought-- are VW roof antennas interchangeable with mine?)

BTW, the windshield antenna is not hooked to the head unit.  Further, there
is no likely-looking cable in the vicinity of the head unit.  The former
owner says that this is the case on all Anvants of like vintage.  True?

While we're at it-- does anyone have suggestions for head unit/speaker/amp
upgrades costing less than an arm or a leg?  I don't need top-of-the-line
quality, but I would like to improve on what I've got.  I'd also like the
installation to have stock appearance (except for the head unit, of course)
insofar as practical.

TIA, 
Larry Mittell