FlightAware Discussions

Which one is the best antenna?

Which one is the best antenna?

If there was just one “best” antenna, everybody would use it. The best antenna for one particular situation may not work well somewhere else. There are three rules of antenna installation:
• Any antenna is better than no antenna.
• Bigger and higher are generally better. If small antennas really did work as well as big antennas, nobody would spend the time, money and effort to put up the big ones.
• Every antenna installation is a compromise.

There are several factors that must be considered when engineering an antenna installation. Height? Size? Weight? Restrictions? Cost?

Now there is a factor that we all have to compromise on with every antenna, cost. Should I build it or buy it? Many antennas can be scratch built for a fraction of what they cost readymade, but are they bargains? Mostly antennas are advertised for $75 to $150 but the same performance can be had from a home built antenna costing less than twenty dollars. A vertical antenna can be constructed from a 1 to 2 meter piece of coax (coaxial collinear) or electrical copper wire, or aluminium, brass, or copper tube (1/4 wavelength groundplane, wire collinear with coils & franklin collinear with hairpin stubs) for a few bucks. However they may be difficult to design and tune (except the naturally tuned 1/4 wavelength groundplane) if the Amateur doesn’t have a background in engineering or key pieces of test equipment. The truth is, when you buy a ready-made antenna, you aren’t just buying a collection of coax, wires, tubing, and connectors, you are also purchasing design expertise.

Do you get your money’s worth? Is the kit of parts complete? Is the hardware stainless steel, or are you going to have to deal with a corroded mess after a couple of years? Are the directions clear, and detailed? Some antenna manufacturers provide a single sheet with a quick sketch whereas others provide a manual running to several pages. Usually the bulk of even a complex antenna is fairly straightforward in assembly, with a single part requiring tuning. When you get to the tuning, either (1) the manufacturer has designed the assembly so it could be tuned at the factory; or (2) he has provided detailed instructions on how to accomplish the procedure; or (3) the instructions are vague and misleading; or (4) you are left on your own. The author has experienced all of these conditions.

The quality of the instruction manual is of primary importance when selecting a ready-made antenna. Some engineer built a number of prototypes to come up with the design the manufacturer decided to market. Assuming they started with exact copies of the pieces of that antenna, the manual should lead you by the hand to assemble those pieces into a good enough copy of the original to equal the performance advertised. A low cost antenna is no bargain if you cannot properly set it up for peak performance.

What should be height of ADS-B receiving antenna? The range is basically determined by height of the aeroplanes which are several thousand feet high. However the receiving antenna should be high enough for low flying aeroplanes, and to overcome obstructions of terrain (such as tall trees, buildings, hillocks etc). In many cases, a tower isn’t necessary. When you think “tower”, remember that your house roof may already be a good height already.

One way to answer the antenna question would be to ask, “What does a ‘typical’ ADS-B amateur use?” There is no ‘typical’ ADS-B station; any more than there is a ‘typical’ amateur. However, given the same engineering problem, the solutions tend toward a common theme. Some ADS-B amateurs, who routinely receive ADS-B, have a tower. The most common height is in the 60-70-foot range. On the top of the tower is mounted a 0.5 to 1.5 meter antenna. There is then a coaxial cable running into the receiver. Is this the “best” antenna? Not necessarily. Many amateurs have to compromise this arrangement due to zoning laws, and deed covenants. This arrangement may not be possible in all locations.The best antenna for you will be as personal as the best pair of shoes would be. Simple, easy antennas are a smart start. You can start with a dipole (1/2 wave or full wave or 4 or 6 element franklincollinear). More elaborate (and expensive) antennas should be carefully researched. The experienced Amateur should be able to decide what limitations his or her own situation imposes on the potential choices.

Objects and landforms in the environment profoundly affect radio waves arriving at an antenna. Will the antenna be ground mounted or elevated? Close to a building or in the clear? Mounted on a tower, pole, building? How much will the whole installation cost? Will the neighbors (or spouse) object?

The antenna system is the single most important component of an ADS-B receiving station. It defines the performance of the entire station. Consider the choices carefully, because only you can really answer the question:
What is the best antenna?

***Adapted and modified for ADS-B by abcd567, from an article written by Amateur Radio Operator NM7R for ham radio amateurs.

