FlightAware Discussions

Antenna advice Discone Vs Collinear and some issues

It depends on your location. Germany pricing is 59 Euro for the FA antenna and 77.95 Euro for the Jetvision, so less than 20 Euro in difference.
I decided to get the Jetvision because this 20 Euro difference did not matter to me, other are paying thousands for their classic cars as hobby :slight_smile:

As @wiedehopf stated, the FA should be fine as well without a recognizeable difference

Airnav Systems is also selling their ADS-B Kit Antennas with a fixed cable mounted on it. Not sure about the performance, but the figures look similar.

Filter is behind the LNA which will get overloaded.

Just get the dark blue FA barrel filter unless you want to spend massive money.
Alternatively get the AirNav filter.
https://www.amazon.co.uk/AirNav-RadarBox-1090-ADS-B-Filter/dp/B082WR1SDF

AirNav filter is probably narrower but not as low insertion loss.
I’d probably use the FA barrel filter.
(and then try with and without, pretty much the only way to reliably find out if it’s beneficial)

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@foxhunter
Thousands on classic cars, I don’t know what you mean… :slight_smile:

Here’s an event I organised for 35 vintage Bentleys and, a masquerading XK120 that’s hiding two Talbot AV105

Me navigating in a Hillman Imp and a Austin Healey 3000…

Forget it, stupid idea to start this discussion :rofl: :joy: :rofl:

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:smiley: :smiley: :smiley:

I’ve got the Jetvision and Airnav one.
From my small test, it seems like the Airnav one is performing better. I have 2 Pi’s running side-by-side. There isn’t much flighttraffic over Denmark in the weekends, so i’ll swap antennas during the week to see the difference.

Notice the DHL5AC flight… RSSI ~8 dB is the Jetvision antenna. I swapped to the Airnav and get ~2dB2020-05-14 17_16_43-Window

2020-05-14 17_18_58-Window

not comparable. The moment you swap the antennas also the aircraft positions changed.
You will need to have two receivers set up side by side to perform a reliable comparison

It also depends on the cable you’re using (same length, same quality)

It’s repeatable, i’ve tried several times - But as said, i’ve got two Pi’s now so it’s easy to test.

The cable is the standard from both vendors. The Airnav one doesn’t have a connector, so it’s impossible to swap cables.

That’s what i said… Not comparable
Cabling should not be underestimated

I agree… But most buy the antenna and cable as a kit. So best bang for the buck is comparable.
Anyway, i’ve ordered an Uputronics LNA more, so the setup would be the exact same, just different antennas.

A discone is a bad idea since it will pick up more out of band signal.

Most of these 1090 antennas are based on cookie cutter designs scaled from the ARRL handbook. With one exception, I never found one that was modeled in NEC2.

These colinears look good on paper. Trouble is they will have nulls in the reception and these will not be found logging your most distant hits. In my opinion for what is commercially available, I would get a simple half wave monopole and call it a day.

Note that no monopole will beam to the horizon let alone beneath it. I have a folded dipole design fully modeled in NEC2. I find the impedance match to be troublesome. The quarter wave didn’t work at all. I have a exponential taper match kind of working but it looks too bulky. I will try a Klopfenstein match, but the math looks ugly.

The 1090 I saw NEC2 modeled was based on
https://martybugs.net/wireless/biquad/
This will beam to the horizon but it is directional. Of course given the cost of dongles these day it might justify have multiple antennas/receivers if you are gonzo enough.

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The reflection coefficient is pretty high below 10GHz.
For a receiving antenna, will you get a net benefit?

Are you reffering to SWR?

If you use a the filter can, you want the impedance to be on the money.

My confusion with your comment is why would I want a poor match?

No, I was referring to “Reflection Coefficient”

image

Return loss registered with my brain. SWR can be derived from return loss. But why wouldn’t I want an optimal match?

Note the lack of a good match with the exponential taper I ran could be the fault of the NEC2. I made a spreadsheet to generate as short as feasible wire segments, which is suggested for transmission lines. You have to exceed 6x the wire radius. The SWR was around 1.4 with a 0.07meter long taper. Of course you could bend this wire.

Life is much easier just scaling a design from the ARRL antenna book and pretending it is optimal. NEC2 is a pain.

I know there are people much smarter than I here in these forums (and in this thread for that matter), but I think much of what you all are going back and forth about is much more important for an Rx/Tx setup, not so much for an Rx only setup for ADS-B. Computer model vs. real world are two totally different beasts from my limited experience.

That said, I think it’s important to look at different models than what we’re currently presented with in the open retail market for lack of better terms - as there are plenty of different avenues and designs that are highly effective as a whole (depending on location of course), but most alternatives I’ve seen are more directional by design such as the above. Given the modeling and/or general radio experience of some of you, what would your conclusions be as another avenue for the masses to follow as it pertains to omni-directional efficiency? What may be optimal for me may be the opposite for someone 1000 miles away…

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I’m not suggesting anything of the sort.
(If it works and demonstrates a significant improvement, I’ll build one myself - I’m just skeptical)

As I read the graph, A Klopfenstein / Dolph-Tchebycheff match won’t perform well under 10GHz.
If you disagree, I’d like to see what you have built and hear how it performed.
(and compare that to ‘not using it’)

Thanks for all the input.

FlightAware antenna has arrived, awaiting N type connectors now.

@abcd567 mentioned about the dark blue 1090 filter, can’t find one for love or money!

Kev

I bought it recently in an online shop in germany for around 20 Euro. But i don’t know the shipping cost outside of Germany

Thanks to @foxhunter for his help in obtaining a filter. I’m waiting for some N Type connectors to rig the FlightAware antenna up and hopefully raise it a little so it will be above the apex of the roof.

Filter is installed and I’m seeing some slight differences already, I’ve been able to track a flight at 36000 feet up to the Isle of Man, not broken the elusive 100nm barrier yet on a track that I’ve viewed.

Will update as progress allows, I’ll do a heatscan with the filter in place to compare before and afters.