HiYa Jim,
   My name is Mike and I was just searching around on
google regarding the Par OA-50. Your site was the
first hit on the search page.  Just thought I'd give
you a report on the 2 OA-50's that I run. I run one on
mobile fed with RG/58 and driven by an ICOM 706MKII at
about 130 watts.  I am quite satisifed with the
results I've had with it.  I'm able to consistently
work stations 75-100 miles distant on sideband. It is
mounted on the back of my auto at a height of 6 ft
above the ground. I have the apex of the antenna
pointed to the front of the vehicle for safety
reasons.  I've not noticed a lot of directivity to the
antenna in my field test of doing 360 degree turns.  I
have good results on receive as well as transmit with
all stations I work.
  The other Par is mounted on the antenna mast at
about 35 feet up. It works superbly well.  I run an
Arrow 4 element yagi at 40 feet and use the par as a
receiving antenna.  I have a friend that runs an OA-50
on his Ford F-350 mounted on a tripod in the bed of
the truck up under the bed cover. It is about 4 feet
from the bed of the truck to the antenna feedpoint.
His works equally well and gets fantastic reports. His
other OA-50 is at 35 feet at his radio repair shop. We
have only one unfavorable comment on the antennas. 
They do detune with moisture. We have both noticed
detuning in the rain to the effect of about 100 kc's.
The the change is down the band. We've readjusted the
tuning to compensate for this. Mine is quite
broadbanded in dry conditions and I have useful
(1.5:1) VSWR for about 400 kc's.  I'll post you some
photos of my mobile installtion if you care to view
them.
  Just thought I'd give you a report of the success
we've had with ours and hope this helps someone else
along the way. All in all, we're impressed with the
antennas and have encourage others to purchase these
as well. If you have any questions or would like to
see the photos of mine, please feel free to contact me
and I'll gladly forward a few to you.  Thanks for
letting me offer up my opinion of this great antenna.
  See ya,
    Mike
      W4JMY

HiYa Jim,
  Here's the photos of the Par OA-50 on my Oldsmobile. My  friends have dubbed it 
the "Shrimpboat".
 Later, Mike W4JMY
 I forgot to mention that I also attached a length of 12# test fishing line to 
the apex of the antenna and secured it to an unused NMO mount on the roof to 
keep the end of the antenna stable in the wind.  I also suggest that you either 
tape or glue the black plastic form at the apex to keep it from sliding in/out.  
Also be sure to lock the elements in place at the base either by tape or push 
on star lockwashers to avoid slipping and detuning.
 I hope all of this is helpful to someone.  Enjoy the antenna if you get one.