Jim Higgins wrote:
On Sun, 16 May 2004 21:13:58 GMT, in
, R. David Steele
/OMEGA wrote:


http://www.bwantennas.com/

The military is using these antennas because of ALE (automatic
linking) and NVIS. I gather that while they are very broad
banded, they have less the best gain?

Any feed back?


I tend to compare the claims for any antenna to the
characteristics of a dummy load and then remember the principle
of reciprocity.

So for the BW dipole let's see. It's really quiet, esp on the
lower frequencies. It's really broad banded. It's not for me.


Doh! I guess that was your point!

- Mike KB3EIA -

Jack Twilley wrote in message ...

Out of curiosity, what other antenna provides a better cost-benefit
ratio while maintaining the same constraints with respect to power,
size, and construction?

A well made G5RV, for one. A well-made W3DZZ trap dipole, for another.
W5DXP's "linear tuner" dipole, for a third. Or the classic
dipole-with-openline-and-a-real-balanced-tuner for a fourth. All are
much more efficient than a T2FD of the same size.

The B&W/T2FD is discussed in detail on W4RNL's excellent site (which
see). In short, its efficiency is quite low on the lower bands and
gets to be almost as good as a halfwave dipole on the upper bands.
Their one and only advantage is low SWR over the frequency range.

73 de Jim, N2EY

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"N2EY" == N2EY writes:

N2EY Jack Twilley wrote in message
N2EY ...
Out of curiosity, what other antenna provides a better
cost-benefit ratio while maintaining the same constraints with
respect to power, size, and construction?

N2EY A well made G5RV, for one. A well-made W3DZZ trap dipole, for
N2EY another. W5DXP's "linear tuner" dipole, for a third. Or the
N2EY classic dipole-with-openline-and-a-real-balanced-tuner for a
N2EY fourth. All are much more efficient than a T2FD of the same
N2EY size.

The only one of those I haven't seen is the "linear tuner" dipole.

N2EY The B&W/T2FD is discussed in detail on W4RNL's excellent site
N2EY (which see). In short, its efficiency is quite low on the lower
N2EY bands and gets to be almost as good as a halfwave dipole on the
N2EY upper bands. Their one and only advantage is low SWR over the
N2EY frequency range.

I've looked, but the T2FD that's discussed isn't the one I'd be
buying, and I'm not sure if that matters.

N2EY 73 de Jim, N2EY

Jack.
- --
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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Jack Twilley wrote:
The only one of those I haven't seen is the "linear tuner" dipole.

It's described at: http://www.qsl.net/w5dxp/notuner.htm



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Jack Twilley wrote in message ...
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"N2EY" == N2EY writes:

N2EY Jack Twilley wrote in message
N2EY ...
Out of curiosity, what other antenna provides a better
cost-benefit ratio while maintaining the same constraints with
respect to power, size, and construction?

N2EY A well made G5RV, for one. A well-made W3DZZ trap dipole, for
N2EY another. W5DXP's "linear tuner" dipole, for a third. Or the
N2EY classic dipole-with-openline-and-a-real-balanced-tuner for a
N2EY fourth. All are much more efficient than a T2FD of the same
N2EY size.

The only one of those I haven't seen is the "linear tuner" dipole.

http://www.qsl.net/w5dxp/notuner.htm

N2EY The B&W/T2FD is discussed in detail on W4RNL's excellent site
N2EY (which see). In short, its efficiency is quite low on the lower
N2EY bands and gets to be almost as good as a halfwave dipole on the
N2EY upper bands. Their one and only advantage is low SWR over the
N2EY frequency range.

I've looked, but the T2FD that's discussed isn't the one I'd be
buying, and I'm not sure if that matters.

Which one would you be buying and how is it different? Most of the
data in the W4RNL site is for a 90' T2FD. When you look at the gain
curves, remember that they're in dBi. A simple halfwave dipole has
about 2.2 dBi gain.

The T2FD isn't a new invention - it was in QST about 1948 as a
*receiving* antenna, and that wasn't the first article on it by any
means. Government/military folks wanted a receiving antenna that was
essentially omnidirectional and would give a decent match to balanced
line over the HF frequency range - possibly feeding several receivers
via an active receive coupler. Low efficiency below 8 or 10 MHz was no
big deal because the receivers had lots of gain, and atmospheric noise
dominates in that part of the spectrum even with a poor antenna.

Transmitting is another issue.

If you want to spend the money for a T2FD, enjoy. But in the same
space (T2FDs are not small!) and for the same or less money you could
have a much more efficient transmitting antenna.

73 de Jim, N2EY

On Sun, 16 May 2004 21:13:58 GMT, R. David Steele
/OMEGA wrote:

http://www.bwantennas.com/

The military is using these antennas because of ALE (automatic
linking) and NVIS. I gather that while they are very broad
banded, they have less the best gain?