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hi abcd,

this thread is a really good idea - and your starting post was great! as you already know i did some antenna testing too- but never tried to built one myself. over the last months i bought 7 professional made antennas (4 different types) and 7 dongles (2 different types):

  • flightaware 1090 26" link
  • wimo gp-1090 link
  • baz flu-sr y 13 yagi link
  • jetvision sco 1090 mcx link
  • jetvision a3 ads-b link

my finding was that the best receiving universal ads-b antenna is the jetvision a3 ads-b.

but what i never tried myself and always was really waiting for is a test selfmade vs professional made. in other words i’d find it extremly helpful to know how these different homemade antennas compare to e.g. the well known and widespread actual flightaware antenna?

thanks in advance
tom

edit: did not want to mess up your thread with lots of large pictures - so - here a small one with the ads-b mess that is left over :slight_smile:

https://dl.dropboxusercontent.com/u/39745369/adsb_mess.jpg

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@TomMuc:
Wow! You have a nice & big collection of antennas & other adsb stuff!

this is just mess that is left over after all testing. the ‘real stuff’ sits on my attic and collects data for flightaware :slight_smile: but sorry - my intention wasn’t to hijack your thread with my dumb picture. especially as i’m really curios about all this antenna-homebuilding thing. and as said before i’m hoping to see here some posts about one to one tests - self-built vs flightaware …

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If you even want to liquidate some of the that extra stuff Tom… :smiley:

:slight_smile: yep - of course i’ll sell these parts the next weeks at ebay.de. but the flightaware antenna + pi will ship near to you as one of my best female friends has a house with not too bad view down to lax. flightaware team crashed my stats with their new weird ads-b counting so i have to look for oversea alternatives :)))

For me the “best antenna” was the one that I was prepared to pay for installation on my house. That cost me more than the cost of the antenna and hence before installation I had to check independent reviews of its construction quality and performance.

Not much point in making my own for not a lot of money but then finding it stops working and costs me another fitting charge to replace it. :angry:

I never had a professional antenna, so I did not have an opportunity to conduct professional vs diy test. Those who have used both can answer this. The only thing I can say is that since the diy collinear antennas have a wide degree of success/failure, be ready to get all sorts of conflicting answers. Also failure rate for diy collinears being much higher than their success rate, more answers saying professional antenna is superior are expected.

My experience is as follows:
(1) All of my over a dozen collinears (coax & wire) have failed, except an impedance matched coco & a 4 element Franklin. Even these non-failed ones are only at par with my Cantenna.

(2) With a diy 1/4 wavelength groundplane (spider & cantenna), I can get planes upto 200nm in most directions, and 250 nm in my best direction. Adding an amplifier boosts the plane count by 25% and maximum range to 250 in most directions & 275 nm in best direction. I am satisfied by this, and dont feel any need to purchase a professional antenna. However I am still tempted to purchase a professional antenna for experiments and for comparison and benchmarking.

totally agree - and that’s why it would be interesting for me to know - whether i could improve my site using one of these homemade antennas. sadly canada is so far away and shipping forth and back costs that much - otherwise i would have sent one of mine for some month testing at your home …

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I really do enjoy reading your antenna experimentation on all the forums. Very well executed and methodical testing is the part of the hobby that leads to great satisfaction when things work really well, or work at all.

Sometimes they even fail miserably, like my well designed, well measured, sturdy, ‘should be perfect’ Franklin that underperforms a groundplane made of a connector and four pieces of copper wire. I have another name for it now, that also starts with the letter “F”. :neutral_face: Maybe it’s just that it doesn’t work well indoors…

“If there was just one “best” antenna, everybody would use it. The best antenna for one particular situation may not work well somewhere else”

The quote sums it up well.

I don’t understand why some have trouble building the collinear antennas. We have not experienced any significant problems building them.

Our regional team has gone through several iterations in the past year and recently decided to standardize on 20-24 segment collinear antennas.
You would have a problem fitting them in an attic.

When possible, we will use the antenna with no amplification.
Amplification is used for the longer cable runs.

Our experience has been that in general, more amplification is better excepting use with the Flight Feeder box with the Nuand receiver. It will chop off high power signals (losing nearby aircraft). Only apparent problem with amplification is it adds components to the system that can fail.

We compare antennas by looking at the Positions/ADS-B aircraft ratio.
Flight Aware used to include it in the statistics page but, regretfully, eliminated it in their latest web page revision.

The Flight Feeder antenna works fine (we have a couple) but 12+ element home built collinear antennas have better performance.

Now, we are working to optimize the amplification system. Power injectors and amplifiers are not all equal. We have a pending manufacturer inquiry on current availability of the amplifier that meet our needs (voltage, gain, noise, frequency and cost).

