A whole other kind of antenna to be kept in mind along with plasma antennas and ambient energy antennas
http://en.wikipedia.org/wiki/Fractal_antenna
A whole other kind of antenna to be kept in mind along with plasma antennas and ambient energy antennas
http://en.wikipedia.org/wiki/Fractal_antenna
With a very tiny antenna how would the "10-foot rule" apply?
Field Strength rules would apply .... would be my guess. I think FCC leaves doors open to use whichever rule it chooses to apply. They know tinkerers come up with weird antenna systems ... always have, eh 😉
Cool idea though. I would think that with as low power as we are using, it might need tuning somehow .. maybe not as critical as in more emphasis on one portion than another, but still needed to get the most out of 100mw. Easier to load too, it would seem.
Fractal antennas, from what I can read, is the combination of inductance and capacitance produced by computer generated geometric shapes and paths to produce resonance at several frequencies simultaneously. This means the theory used in the operation of fractal antennas is nearly the same as "Isotron" antennas in use in ham radio Part 15 stations for years. It would appear fractal antenna applications are mostly used for microwave and above frequencies. I have yet to find any radiation efficiency studies for BCB frequencies except digital and HDTV applications.
Nathan Cohen is the modern father of fractal antennas, and you're right, it looks like most of his studies, and Fractal Antenna Systems, Inc., have a lock on much of the microwave market. But as a Ham, he started with a 2-meter fractal antenna because at his apartment they wouldn't let him have a 'normal' antenna. He's quoted as saying he talked with people across the Atlantic with only 1 watt.
Meta-materials notwithstanding (incorporating antennas into clothing to monitor vital signs), the main material is still copper.
I've been trying to run some numbers based on interpolation of existing graphs and patterns. The main problem at midband freqs is that with, say, a Koch tree, you need so many iterations that it's very difficult to construct one beyond third order without branches crossing.
So, you'd think the key would be starting with a larger size. The problem is, using wire, by the time you get enough iterations to make resonance at midband freqs, you have too much mass.
Perhaps if we could create a very large PCB and reflector, it might work. But, like you, even though I've spent about 20-odd hours of late night research over the past week or so, Every indication is that the experts are still investigating if fractal antennas can be used at lower bands.
So, I'm back to looking at the work these Russians did:
These are different than models based upon Koch trees, Minkowski islands, etc. If larger scales and more iterations don't work, they'll make very nice garden decorations 😉
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Heard anything recent or new about the application of fractal antennas to MW transmission? Or, for that matter, FM transmission.
We need projects to build our own experimental fractal antennas.
Bring your ideas to submit at the next ALPB Meeting.
My only experience has been with 2.4 GHz equipment and I have yet to observe a fractal antenna which will perform as well as a dipole. They may exist but not in my experience.
Common antennas used in this band include the PC loop, the coil antenna,and the wire whip but these do not compare well with the dipole. They are usually used for space savings. The limits for the ISM band are based on field strength and it is common for designers to use a small antenna and make up for the gain disadvantage by increasing the power. This is similar to what we do for FM BCB.
Unfortunately, for AM Part 15 both the power and antenna gain (the 3 meter rule) are restricted. If an antenna using fractal geometry which increases the radiation resistance can be designed within the 3 meter rule this would be an advance in our technology.
Upon reading that fractal reception antennas are part of modern automobiles for AM/FM radios, my thought did a 180-flip and anticipated what Neil just expressed:
Neil: "If an antenna using fractal geometry which increases the radiation resistance can be designed within the 3 meter rule this would be an advance in our technology."
As savory as that would be, don't we suppose the FCC would manipulate the rules accordingly and set us back 100 years?