FlightAware Discussions

Three Easy DIY Antennas for Beginners

[quote=“PeterHR”]

For cutting the aluminum drink can (Pepsi/Coke/Beer), I have used:

  • Scissors as described by Peter.

  • Stanley knife.

The can wall being very thin, it was easy to cut it using scissors or knife.
Cutting a food cans made of iron sheet is a bit tough & requires tin-snips.

The sharp cut edge can easily injure fingers during cutting & subsequent handling. A layer of tape should be applied around the cut rim of food/drink can.

An example of cutting the tin: “the cutting edge technology” :smiley: :wink:

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I have tried all these designs, and more. Even did a stripline antenna out of printed circuit board, which simulated a coaxial collinear design. This has been the best one so far, best range. Almost double any other one I have tried. Note, I use BNC connectors instead of N:
http://www.topsecretbases.com/images/coaxial.colinear.jpg

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A vast majority of those who make a DIY Coaxial Collinear antenna (CoCo), get disappointing results, and relatively few lucky ones get good results. For this reason I dont recomend it for beginners, and that is why I did not include it in this thread which specifically says “Easy Antennas for Beginners”.

Once the beginners get their system established with easy and reliable 1/4 wave whip with various types of ground planes given in this thread, they can venture with tricky antennas like CoCo, Franklin, Coiled Whip etc.

Anyway thanks for posting the drawing of the CoCo. Looks a nice design. Interested members can give it a try.

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Related: FlightAware ADS-B Filters Now For Sale In US

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I’ve actually had pretty good success with the fixed antenna that came with my Nooelec RTL-SDR once I trimmed and then magnetically attached it to a piece of metal bar stock. I’ve since built a cantenna which is working well, but today while I was cleaning up my workbench I disassembled the little antenna that came with the RTL-SDR and in the process I think I may have stumbled across what may be the easiest beginner antenna possible, which should give great results with very minimal effort. The antenna that came with my RTL-SDR is below.
https://googledrive.com/host/0B4OdERgi_-jAVzZQN3o1dkdwY00/IMG_2237.JPG
Here is the exploded view of the parts:
https://googledrive.com/host/0B4OdERgi_-jAVzZQN3o1dkdwY00/IMG_2239.JPG
Now, the only tricky part about just cutting this element to size, is that you have no idea where the coax is separated inside the unit without disassembly. I’ve measured mine, and it looks like 15mm would be the appropriate amount to deduct from the element length to obtain that magical 68-69mm element length. If you have a similar antenna, it doesn’t look like the manufacturer could vary more than a few mm from this unit to unit.

So,

Step 1: Unscrew the element from the base, remove the rubber tip and then measure 53mm (68-15, because 15mm of the effective element is inside the antenna base), measure the 53mm again (knurled part of the antenna included (you always measure twice :smiley: )) and then cut it with a heavy side cutter or hacksaw. Replace the rubber tip.

Now the problem for step 2 is what to do with that tiny included ground plane… Mine was attached with just a small dab of glue, and it appears to be mostly press fit into the plastic base. I think if you were more gingerly in your approach than my “side cutter brute force technique”, and just worked a guitar pick or small precision screwdriver around the base you could separate it easily. Once your inside, this is what you’ll see:
https://googledrive.com/host/0B4OdERgi_-jAVzZQN3o1dkdwY00/IMG_2234.JPG
Not very impressive, they just wedged the loose ends of the coax ground in between the lip of the base and their tiny ground plane.

So,

Step 2: Remove the ground plane and make sure no loose strands of copper are contacting the center coax.

Now, Step 3 is a little more open ended, but essentially we would take this trimmed unit and attach it to a proper ground plane. After some thought, I think the best method would be:

Step 3: Discard the ground plane cover sticker and then drill a small hole in the center of the ground plane, a matching hole in a small bean/soda/etc can (preferably trimmed to 68mm in height), and then screw or bolt the two togather. You could also just skip drilling all together and solder or weld the ground plane and can together (conductive JB weld might be a great solution for this). When your done you should have something that looks and functions like the popular “cantenna” design, only with the coax coming out of the original antenna base and not the bottom of the can.