High gain antennas are mostly collinear antennas. These fall into 3 types:

(1) coaxial collinear, made of pieces of coax cable or tube & rod.

(2) wire collinear, made of pieces of wires with intermediate coils for phasing.

(3) franklin collinear, made of pieces of wire with itermediate hirpins (stubs) for phasing. It a has a central hairpin (stub) for impedance matching. The feed cable is connected to a point near the end of stub. This point is to be found by trial 7 error, watching for the best output.

All above collinears are dimensionally intolerant. Few mm error in DESIGN or in CONSTRUTION throws the collinear from “excellent” to “poor” category.

Often designs are posted on internet, backed by simulation results giving high gain of the order of 5 to 9 dBi, and a beautiful lazy 8 (https://upload.wikimedia.org/math/d/2/4/d245777abca64ece2d5d7ca0d19fddb6.png) radiation pattern, with software optimzed dimensions. Mostly these are flawed design. The reason is that for comples antennas, the simulation software give an error of about ± 10%, which is far too large to be tolerated by a collinear.

There is an additional problem with coaxial collinear, the TRUE Velocity Factor is not known to most diy, and even the figure given in specs is an average value. This introduces an error in element length which is far more than the tollerance limit of coco.

The Collinears are therefore difficult to design if the Amateur doesn’t have a background in engineering, and difficult to tune after construction if the amature lacks key pieces of test equipment.

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This is another generalization that is just not true, sorry. It all depends on the LNA inside the receiver and the additional amp in combination.

Even, if the combined amplification is the same like without the amp, performance can hugly increase, because of overall lower noise:

https://en.wikipedia.org/wiki/Friis_formulas_for_noise

Again, you amp can decrease your stats, but another amp with lower S/N can boost your stats, even if you overall gain of the chain is the same (or even lower!) than the maximum gain of your SDR-built-in LNA-gain.

Gain is just the half truth, noise is the other half. You always have to look at the combination of both of them.

Kabuse

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‘should be perfect’ Franklin

Yes I tried one of those and quickly abandoned it. Not sure what I did wrong but had much more success with spiders and co-linears. Need to define the performance of those - at the moment it is just an empirical “not bad” :smiley:

Absolutely true on aystem gain and noise. But I was describing what we do with our systems which is not a generalization.

This is my best antenna -> f5ann.pagesperso-orange.fr/Anten … index.html
I have built more than 30 antennas of different designs.
This is my rating:
Stock - 1/10
Faranklin (several variants) - 3/10
Spider - 3/10
G-7RGQ (and variants) - 3/10 (max)
Coco (several variants, only a coaxial cable) - 6/10
Coco (H1000 coaxial cable and copper pipe 10 (?) mm, several segments) - 7/10 (but at Elonics E4000, was destroyed by many changes)
Strip-line1090 first - 8/10 (I use it)
Strip-line second - 9/10 (I use it)

Many Coco antennas has not worked as I expected.

Strip-line1090 at work (antenna has a limited view)
http://screenshootereu.blob.core.windows.net/engine4files/edavqyzhjdbpcjirssfydyiwxiicwoafqqdyshfwhzbbsmpfpbqlqgkmvrtnodsugwitvrxcvoyzgidcipkijcqjmxtavoljxiyg
I’m going to make a new Strip-line1090 using the microwave laminate (copper clad, has stable permittivity).

Sorry for my bad english (I limit myself to reading of posts).
Best regards to DIY and fans of aviation.

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Are you making the single element (15cm) version? (And your English is fine, I had no problems understanding you…)

Can you post some dimensions and the brand of coax cable used for the successful coco’s ??
I made another coco a couple of days ago and its as bad as all the rest :cry:

@yooshky, Good to hear the f5ann PCB active antennas work well, I was looking at the web page the other day and thinking about making a copy on FR4 and using a PGA103 LNA as I’m familiar with them and they are easy to get here.
Do you think its worth while trying the FR4 or is it absolutely necessary to use the microwave rated (and difficult to get) laminate

My antennas are made of double-side FR4 (thickness 1.5 mm, ε=4,8???). They work good. I have built with soldered segments. Microwave laminate has a stable dielectric permittivity (constant on the whole surface). But a good teflon laminate in the PL is priced as factory ready antenna :slight_smile:

I would not even know where to start looking for teflon PCB but I have the double sided 1.5mm FR4 here that you have used so I’ll give it a try.
Must order some more PGA103’s amplifiers, I keep forgetting how static sensitive they are :blush: