The gain of a LPDA should be mostly consistent across its designed frequency
of operation. If it's not, then there's a design error. So, I would
expect one gain figure +/- some amount of variation in dB across the design
spectrum.
Assuming L.B. Cebik's set of LPDA formulas are more accurate than what had
been used between 1960-2000, then this on-line calculator may be of
interest:
http://hamwaves.com/lpda/en/
I recently purchased a Tennadyne T14-HD. It was not purchased for its
published gain figure. Run through Cebik's formula and to achieve 8.5 dBd
(or 10.65 dBi) in free space from 30m-10m, you'll see a surprising result
when using optimum sigma and tau values.
If the AutoEZ interface to EZNec can easily generate an accurate LPDA model,
it would be worth validating against Cebik's work, although I have to
believe he cross-checked his own math with NEC since he was well known for
his NEC analysis.
Paul, W9AC
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
jcjacobsen@q.com
Sent: Tuesday, April 7, 2015 8:43 AM
To: jim@audiosystemsgroup.com
Cc: towertalk@contesting.com
Subject: Re: [TowerTalk] Antenna choices
Interesting topic. Jim was questioning the data on the Tennadyne LPDA
products.
<snip>
Yes, that's the real question. Part of that is to know the forward gain of
the T11. I see a single number for gain for an antenna that covers two
octaves of frequency. Somehow I don't trust that number on all bands. Also,
by the gain numbers (5.8 dBd, 7.94 dBi, 13.14 dBi @ 1 wavelength height)
>>>>>>>> I see an asterisk, but no note to go with
the asterisk. <<<<<<<<<
<done>
At the very bottom of the page for Original Tennadyne products is this
statement:
" *These gain figures are fictitious, but since other antenna manufacturers
tend to use them to manipulate things in their favor by enhancing their
specifications with phony data, we've added them so that you can get
accurate comparisons. "
I have no connection with Tennadynne or any other antenna manufacturer.
73
K9WN Jake
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