Also, since the ground plane has a small magnet hastily stuck on it you could just try magnetically attaching it to various ground planes to experiment with what works best. Just make sure you get good electrical contact between the two pieces of metal (great use for your multimeter! :slight_smile: ). With a little ingenuity you could also fabricate a 68mm/68mm 90 degree dual purpose mounting bracket/ground plane from of a piece of flat steel for a very clean looking antenna.

Happy antenna modding! - KB9OVP

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I 100% agree with abcd567 comments.

Don’t run until you can walk :smiley:

Build a dipole or 1/4 wave ground plane antenna first, then you have a reference to test other more complicated designs against.

In many cases problems associated with slight differences in material, dimensions and construction techniques, reduce the effectiveness of such designs. These frequently turn out to be less efficient than easier to build, and more tolerant designs such as the 1/4 wave ground plane.

The Coax Collinear shown earlier in this thread is a good example of a design that frequently appears in different guises on the internet, but is not likely to work at all well.

If you put a lot of effort into building a complex antenna, surely it’s worthwhile taking an extra bit of time to test it against a known reference, in order check that it is performing as it should do ?

Sadly very few people seem to do this before posting on the internet, so flawed information continues to propagate.

Regards,

Martin - G8JNJ

www.g8jnj.net
www.tc2m.info
websdr.suws.org.uk/

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Trimming down the antenna element to something like 1/4 wave long at 1090MHz will make a big improvement to the performance of the stock antenna.

Unfortunately there is a lot of variation in the quality of the mini mag mount antennas supplied with RTL dongles. The main problem is the very thin coax cable, which sometimes has a very poor outer screen (just a few strands of cable which are not woven around the inner core) or badly soldered end connector with long ‘pig tail’ wires hidden inside the plastic moulding.

I have found that some of these short lengths of cable had greater than 10dB loss at 1090MHz, so even a paper-clip connected directly to the dongle would provide better results. :cry:

I’m not saying that they are always bad, but the vast majority of the ones I’ve seen have been.

Regards,

Martin - G8JNJ

www.g8jnj.net
www.tc2m.info
websdr.suws.org.uk/

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No doubt the supplied cable isn’t very good quality, and even more concerning to me is the possibility that some shield strands are contacting the center inside the mini antenna base. I still received pretty darn good results (over 240nm returns) with the trimmed minimag and just a piece of ungrounded bar stock. For a free antenna that only requires about 10 minutes of work and no additional parts I think it’s not a bad option for someone to at least try out as one of their first tests. Expectations need to be tapered however, becasue as previously mentioned, one doesn’t necessarily know what their minimag is built from (other than 25c worth of parts :smiley: ).

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The Coax Collinear shown earlier in this thread is a good example of a design that frequently appears in different guises on the internet, but is not likely to work at all well.

How true :confused:

Some great information on the links in your sig. Many thanks Martin.

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Hi Martin!
Nice to see that you finally made it to Flightaware forum.

Please see this thread started by me on August 25 (credited to you).

DVB-T RTL 820 as 1090 Mhz Signal Generator

Regards,
ab cd

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Hello! Thank you a ton for the guide. I was just recently introduced to ADSB tracking and I saw this post and was instantly intrigued. I live in a remote town (from aviation) and live in a terrible apartment building without access to the roof, so my location is not ideal… However after building a cantenna for very little cost I already notice a huge difference!

I would love to know more information about exactly how this works… I understand wavelength = c/freq, but maybe making a guide about why the diameter of the can, the length of the can, and the length of the whip all make a difference and what roles they play.

Even if that doesn’t happen just wanted to give my thanks! Seeeyaaa!

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I used this 4 leg version and encased it inside a piece of 4" PVC with PVC caps on the end. Only the center whip protrudes through the top cap. It works far better than the 11 segment coaxial antenna. I’m constantly seeing aircraft at the 300+ mile range with this little antenna.
The whole project fits inside of the PVC tube abt 8" long. The Nooelec plugs directly into the Pi. I used a cigar lighter adaptor to USB for power. I soldered red/black rip lamp cord to the cigar lighter and ran it down into the garage. I made some standoffs and mounted it on my tower about 20’ high. It hits my network via the USB wifi dongle.
I power it with a 12v 35ah battery that I have to charge every other day. It appears to draw around 375 ma once it is booted and running for a few minutes.
It’s been very reliable.

