Bob,
You might consider using a marine fiberglass HF whip antenna (Shakesphere
makes a nice 23' job) fed with an automatic coupler (such as the SGC) at
the roof. You'd still have to install a counterpoise but you'd have an
optimum all-band installation that is light and built to last.
These antennas stand up well to wind, water and abuse (well, you CAN
break them if you tangle them up in enough mooring lines ... but that's
another story).
I'd recommend against stuffing anything in the bathroom vent stack ...
kinda defeats it's purpose. Further, you're going to put a great deal of
stress on the roof seal AND the vent stack, and you really don't want to
let water in to rot the roof and attic.
An alternative to a roof tripod would be to mount a pair of eaves
brackets on the side of the house and mount the antenna to that. Bring
the coax inside the attic (but have the coupler mounted outside), and
drop an identical length of wire down the side of the house for an
elevated vertical dipole.
***
Having installed a 35' marine whip on the top of an all-metal aircraft
hanger many years ago, I can speak well of the advantages of a nice big
groundplane. The antenna was mounted on a 6" pipe welded to the ridge
beam with the coupler directly below the whip. Performance with only a
couple of watts (blew the output module on a brand new transceiver right
out of the box ... again, another story) was better than with the
previous installation using a 400 transmitter and a random wire.
Best thing I can say about using a base tuned whip is the low profile,
very few mechanical issues, and simple operation. The coupler will set
you back some ... though there was a nice article in QST last year on
building your own.
Good luck with the new installation.
73,
Rick, WB3EXR
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