Cecil Moore wrote in message ...
Brian Kelly wrote:
I've read the whole thread thru Tuesday AM, I get your point . .
. . . see if it's possible to cover that range with some
single specific length of ladderline and the two-section BC variable
cap? If yes I think you have a real keeper idea.

Maybe you'll like this one. 110 ft dipole at 40 ft, fed with 110 ft of
450 ohm ladder-line and tuned with a single control dual-gang variable cap,
i.e. no conventional antenna tuner.

.. . . OK but 110 feet of feedline to an antenna at 40 feet is a whole
lot of feedline to deal with under normal installation condx. At least
around here in suburbia.

Such an antenna system covers the entire
75-80m band with a 50 ohm SWR ranging from 1.7 at 3.5 MHz to 1.0 at 4.0 MHz,
according to EZNEC. Full band coverage at the twist of one knob? You likeie?

Sure do, could be extremely useful, I've moved it into my "idea book".
It's an easily tunable 80/75 variation on the similar antennas in your
website.

For a coax fed dipole, EZNEC reports an SWR=2:1 bandwidth of 170 kHz.

That's roughly what I get with with Nec-Win-Plus. If I make the dipole
131 feet long I get the following SWRs:

3.50 Mhz = 3.2
3.65 Mhz = 1.5 (curve min point)
3.80 Mhz = 3.5
4.00 Mhz = 4.7

So it's not possible to get much bandwidth across 80/75 with a simple
dipole without an ATU no matter how you diddle it. Then you're down to
a low-loss tuning scheme like you've come up with which in this case
is a complete no-brainer. IF one can figure out to what to do with all
the excess feedline without messing it up.

w3rv