On 13 Feb, 20:34, "Tom Donaly" wrote:
art wrote:
My present antenna, which is for 160m and above, is about the size of
two shoe
boxes and is less than 2:1 swr (50 ohm) across the band when
situatedat the
*top of my tower.
I have googled a lot over the last month or so to determine if there
has been
claims for the 'smallest' transmitting antenna and what the criteria
consisted of.
If I knew what it was I would concentrate on making my antenna smaller
to reflect
something more close to point radiation which has been theorized as
being possible.
Seems like that there is no real definition of what a 'small' compact
antenna
actually comprises of *together with power handling capabilities!
*True, for receiving only there are many contestants all with
different criteria,
but for the ham community there is absolutely nothing for anybody to
compare
*with other than such claims as 'mine is the smallest and I work
anything I can
*hear' !. Can anybody point to a transmitting antenna that can be
considered
*'small ' *without the need for a ground plane, which thus puts *it
into the
*'antenna systems' *class ?
For a point of interest, I am presently using a reflector made from a
garbage can lid,
but it is not acting in anyway a dish antenna works when the reflector
is grounded!
As an aside, most posters to the group are aware that a modest sum was
offered
who could disprove my claim but with no takers. So can we put that
particular subject
*aside and concentrate only on the request of this posting which
should cut off
most of the insults ?
Best regards to all
Art Unwin

Hi Art,
* * * * *Get a copy of Balanis' _Antenna Theory, Analysis and Design_,
second edition, and read section 11.5, Fundamental Limits of
Electrically Small Antennas. Also, in the _Antenna Engineering
Handbook_, third edition, read section 6, Small Antennas by Harold A.
Wheeler. I won't vouch for any of the information, but it should give
you some ideas on what the practical limits of small antennas are
supposed to be by reputable people who have thought the subject
through.
73,
Tom Donaly, KA6RUH- Hide quoted text -

- Show quoted text -

Understood Tom. Wheeler looks at the subject from many angles but
does
not get into overall specifics. For instance, the smallest volume
antenna can be based on wire size which in turn is based on power
output.
This effectively states that the smallest radiater is the size of a
pinhead!
Practicality states that the wire diameter is exceedingly small
diameter
plus extremely low power, all of which is based on a arrangement that
is
resonant. In practical terms I would point to a Fractal antenna
however, the
criteria for 'smallness' or 'compact' must factor in efficiency with
respect
to wave length where the latter antenna would fail. Same goes for the
EH
antenna which only can be regarded as a 'system'. Or for that matter
a
resister which as a load is just a heat exchanger.
In the amateur field one should incorporate max power allowed on key
down for a certain period of time without loading of any sort and
where
radiation is rated with respect to a unit volume. With that in mind I
have found nothing to aim for to qualify as a 'small' or 'compact'
antenna.
Looking at the trade magazine 'Antenna' there is always demands for a
"smaller"
design antenna as something that is holding up electronic progress,
but at
the same time zero reference as to what defines 'small' since design
is
covered by Maxwell and not by Congress
Best regards
Art Unwin.