FlightAware Discussions

An Introductory Note About DIY Antennas

2nd pair of PCB antennas arrived today from Singapore (20 days after ordering) and they check out decent on the analyzer = 45-ohms and VSWR ~1.2 …

The PCB is 170mm long without the connector.

My one is shorter than that because the bottom half of the dipole is much closer to the connector. It’d be interesting to see if the longer one with the slightly larger trace works any differently. In theory it shouldn’t.

Was it fully soldered?

Yes, both the whip and ground plane connections were soldered on the front side. The longer PCB has solder vias that connect the traces on the top and bottom side of the PCB. The shorter PCB does not and the shorter PCB only has the ground plane on the backside where I had to solder the connector lead to the ground plane.

The PCBs-in-tubes showed up today (15 days after order placed) and they tested out good on the analyzer so I cut the tube end off to inspect the PCB.

It’s identical to the short PCB above except for 2 things:

  1. the Ground plane connector leads on the bottom side were correctly soldered
  2. the 2 Ground plane traces have copper antenna extensions (apparently trimmed for 1090MHz)

The copper extensions (~2mm) appear to be soldered on after someone scratched off the green coating at the ends of the traces. That 2mm is probably enough to re-tune the antenna sweet spot from 1160MHz to 1090MHz.

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Performance wise (message rate/plane count/max range) how the short one compare to the long one?

I haven’t used either one yet - only tested them with the impedance analyzer.

And they claim 6dBi for that. It’s a dipole. The most smegging gain it can have is 2.15dBi or 0dBd.

BOGUS CLAIM

It is PCB version of “koaxialantenne” (coaxial antenna aka coaxial dipole)

Translation from German to English (in red) added by me

I’m a bit confused by your diagrams.

You have indicated the transmission line on the PCB dipole is Flat Coax but it is not coaxial at all. The outer conductor is not a tube surrounding the inner conductor. From the picture it looks more like micro-stripline.

Also, in this picture


you refer to the lower half of the coaxial dipole as a Decoupling Sleeve whereas it is actually part of the dipole.

The implication of the diagram is that the Cantenna is better than the Coaxial Diploe because it has a full λ/4 ground plane rather than just a Negligible Ground Plane and it has “Low Loss + low capacitive current” rather than “High Loss + High capacitive current”.

The implication from the two diagrams appears to be that the so-called Cantenna which is a λ/4 ground plane with a skirt operates in the same mode as a (coaxial) dipole. The radiation pattern of a ground plane antenna and a diploe antenna are different and their effectiveness differs in differing circumstances. That is why reputable manufactures provide tested technical specifications for each of their products.

S

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25dBi (twenty five dBi) antenna for £1.98+Free postage :wink:

https://www.ebay.co.uk/itm/382563638137

Is that a special way you have to bend the coax so you get the advertised 25 dBi?
Intriguing.

Maybe you can harvest zero-point energy with this antenna as well?

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The secret is the PAL plug.:grinning:

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No, that’s just the signal pulses passing through the cable :wink:

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I laughed but with my more serious hat on, it does mention a supply voltage and an amplifier.

In case anyone is even considering buying this… don’t!

Damn, does not post to Germany :smile:

To be fair, it might just be a typo, it says 5Dbi, on a smaller picture and probably is fine for watching TV :wink:

Read the text now, there actually are active dvb-t antennas with inbuilt amplification, but they do not look like this, maybe someone copy-pasted different stuff together…

Yep…and digital, note the transitions.:rofl:

Hello everybody,

i started my little project on participating in the tracking network two days ago.
I am using a Raspberry P3 together with the FA Pro Plus stick (the blue one) and a simple indoor antenna which is for the 1090 MHz frequency range optimised out-of-the-box

All works fine with the FA Image. The receiver antenna i have placed on a cookie can (similar as shown above in my home office room on 2nd floor close to the window.

So far it is working, the range i usually get is constantly up to 100 NM with some peaks going to 150NM or 200 NM

The graphs are showing an average ADS-B signal level in average of -16 with a peak level of -1.2 over 24 hours.
Is there something to suggest for improving this except getting an outdoor antenna (which is currently not possible)?
Does the size of the can has an impact? Any thoughts on where at the window? Higher or lower?

I am living in Germany close to Frankfurt, so the peak number of aircrafts over the day is >100, in reality i’m ok with it.

Thanks

@foxhunter

Just to get an idea what maximum range you can get with an outdoor antenna:

What is the Maximum Range I can Get?

Even if the antenna says 1090 MHz, most of the time it’s not optimized for that frequency.
Almost all such antennas are falsely called 1090 MHz antennas.

For whip antennas, i haven’t encountered a case where the performance didn’t improve when cutting them to length:
How to improve performance of whip antenna of DVB-T

If you are using one of the nooelec antennas, those are very very bad. (unlikely with your range)

Thoughts on optimizing gain

Welcome to the hobby.

As @abcd567 said, you need an outdoor antenna to get maximum range.

If you look at the bottom of this page you will see your statistics and that of your 24 neighbouring Flightaware receivers.

Over a day you received 1,205 flights and 62,430 positions.

Over the same day seltsam (12 miles from you) received 3,924 flights

and

backi (who is 19 miles from you) received 845,103 positions.

If you have a good, external antenna that is not shadowed by terrain, buildings etc and your receiver/coax/filter/amplifier etc are appropriate you should be able to receive similar numbers.

Everything you compromise in the antenna/receiver/coax/filter/amplifier will reduce those numbers.

Have fun,

S.