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Author Topic: Ultra-light VHF Yagi: 3 oz!  (Read 2833 times)

IZ2UUF

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Ultra-light VHF Yagi: 3 oz!
« on: September 10, 2013, 11:40:15 AM »
Hi dear friends.

Speaking of light antennae, I built a 4-elements VHF Yagi for portable use. It weights exactly 83g (<3 oz).
Once disassebled, it is strong enough to withstand transportation strapped to the outside of one's backpack.
This is the project with the building instructions:

100g Yagi

At this link there is another build of this antenna by Matt K0MOS, who is a very active SOTA activator in the U.S. He compares this antenna with his previous portable attempts.

I hope it could be of your interest.

Davide
« Last Edit: September 10, 2013, 11:42:34 AM by IZ2UUF »

KC3AOL

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Re: Ultra-light VHF Yagi: 3 oz!
« Reply #1 on: September 10, 2013, 12:17:56 PM »
Very nice, but I wonder how much that fishing pole section would cost?

Another idea...something that my ham radio club did (which they got the idea/plans online) was to use measuring tape for the elements.  I'm not sure how much they weigh compared to the welding rods (probably more), but they are pretty light and coil up tightly when not used.  The main beam was PVC though and that makes the whole thing a bit heavy.

One of these days, I might have to work on my own design using the measuring tape, some carbon fiber arrows, and some 3D printed parts to hold it all together.

Edit: I just looked and fishing rods (without reel) are a lot cheaper than I expected.  I quickly found a 16 foot rod that is in 5 sections for only $24.  That's probably cheaper than my idea of using arrow shafts.
« Last Edit: September 10, 2013, 12:28:27 PM by KC3AOL »

IZ2UUF

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Re: Ultra-light VHF Yagi: 3 oz!
« Reply #2 on: September 10, 2013, 12:37:41 PM »
Very nice, but I wonder how much that fishing pole section would cost?

Another idea...something that my ham radio club did (which they got the idea/plans online) was to use measuring tape for the elements.  I'm not sure how much they weigh compared to the welding rods (probably more), but they are pretty light and coil up tightly when not used.  The main beam was PVC though and that makes the whole thing a bit heavy.

One of these days, I might have to work on my own design using the measuring tape, some carbon fiber arrows, and some 3D printed parts to hold it all together.

Edit: I just looked and fishing rods (without reel) are a lot cheaper than I expected.  I quickly found a 16 foot rod that is in 5 sections for only $24.  That's probably cheaper than my idea of using arrow shafts.

If you look at Matt's blog, he worked a lot both with measuring tape and fiber arrows made antennae. He explains why he decided to discard them to go for my design.
Measuring tape antennae are heavy and fatiguing if you hold it with your hands; also, measuring tape keeps bending over under moderate wind.
Regarding fishing poles, we need fiber-glass one (not conductive carbon fiber). Fiberglass rods are cheap stuff for very entry level fishermen. In Europe there is a chain of sport shops called "Decathlon" that sells a 3m, three sections long fiberglass rod for 5 (7$ more or less). I don't fish and I have no idea what is for, but it seems designed exactly to make this antenna.

Davide

KC3AOL

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Re: Ultra-light VHF Yagi: 3 oz!
« Reply #3 on: September 10, 2013, 12:55:24 PM »
Ok, I didn't look at the blog.

Good points about the tape.  They do tend to bend over if you wanted to change the orientation of the antenna.

I also hadn't considered that carbon fiber would be conductive.  I'm guessing that they wouldn't be conductive enough to use as elements?

IZ2UUF

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Re: Ultra-light VHF Yagi: 3 oz!
« Reply #4 on: September 10, 2013, 12:59:14 PM »
I also hadn't considered that carbon fiber would be conductive.  I'm guessing that they wouldn't be conductive enough to use as elements?

No, unfortunately carbon fiber is conductive enough to disturb but not to make a reasonably efficient antenna. It is more a resistor than a conductor.

Davide

Radio Preppers

Re: Ultra-light VHF Yagi: 3 oz!
« Reply #4 on: September 10, 2013, 12:59:14 PM »