Don

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Hi,

Looking around my shed I’ve everything I need for a cantenna apart from a mcx-sma connector, which is on order.

I’ve even found an mast clamp and some plastic tubing. Now the $64K question. Can I mount it above the TV antenna or should I keep them separate and fit another wall mount?

Thanks

Phill

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Generally more than one antenna can be mounted on same mast if there is sufficient clearance between them.
If you post the photo of your TV antenna, it will help to answer.

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Thanks for the reply abcd567!

Here is the TV antenna.

I’d forgotten there was a wimax antenna on it too. There is sufficient pole to raise it about another foot. To be honest it’s probably no more hassle to put another mast at the other side of the roof if it’s likely to be any problem.

Here is my minimag on a paint tin.

And the coverage I get. It matches well with the plot given by “HeyWhatsThat”

BTW the tin is on the windowsill. Picture is inside looking out.

Many thanks

Phill

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@phillx19090:
Raising existing pipe (which currently holds 2 tv antennas) by another foot and installing adsb antenna at top will be ok. However you have mentioned that it is same hastle to raise existing pipe or install a new pipe. In this case, I will prefer to install another pipe for ADSB antenna, rather than raising the existing pipe by another foot.

A separate pipe for ADSB antenna on other side of your house will give advantage of having enough space for adding second adsb antenna, or replace smaller antenna by a larger antenna, and no disturbance to tv antennas while working on adsb antenna.

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Hi abcd567,

Thanks for the advice, it’s greatly appreciated.

I’ve salvaged 5 feet of 2 inch steel tube, some steel bar to make some clamps, and a metre of plastic tube to mount the cantenna on. The only problem now is to somehow persuade my wife that I’m working on the roof and not actually putting an antenna up. 8)

Once that is done I’ll see how it goes. Since I have high ground north and south of me it may be that using other devices on the cable may not show much improvement. I do have a good gap out towards Ibiza and Mallorca which might benefit.

One step at a time.

Kind regards

Phill

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Don’t worry, this is a universal problem. My wife thinks I have spoiled the beauty of our home by my “ugly” antennas, cables, and other equipment. She also thinks that I am wasting my money, time & energy on a useless and crazy hobby. :smiley:

Amplifier will sure help.

Outdoor installation of Cantenna may result in:
(1) The whip may be blown away by strong winds.
(2) Moisture/rain water may enter the connector and coax.
To prevent both the above problems, apply few drops of hot-melt glue or silicone sealant around the F-connector at the point where whip inserts into the connector. See an example of Silicone applied at F-connector/bottom of whip in photo below. You can apply some more Silicone sealant or hot-melt glue around the nut of connector to prevent rain water/moister going down to coaxial cable inside the can.

Example of Silicone sealant/adhesive applied at F-connector (made by member jepolch)

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:smiling_imp:

She dare not go as far as UGLY! Else I might have to do something about the 2.8m dish in the garden. She is more likely to complain about the “hair cut” I’ll be giving one of the trees that’s just in the wrong place.

Thanks for the advice about using silicon sealer. I’ll do that and look at getting an amp sorted out.

Many thanks
Phill

That wire pocking out of the can is resourceful but probably only suitable for indoor use or the attic. It is a nice idea though but to make it outdoors compatible, you would have to probably pot the inside of the can and cover it with a few layers of lacquer. There are better ways to make an outdoor antenna that would last much longer, with less effort and work better.

With an outdoor antenna you want something structurally sound, not some thin wire waving around waiting for some bird to take an interest in it :slight_smile: Think thicker as in copper tubing, not wires. BTW there is no advantage in using solid conductors for the antenna elements as most of the energy is very close to the surface of the conductor. You really don’t even need solid copper tubing to make a good antenna since only the surface and a very small depth into the conductor carries 99 percent of the energy. Steel tubing works almost as well and much cheaper.

PS there is an unfilled market on Ebay for anyone who knows how to do that right at a reasonable price :slight_smile: