On Tue, 21 Nov 2006 22:10:19 -0800, Richard Clark wrote:

By turns, you've painted yourself into a corner when we add up this
wish list. Worse yet is the complaint you anticipate with:
If I can't keep the efficiency above 50 percent across the range, then it
probably isn't going to be worth doing.

When you lead with your chin with:
It cannot use any sort of antenna tuner
this simply breaks the camel's back. Also, come to terms with there
is also no such thing as a miracle BalUn.

Good morning, Richard.

I was hoping to mitigate all of that by restricting the frequency range.
I'm not asking for 1.8-30 or even 4-30, but 4-9.

Can a T2FD antenna not be made 50 percent efficient across that restricted
frequency range?

The 50 percent efficiency floor is somewhat arbitrary but is driven by the
fact that some of the users of this antenna are going to be using power
levels as low as 5 watts. That's hard enough to do with a cut NVIS
dipole, without throwing an inefficient antenna into the mix.

The inability to use a tuner is driven by the fact that eventually, these
antennas are going to need to be usable with ALE radios. I don't know
very much about ALE (yet) but I have a hard time imagining an autotuner
that is consistently fast enough to use with ALE. Also, the users of these
antennas are, like me, going to be paying for them out of their pockets.
Few if any of the potential users that I know of today can afford to buy
an autotuner. I know I can't.

If it can't be done, then it can't be done. I'm realistic enough to
accept that and move on to something else, or drop the idea. It just
seems to me that within the limited frequency range, something like that
should be possible with the right choice of design parameters.