[50mhz] W5ZF comments

[Scott Townley]

My two cents (having been 'in the biz')

As a practical matter, measuring the gain of an antenna is probably easiest 
using a dipole reference.  Easy to construct the reference, well-known and 
repeatable pattern, used in practical working-class antennas.  I would 
guess that's where dBd really came from.

As computational power improved, and one could actually compute the 
double-integral of the far-field as required to find gain/directivity 
directly, perhaps dBi became entrenched as the analytical measure, since by 
definition that's what an analytical calculation would give.

I can tell you it's really confusing even among professionals.  Currently 
I'm in the cellular biz; the FCC rules and industry practices use dBd in 
the original (800MHz) cellular band, but use dBi in the PCS (1900MHz) 
band.  You have to be able to shift back and forth regularly.  Many's the 
time I have found (in my own work as well) 2.1 or 4.2dB errors because of 
dBd-dBi conversions.

Like most things, there is more than one way of thinking about 
it.  Becoming adept at both increases your reach :-)

At 19:36 2005-08-19, Chris Boone wrote:
>Correction,
>A dipole is 2.15dbi....not 2.8db
>
>Chris
>WB5ITT
> > -----Original Message-----
> > From: 50mhz-bounces at mailman.qth.net
> > [mailto:50mhz-bounces at mailman.qth.net] On Behalf Of
> > mweisbergs at juno.com
> > Sent: Friday, August 19, 2005 11:52 AM
> > To: 50mhz at mailman.qth.net
> > Subject: [50mhz] W5ZF comments
> >
> > Bravo, Stan - your memory is better than you're giving
> > yourself credit for. dbi may be of use to antenna engineers
> > but its use in ham dialogue is confusing at best. Yeah, the
> > dipole has 2.8 db gain over the non-existant isotropic but
> > has unity gain when regarded as the reference.
> > It seems that antenna discussions bring out the exuberent
> > imagination in folks; so much so that the ARRL has, for quite
> > some time, prohibited gain claims in the antenna display ads in QST.
> >
>
>Moderator: Ray Brown, KB0STN
>_______________________________________________
>50mhz mailing list
>Home: http://mailman.qth.net/mailman/listinfo/50mhz
>Help: http://mailman.qth.net/faq.htm
>Post: mailto:50mhz at mailman.qth.net