Any feed back?

I have used the BWD-90 for 2 months now, and love it.
I live on a city lot, and this antenna fits and performs better than
any other antenna I have tried. I've tried shortened 75m dipoles,
40 meter delta loops, and all kinds of slopers. all narrow banded and
loaded with city noise. The antenna has made the hobby fun for me
again. It is frequency agile, and has a great signal to noise ratio.
At 80 meters the antenna is only down 1 db from a standard dipole.
At 40 meters it even, there is 1db gain at 20 meters, and 3db at 10m.
(B & W,s numbers, not mine).
The botton line is if you live in the sticks with all kinds of space,
and no noise, you don't need a folded terminated dipole.
you can run wire to the cows come home,
but it's sure nice in the city.
Curt

Any feed back?

If you desire a single antenna with excellent SWR match at many bands, then I
am of the opinion that there is value here.

Even the most efficient horizontal dipole is almost useless for DX--the assumed
need, not NVIS-- unless it is high up. This is because all low dipoles have low
gain at low elevations: Their launch angle is quite high.

I would suspect that typical ohmic losses on the BW are 2-5 dB. The mismatch
lsses are negligible.

Getting this well over a wave high at the lowest freq of operation will afford
at least that, and probably more, in a gain differential at low angles,
compared to an efficient, low dipole.

The point: a high BW antenna will work well. Any low dipole will work poorly.
The in-between is a valid issue to ponder.

73,
Chip N1IR

"Fractenna" wrote in message
...
Any feed back?

If you desire a single antenna with excellent SWR match at many bands,
then I
am of the opinion that there is value here.

Even the most efficient horizontal dipole is almost useless for DX--the
assumed
need, not NVIS-- unless it is high up. This is because all low dipoles
have low
gain at low elevations: Their launch angle is quite high.

I would suspect that typical ohmic losses on the BW are 2-5 dB. The
mismatch
lsses are negligible.

Getting this well over a wave high at the lowest freq of operation will
afford
at least that, and probably more, in a gain differential at low angles,
compared to an efficient, low dipole.

The point: a high BW antenna will work well. Any low dipole will work
poorly.
The in-between is a valid issue to ponder.

73,
Chip N1IR

Chip, how did we digress to comparing a "high B&W" to a "low dipole"? When
the two are each at their optimal height (and why would we ever compare
anything else..) then the dipole has it all over a B&W. I use my (amost 1/2
wave height) dipole only for DX, without a tuner on it's two resonant
frequencies and with a tuner on two bands well above, with amazing results.
5, 8, 11 and 15 mhz to Alaska, Equador, Venezuela and Canadian Maritimes, if
that qualifies as "DX".

73

Jack Painter
Virginia Beach, Va

Chip, how did we digress to comparing a "high B&W" to a "low dipole"? When
the two are each at their optimal height (and why would we ever compare
anything else..) then the dipole has it all over a B&W. I use my (amost 1/2
wave height) dipole only for DX, without a tuner on it's two resonant
frequencies and with a tuner on two bands well above, with amazing results.
5, 8, 11 and 15 mhz to Alaska, Equador, Venezuela and Canadian Maritimes, if
that qualifies as "DX".

73

Jack Painter
Virginia Beach, Va


Hi Jack,

It seems relevant to me in two big contexts: (1) why do some folks do well
(relatively) with the BW antenna; (2) what does it replace?

My response clearly explains (1). In the case of (2), I can think of many
circumstances where it is preferable to put one dipole (BW) up high than a slew
of dipoles up high. If you have neighbors, you know what I mean:-)

Don't know what DX is to me anymore; I have DXCC #1 Honor Roll and haven't been
active on the low bands in several years. To someone else, DX is what you
haven't heard or worked yet:-) I say go for it.

Some folks don't live in a perfect world, Jack, and its good to know when a
compromise is a true degradation.

A BW antenna, up high, is a good antenna for DX across many bands. It is hardly
a dummy load.

Hope this helps on this question.

73,
Chip N1IR

With all the hoopla going on for this antenna I was surprised that no
one reported any calculated antenna efficiencies. So I modeled the
antenna in free space - to remove environmental influences other than
those contained within the antenna itself (terminating resistor and
wire loss) - NEC reported the following:

Freq. MHz. Efficiency Average Gain Peak Gain
MHz % DBi DBi

3.5 9.6 -10.43 -8.49
7.15 41.24 -3.85 -1.33
14.2 23.21 -6.36 -1.59
21.2 30.01 -5.23 -1.36
29 53.81 -2.69 2.17

73
Danny, K6MHE