DIY Fractal Antenna

[Tomterrific]

I bought a cheap 19" TV and needed an antenna. I ran into this design and found it cool enough to build.

T

[WizardOfOdds]

Very interesting. How well did it work (relative to any other antenna you tried)?
It's hard to judge the size from your photo, how big is it?
I know some ham claims to have shown that ONLY a fractal antenna has some unique bandwidth properties, but what are you observations?? Do you have a reference link?? I might try building one too. What material did you use? What impedance do you match to (balun??) and transmission line?

Thanks for the post.

[Kenp51]

I have seen those videos. Work good if you are not to far away from the tower. how far is to far, don't know.
Correct me if I am wrong but fractal antenna are common in cell phones, I think
I live 50+ miles from the towers we see at home. The right weather conditions might work for the stronger UHF channels.

I have built 3 bow tie antennas now. 2 were 4 bay units with a reflector (hard ware cloth) 9" bow ties. First one was just a thrown together test unit leaned against the house (I literally used some baily wire). Worked OK most of the time. Second was the same design, but better construction and materials (aluminum elements) mounted about 25', but also incorporated a VHF loop antenna. Worked some what better. High 70% signal strength
Heavy big sucker. No chance you would want to haul them around.

My latest is a 6 bay. 4 7" bow ties pairs and 2 11" pairs. All I can say is HOLY COW, WOW. 97% to a low of 95% in poor conditions.
http://imageevent.com/holl_ands/multibay/uhfvertical6baybowtienorefl
I incorporated 2 folded dipoles with reflectors on top for VHF. Mmmmmm so, so. Better than the loop, but does drop out in poor conditions. Will just go with a ready made solution.
http://www.mcmelectronics.com/product/STELLAR-LABS-30-2476-/30-2476

The VHF 6 bay bow tie is supposedly scalable. Meaning it should scale down to Wi Fi range. No reports of any doing so.
Fact is I am not to sure how many if any people have built the 6 bay. I was requested by the fellow that did the optimization software sim to post multiple pictures of mine during build and up in the air.

Man it is a big sucker. Weighs a ton. Was a real son of a gun to erect. Heavy! YOU AINT TAKE THAT SUKER ON THE ROAD, BELIEVE ME!

But man does it work good. Well except for the VHF. I will replace the folded dipoles with a single unit that I linked above.

Not to shabby for steel wire (2 wires twisted together to form elements). I have enough rescued aluminum to build another.

The 6 pair could be built on a sheet of foam board, thin ply, or coroplast by using copper tape that is used by stained glass hobbyist (solder all interconnections). With a little planning you could make it foldable, and then just unfold for use. You would need to incorporate some stiffeners for unfolded. Would not have a reflector. But if your clever you could come up with something. Pretty much an indoor solution unless you used a weather proof material to put the elements on (coroplast?)

Her is my unit mounted to the side of the house at about 15'. I really was afraid to go high because of the wight and sail loading, although it just took 50+ mile an hour winds no sweat.




Ken

[Tomterrific]

The design was found on line and printed out. The elements are HD aluminum foil glued to the printed paper and cut out. Then I used two sheets of clear laminating plastic to contain the fragile foil elements. The balun is a 75 ohm, I think. It is attached to the foil through two holes punched into the laminating plastic. It works but I don't know if it is better than a random tangle of wire.

After I built this I thought about a dedicated trailer antenna right on the side of the camper wall. Thin wire or that copper foil used for window alarms. A nice 8 gang bow tie should fit on 4 feet.

T

[Kenp51]

Yes the old antennas will work just fine. Digital, analog, the antenna don't know or care.
The difference being is that the antennas designed for digital hd are tuned for a more narrow band. The UHF channels above 51 no longer exist as real channels that are broadcast. Above channel 51 are actually virtual channels. And in the VHF band the lower channels (I think below 9 are also virtual). Many tv markets do not even have any broadcasters in the VHF band. Were I am there are just 2 (on real channels 9 & 10, even though the use their old virtual numbers to Identify themselves). Confused yet?
So the old antennas being tuned for wider bands are not as sensitive on the real channels being broadcast now. But yes will work just fine.
The old VHF band went from channel 2 (?) thru 13. and the old UHF went up above channel 70 at one time. So by making the antennas tune a more narrow range they are actually more sensitive in the presently defined bands. The 6 bay bow tie I am now useing would work like crap on the old UHF band above about channel 46. It actually peaks on channel 26 (falls off sharply below 26) with a slight drop (1/2 db) to 46 then falls off sharply again.
If you have one of the old antennas that is still in one piece. It will actually work just fine. Especially if you are not real far out. Many of the old units were designed for deep fringe and although not as sensitive on the current bands will still give a very pleasing results.

Antennas are not by any means a hobby of mine. I am just to cheap to pay a hundred plus bucks for a UHF antenna, when I was able to build a better performing antenna for about $25. Ended up learning way more than I wanted to.

Ken

[Kenp51]

The design was found on line and printed out. The elements are HD aluminum foil glued to the printed paper and cut out. Then I used two sheets of laminating paper to contain the fragile foil elements. The balun is a 75 ohm, I think. It is attached to the foil through two holes punched into the laminating plastic. It works but I don't know if it is better than a random tangle of wire.

After I built this I thought about a dedicated trailer antenna right on the side of the camper wall. Thin wire or that copper foil used for window alarms. A nice 8 gang bow tie should fit.

T

Sounds like a plan "Stan"
I want to see what you turn out. And get a test report.

I got to thinking it would be cool to use a rollable substrate (cloth. flexible thin plastic?) and glue flat elements to it. You could unroll it and use a pvc frame to hold it in. Should work good as long as you do not need to sit it up very high.

Ken