Thread: I bought some aluminium tube to make antennas

Concerning the antenna aspects of this thread only ...

If I were making something like this, I would ...

Use 20x20 mm RHS aluminium as the boom, redesigning the element lengths for conductive boom.
(Removes the need to drill the boom accurately for the elements).
Use 20x6 mm flat aluminium for the elements, other than the driven.
But you have already bought the tubing, so...
Screw (304/316 SS) or rivet (AL+AL) the elements to the boom.
No need to worry about the "electrical" connection of elements (other than the driven) to the boom; it has no effect whether they touch electrically or not, for this design.
Use a balun (a number of smallish loops of coax cable in a coil) as per original design, but must be in low loss coaxial cable.
Use low loss 75 ohm TV type foam cored coax cable for balun and feeder. (Do not use RG58 or ordinary RG59).
No need for 16 million shields on the cable, one will do, but most cables of this type are now quad.
Use coax adaptors to mate with modem or phone.

The lengths of the front directors seem a smidgen short, and 1/2 wave at approx 1200 Mhz?
May be correct, as the driven is about right.
You will probably achieve the required bandwidth anyway at this frequency, due to "construction constraints" (unintentional dimensional and construction compromises) and the diameters of the directors and boom.

Just suggestions.

Good luck, and let us know how you get on please.

cheerio, mike

If I were making something like this I'd go on ebay and buy a yagi antenna kit for about $30...

Originally Posted by mike48

Concerning the antenna aspects of this thread only ...

If I were making something like this, I would ...

...

Just suggestions.

Good luck, and let us know how you get on please.

cheerio, mike

Hi Mike,

Thanks for your interest in my project.

I actually want to make a few different antennas from here: http://whirlpool.net.au/wiki/homemad...emade_yagi_pg2 (where the earlier link to the antenna came from)

While there is a certain attraction to a 16.5db antenna, there is another attraction in an 11db antenna that is only 1/5th as long; much easier to put up the mast and then you can pick the smallest antenna that will do the job.

I am experimenting with a construction method that will allow strength and rigidity without too much weight and can flatpack in the back of the ute in spaces that can't generally be used as useful cargo space.

Between now and Easter I will be working on these ideas with 850mhz NextG as well as 1800mhz LTE antennas.

The antennas themselves are cheap as chips. For my $15 worth of aluminium I can make every antenna I could possibly want. Allowing for the cost of the boom and some coax connectors I can make one of the smaller antennas for about $7 and the biggest ones I want to make for about $15.00. That's why I wouldn't even consider a $30.00 yagi kit on ebay. Most of the cost of the project is actually the patch leads to the phone and the wireless internet device and the coaxial cable, which I doubt would be in the ebay kits. All the antennas can share the same coax and patch lead in the experimental stage.

Yes, I will post some results, but I am not one to document every hole drilled or cut made.

I will probably post some photos of finished antennas and a bit of a write-up of construction/design details and how they perform.

Just dont expect it tomorrow, or the next day

Cheers

Doug

Some come with leads some don't.

Here for those that don't have the ability to make their own.

G'day Doug

I really doubt that you will find any high gain 900MHz band yagis on eBay for less than $100 or so.

Yes, connectors etc form a large part of the constructor's cost.

That Whirlpool website is always worth a look on many of these subjects.

mike

Originally Posted by q9

Some come with leads some don't.

Here for those that don't have the ability to make their own.

Hi q9,

thanks for the link.

Those antennas on the link look quite good and reasonable for the price, but they are not suitable for my purposes.

The frequencies they are tuned to are not the ones I am targeting. For my camping trip at Easter there is no point in looking at any other frequency but 850mhz Next-G. The higher frequencies just wont have the range to get to where I am going no matter how big the antenna.

The 16db gain antennas in your link are for 2.4 ghz, a much higher frequency and therefore can be a lot smaller for the same gain. The ones in the link are less than half a metre long whereas the one for 850 mhz is just under 2 metres long. Even the Chinese wont make you one like that for $30.

The higher the frequency the higher the data rate but the shorter the range. The lower the frequency the slower the data rate but the longer the range (as a general rule, all else being equal)

I did mention making some 1800 mhz LTE ones too but they wont be any good where we are going. There is no 1800 mhz tower anywhere near where we are going this time but they may be useful in other destinations, for example camping close to a larger rural centre that has 4G coverage.

Cheers

Doug

So, Doug, how much did you make over the weekend?

We did expect a report you know - like from the site itself - realtime and all that.....

Just a guess, given the absence of any report: it didn't work.

Originally Posted by FenceFurniture

Just a guess, given the absence of any report: it didn't work.

Thanks for the reminder Brett.

The antennas do work but I was not able to get a signal where we were camping.

I did trial them in areas of low signal before we went and they did very successfully boost the signal.

Once we left the camping area yesterday I drove past the site of the phone towers and they are very close to the ground, seemingly only there with the intention to serve the township and not much of the surrounding area.

The antennas will still be good for other places and there may be a couple of things I can try differently next time I go back to where we were for Easter.

It was still a worthwhile experiment. If nothing else it was an exercise in getting precision results on a drill press.

Cheers

Doug

Originally Posted by doug3030

If nothing else it was an exercise in getting precision results on a drill press.

It's worth waaaay more than that - finding Tube with an ID is, as you said before, "PRICELESS".