[Mobile-Portable] New car and considering new antenna setup! Followup

[David E. Shelton]

Thanks to so many that replied to the post. I have still not decided =
what to
install but I am leaning heavily towards another Screwdriver antenna,
probably the Hi Q brand as its construction is far better than the rest =
of
the screwdrivers out there. I do know from practical experience that the
larger the coils, the higher the Q, and in general larger physical size =
is
an advantage over smaller antennas whether center loaded or top loaded. =
This
puts the advantage in the screwdriver's favor and if you add a =
capacitance
hat of any size there is less need for the coil, giving the antenna =
better
physical characteristics. Another thing that no one mentioned the =
loading
resistance of the antenna, 0 ohms is best most should agree on this,
screwdriver antennas have low impedance at the feed point typically =
around
0-10 ohms. The diamond and comet are at 50-52 ohms when tuned properly. =
Yes
the screwdrivers typically have a transformer that is used to match the
rig's feed line needs 50 ohms to the antenna, say 6 ohms with an 8:1
transformer that's 48 ohms matched at resonance. I again must say I like =
the
diamond/comet's lack of moving parts this is the weak link in the
screwdrivers design and also the advantage it has. Very nice to be =
driving
down the road and change bands and portions of the same band without
utilizing a tuner or getting out of the car, but with motorized antennas
comes reliability issues. I am glad to be back on this list/reflector, =
it
has been a long time since I read or participated here, thanks again to =
you
all!

David E. Shelton, RN
david.shelton@louisville.edu
n4in@arrl.net