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Old November 22nd 06, 06:10 AM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Jul 2006
Posts: 2,951
Default Questions on broadband antenna design (e.g. T2FD)

On Tue, 21 Nov 2006 23:15:44 -0500, "C. J. Clegg"
wrote:

Yeah, this is exactly what I'm trying to avoid, by careful choice of
design parameters like length, resistor value, balun type. Feeding the
antenna with 100 watts and having all 100 of those watts dissipated in the
resistor, at any frequency within my range of 4 to 9, isn't going to work.


Hi OM,

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.


3dB is hardly they abyss of performance, and, in fact, you would
probably be hard pressed to notice it. If you could, your dream
antenna (for the price you are willing to pay) would automatically
qualify for the dung-heap.

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.

In traditional engineering, there is the adage that a well defined
problem contains its own answer. You can reconcile facing abject
failure by falling back and building a cost/benefit analysis of all
the characteristics of your desired antenna. It should take more than
half an hour to come up with the price tag. You may also discover
that you can live without some of those restrictions and you might be
able to live with a tuner - generations have survived and flourished
under similar circumstances.

73's
Richard Clark, KB7QHC
 
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