I can understand your concern about claiming a single gain spec for a
wide range of frequencies, but the ONLY practical gain spec for a real
world antenna is to spec it at a specific frequency ... and ... at some
specific height about ground, and of course flat ground is assumed.
There is nothing "specmanship" about identifying the height used in the
claim. Anyone who doesn't understand that terrain profile affects the
pattern probably shouldn't be spending that kind of money on an antenna.
Optibeam specs both frequency and height for each band, and will provide
EZNEC+ plots upon request. For what it may be worth, I own two Optibeam
antennas and found both the SWR curves and the azimuth pattern ...
measured with the help of a line-of-sight ham (K9RX when he still lived
in Arizona) about 30 miles away ... to be dead on the plots I was given
for both antennas. I had no way, of course, to measure absolute gain or
elevation pattern. I even generated my own EZNEC+ files based purely on
the element dimensions and essentially replicated the plots I had been sent.
Dave AB7E
On 4/7/2015 7:49 AM, Paul Christensen wrote:
"...actually I find that M2 is right on in their numbers – no specmanship here
whatsoever."
Then look here at the on-line M2 spec for their 12L LPDA model:
"Gain 6.8 dBi / 11.6 dBi @ 45'"
The gain is really 11.6 dBi at 45 ft. across the entire 30-10m spectrum? I can
see using one figure in free space, but not over earth.
Any manufacturer that implies gain at a specific height above ground, is using
"specmanship." At the very least, manufacturers should state: "modeled x.x MHz at
xx ft./m in height over flat earth. Changes in the surrounding terrain will affect this
specification." Also see Optibeam's advertising material for similar height/gain claims.
Paul, W9AC
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
StellarCAT
Sent: Tuesday, April 7, 2015 10:18 AM
To: tower
Subject: Re: [TowerTalk] Antenna choices
At the very bottom of the page for Original Tennadynne 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. "
73 K9WN Jake
...actually I find that M2 is right on in their numbers – no specmanship here whatsoever. Also Optibeam and Innovantennas
all use actual numbers from real modeling! I asked the owner of Tennadyne to provide actual modeled numbers – his reply
was to send an anecdotal note from a user glowing about how well it performed – to which I replied “you can find
this type of report for TA33’s... real hard data from modeling is what I need to know for comparison”... he
declined to provide it and wished me well. Nice enough guy – but no hard data to back it up.
Gary
K9RX
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