The B&W BWD90 is about 5-6dB down from a dipole on 40m and up and 80m
and down does suffer more loss that’s true. If there is room for the
180ft version it should have consistent performance down to 80m. If you
try to feed a mono band dipole with coax and an LDG tuner it will
probably have more loss on some bands than a T2FD and using a 4:1 balun
and balanced line is better with an LDG but it will not tune everywhere.
What’s worse, an antenna that will not reliably tune where you need it
or an antenna that will always work with some loss? You have to consider
the user in this case as someone who may not have the experience to
diddle with tuners or recognize when something is not working properly.
Not everyone can make reliable contacts with an FT-817, it requires
knowledge, patience and higher efficiency antennas. If it were up to me
to set up a fire station for regional comms, I would consider the 180ft
B&W, a simple to use HF rig and a solid state 500w amp which will make
up for the 5-6dB loss of the antenna over a dipole when necessary. And
that is assuming a resonant dipole at low height is my design goal.
Also, 1000’s of B&W T2FD type antennas in use right now working just
fine in military and government use for there intended purpose, which is
push the button and get the message through without messing around.
Bob


Eric wrote:
On Sat, 10 Feb 2007 08:35:55 -0800, Bob wrote:

To keep it simple, a T2FD type antenna would not require any
tuning or thought, just plug in and talk. B&W makes a commercial T2FD
style, model BWD-90. I know someone will chime in and say these are crap
but they work just fine and I believe a slight trade off in performance
for ease of use is paramount for the situation you describe.

Good morning, Bob.

Yeah, good luck with that.

T2FD antennas can exhibit as much as 17 db of loss while maintaining a
decent VSWR.

I have run communications tests with another amateur who lives one town
away. We have similar grounds, similar HAAT, and similar height AMSL. He
uses a B&W T2FD antenna (I believe it's the B&W-90) and I use a cut dipole
for 75 meters, at comparable heights (mine is 17 feet high and his is
something like 25 feet I think). He runs 100 watts and I run a grand
total of FIVE (5) watts with a Yaesu FT-817. I often get BETTER signal
reports on 75 meters than he does, from stations within about a 100 mile
radius of here.

I certainly wouldn't want a T2FD antenna for mission-critical use,
especially since for the price of a B&W, you could buy an auto-tuner from
LDG and have just about enough money left over to cover the materials for
a cut dipole.