RE: NEC-LIST: Small antennas: can they me multiply resonant?

Chip

I have not seen any gain measurements for fractal antennas so cannot comment
on validity or otherwise. But I would characterise a traceable measurement
as one in which the quantities are measured with instruments whose
calibration is traceable to an international standard by an established
quality control procedure.

In professional antenna engineering the strategy is to feed a measured
amount of rf power to the antenna and to measure the radiated field (power
density) at a set of points around the antenna, sufficient to calculate the
total radiated power. Then the gain is equal to the directivity (i.e. the
pattern gain) less the efficiency factor, and the efficiency is the radiated
power divided by the power accepted at the terminals. Gain can be measured
within about 0.5dB above 1GHz and about 1-2dB below 30MHz by this approach.

Antenna measurements techniques are summarised in "IEEE standard test
procedures for antennas", ANSI/IEEE Std 149-1979, and the terms used
internationally are defined in "IEEE standard definitions of terms for
antennas", IEEE Std 145-1993.

Anyone offering a new antenna for general acceptance has a good chance of
success if the gain and efficiency are measured to professional standards.
I don't know if this has been done for fractal antennas in particular so
maybe you could point me to some references.

All the best,

Alan

-----Original Message-----
From: Fractenna_at_aol.com [mailto:Fractenna_at_aol.com]
Sent: 08 January 2003 14:21
To: nec-list_at_gweep.ca
Subject: Re: NEC-LIST: Small antennas: can they me multiply resonant?

In a message dated 1/8/03 8:59:48 AM Eastern Standard Time,
dbmiron_at_paulbunyan.net writes:

>
> Alan,
>
> No, I haven't seen any valid gain measurements published or otherwise
> for...fractal antennas

Hi Doug and Alan,

I just saw Doug's lengthy attachment sent to this open list. Was this meant

to be public?

That's very interesting. In the case of fractal antennas, could you kindly
help us out and cite 'invalid' published gain measurements, or tell us what

you have seen at all? I get the impression you may not have seen anything,
or
that the measurements lack validity in your opinion. Appreciate it if you
could clarify this for the group, otherwise it makes it look like many, many

researchers--myself especially--have been remiss and published 'invalid'
results.

Also, Alan, I don't seem to recall seeing your posts on this list which are
quoted here by Doug. What do you mean by "accurate and traceable gain
measurements" for fractal antennas? Are the published results inaccurate and

untraceable? Please clarify. That is the right thing for a scientist to do
in
a public forum, if the comments are so presented. These comments are so
presented now as public.

And Doug, if they are "invalid", could you please say why they are so?

I think the list would benefit from knowledge here on this interesting issue

and may benefit from sharing your perspectives if shown why.

Otherwise, I would appreciate it if you would clarify what you mean by
"valid".

Many thanks!

73,
Chip N1IR

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