Misposted this...
The taller the vertical section, the less top loading required. Therefore the
top portion does tend to be shorter. If you make the top longer, it may be
easier to tune the antenna from the base as the real resistance component is
raised somewhat and a capacitor would tune to resonance.
This would also provide a way to move from one end of the band to the other,
while maintaining a below 2:1 SWR, just by switching in or out the appropriate
caps.
You can put an inductor at the top. This presents other potential problems
like support issues, Q, power handling...
ON4UN covers this topic quite well in Low Band DXing and I recall seeing other
websites with specific instances. The ARRL has several articles from QST that
may be worth reading:
http://www.arrl.org/members-only/contests/results/2003/160-Meters/n0fp.html
and
http://www.arrl.org/members-only/contests/results/2003/160-Meters/n8mr.html
and
http://www.arrl.org/tis/info/Vertical-H.html
Most of us have less than ideal real estate to put Top Band antennas on, a
"Tee" will work, and work well, even if you don't have it "perfect". My top hat
is not close to being straight, the angles don't match from one side to the
other, it's in the trees, close to the house, short radials... All the bad
things, yet I've still managed to work 100 countries, WAS, close to WAS QRP
(read 5 watts) with KL7 and KH6 already in the bag, all with 100 watts or less.
It's really worth buying a copy of Low Band DXing and reading it. The National
Contest Journal also has had some great antenna articles in the past geared
towards the low bands.
Personally, I like KISS antennas. The top hat can be a pain, particularly in
trees, which is why I chose to make it bigger and tune from the base versus
trimming the top hat to resonance. I would use a longer top hat, if possible,
versus a coil/tophat combo. Less can go wrong and you'll pick up some
bandwidth.
Still, if that's the best option for the area, go for it.
Cheers,
Julius
n2wn
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