Self-built aluminum-tube-dipole (With pictures)

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JEL
Posts: 83
Joined: Wed Feb 07, 2018 2:08 am

Self-built aluminum-tube-dipole (With pictures)

Post by JEL » Tue Feb 20, 2018 4:26 am

I have built an aluminum-tube-dipole antenna and are running tests on it now (For a couple of days now) to see if it has benefits or drawbacks over a thin wire-antenna.

My primary focus is aviation, so that's the frequency-band for this experiment.

I was browsing around a local store, that sells tools and parts for homes and cars and all kinds of other things too, last week. I didn't have any set goals for what to get, except that it had to be something that could be used in antenna-experiments.

In the car-part section I noticed some aluminum tubes.
Now, I'm not a car-guy, but they were in the cooling-section, so I assume they're for air-conditioning systems or something like that.

Anyway, they looked suitable for an experiment :)

They are stretchable, like an accordion or pair of bellows. I believe they are technically called 'concertinaed' tubes (I'm not native to english language, so not completely sure about that word)

They are only conductive on the inside, for some reason, and are coated with some type of slightly sticky resin on the outside.

The material itself is very thin, but the diameter of the tubes is 60 mm (~2.36 inches)

They were 500 mm (~19.7 inches) originally, which I stretched to (As close as I could get) 600 mm (~23.6 inches) (Really only a slight stretch, so nothing that really changed their composition much. They still have their 'accordion' grooves)

I mounted them with a gap of 30 mm (~1.18 inches) onto a painted (So it's non-conductive) metal garden-tool-mount (A thing that goes on a garden-shed wall to hang garden-tools on)

I soldered (Aluminum is not soldering-friendly, but thanks to the grooves I got it to work) two thin wire-pieces to the inside-ends of each tube, and led them out (Perpendicular to the tubes) to a small TV-aerial-plug connector I taped to the side (This is as self-built as it gets :) )

I then hung the entire contraption onto a metallic horizontal bar which is 2 m (6.56 feet) above the floor near a window (It's the same bar I use to provide ground for the monopole antennas I have hanging upside-down from it)


Ok... plugging it in... pressing play on SDR#...


First impression:

I had to lower the gain a bit. Apparently there is a lot of signal coming in through this thing.

I have a national FM-radio tower 3.4 km (2.11 miles) from my position, and it hit above zero dB with the gain-setting I normally use. I would say the gain appears to be about 3 dB above the thin monopole and dipole wire-antennas I have experimented with so far (Although I'm not sure if it's actual gain, or perhaps rather some effect of possible wider band-width that causes a boost in the overall signal-peak)

The air-band stations also appear a tad stronger though.
The airport tower is 70 km (43 miles) from my position and is normally hard to hear with the monopole and dipole wires (Although not impossible. Some days are better than others), but I can just get it with the tube-dipole (At least for the time being. But I guess, over the coming weeks/months I will, probably, find out if it's due to weather or if the antenna is really consistently better than the wire antennas)

Finally a few pictures of the thing :)

I have to say, as a geek, I think it looks pretty cool, if I may say so myself :)
Also; you can see the thin wire-dipole hanging right next to it. It has the same length, but is obviously much thinner (It's hard to see, but the TV-aerial-plug is visible on the lower right of the image)

I don't know if this tube-design has any adverse effects, somebody with more experience/knowledge may know, but I'm liking it so far)

DSC_0556_Final.jpg
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Username
Posts: 293
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Re: Self-built aluminum-tube-dipole (With pictures)

Post by Username » Sat Apr 14, 2018 1:36 pm

:D SDR# Pictures?
Where are you from?

rtlsdrblog
Site Admin
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Joined: Mon Nov 19, 2012 11:54 pm

Re: Self-built aluminum-tube-dipole (With pictures)

Post by rtlsdrblog » Sun Apr 15, 2018 11:15 am

Nice idea. Generally when you increase the element diameter the range of resonant frequencies increases. So now you can receive more frequencies on the same antenna.

JEL
Posts: 83
Joined: Wed Feb 07, 2018 2:08 am

Re: Self-built aluminum-tube-dipole (With pictures)

Post by JEL » Sun Apr 15, 2018 3:46 pm

Username wrote:
Sat Apr 14, 2018 1:36 pm
:D SDR# Pictures?
Where are you from?
SDR# Pictures ?

Current QTH is cold and rainy Denmark.

rtlsdrblog wrote:
Sun Apr 15, 2018 11:15 am
Nice idea. Generally when you increase the element diameter the range of resonant frequencies increases. So now you can receive more frequencies on the same antenna.
It's tuned for the air-band, but picks up, with fair signal-strength, from 11-meter band to 2-m band.

illllm
Posts: 16
Joined: Tue Apr 17, 2018 5:41 pm

Re: Self-built aluminum-tube-dipole (With pictures)

Post by illllm » Sun Apr 22, 2018 1:20 am

"Generally when you increase the element diameter the range of resonant frequencies increases"

I'm thinking Two large aluminium turkey fryers make better antenna :P :o :mrgreen:

sorry...just kidding :mrgreen:

JEL
Posts: 83
Joined: Wed Feb 07, 2018 2:08 am

Re: Self-built aluminum-tube-dipole (With pictures)

Post by JEL » Sun Apr 22, 2018 7:06 am

illllm wrote:
Sun Apr 22, 2018 1:20 am
"Generally when you increase the element diameter the range of resonant frequencies increases"

I'm thinking Two large aluminium turkey fryers make better antenna :P :o :mrgreen:

sorry...just kidding :mrgreen:
Haha, funny you should mention it, I actually bought a pack of cheap barbecue grease trays to experiment with :)

Not sure the tray makes much difference though, because I got about similar reception on a loop-antenna tuned to the same frequency as this 'tray-tenna' :)

But at least I didn't have to do any soldering on this one :)
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DSC_0569_Final.jpg
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Username
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Re: Self-built aluminum-tube-dipole (With pictures)

Post by Username » Sun Apr 22, 2018 8:48 am

How did you tune them and for which freq?!
Is the size of the Alu Pan matter or does some cm more or less not that important?

JEL
Posts: 83
Joined: Wed Feb 07, 2018 2:08 am

Re: Self-built aluminum-tube-dipole (With pictures)

Post by JEL » Mon Apr 23, 2018 7:18 am

The 'tray-tenna' is tuned to the frequency's half-wave (The brown wire sticking straight up)

The tray is just left as it is. I haven't tried different sizes.

I'm guessing the tray works like the roof of a car.
I don't know if the vertical length (The 4 sides of the tray) has much effect, if any.

The loop-antenna I tried, which was a full wave-length of the same frequency, was just as efficient as the 'tray-tenna'.

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