[Elecraft] dBd vs dBi

[George, W5YR]

While I agree with the first part of Earl's statement quoted below, I
believe that under certain circumstances, ARRL will in fact publish gain
figures, etc.

The following is taken from the ARRL website:

"Antenna advertisements that specify gain, front-to-back ratio, or
beamwidth are acceptable if the antenna has been tested in accordance with
EIA Standard RS-329, Part 1,
and a statement to this effect appears in the advertisement. Certified test
results must be submitted with the ad. 

"In lieu of RS-329-certified results, the advertiser may advertise
performance figures derived from specific antenna modeling programs. To do
so, the advertiser should first
model the antenna, using either YO (Yagi Optimizer, for Yagis only) or the
latest version of the NEC (Numerical Electromagnetics Code) program. See
the ARRL Guideline
for Modeling Antennas for Advertising Acceptance for answers to frequently
asked questions and for sample graphs. The data files used must be
submitted to ARRL at the
time the advertisement is submitted. 

"All advertising performance claims derived from antenna modeling must
indicate that they are calculated. As a minimum, we expect to see the peak
free-space gain (in dBi
referenced to isotropic) at a manufacturer-specified frequency. ARRL
encourages advertisers to provide even more information to end-users,
showing performance
measurements or computations over a specified frequency range, rather that
at a single frequency. 

"In addition to free-space performance figures, advertisers may wish to
show computed performance over ground. If so, they must use a "typical"
ground, with a conductivity
of 5 mS/m and a dielectric constant of 13. They must invoke the
Sommerfeld/Norton ground model if NEC is used, and the terrain shall be
flat ground at antenna heights
specified by advertiser. 

"Advertisers may elect to show a computed front-to-back ratio at a
frequency they specify. However, ARRL encourages advertisers to show the
worst-case front-to-rear ratio,
over a frequency range of their choice, preferably a complete amateur band. 

"ARRL also encourages advertisers to grant permission to place modeling
files on the ARRL BBS for knowledgeable users to try for themselves, to
foster greater public
confidence in performance claims. As always, the ARRL Laboratory reserves
the right to inspect and test an actual antenna to verify modeling claims."

I am pleased to see ARRL adopt this enlightened policy regarding antenna
ads rather than avoiding the issue altogether. 

73/72, George    
Amateur Radio W5YR -  the Yellow Rose of Texas
In the 57th year and it just keeps getting better!
Fairview, TX 30 mi NE of Dallas in Collin county EM13qe
K2 #489      Icom IC-765 #2349     Icom IC-756 PRO  #2121



k6se@juno.com wrote:

> Be skeptical of any manufacturer's gain claims they give in their specs.
> Unscrupulous claims of antenna gain is why ARRL will not publish gain
> figures in QST ads.
> 
> Some claims are honest, while many are not.