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