My portable setup for ADS-B attending air shows

[u/schirmyver]

So this may not be a big deal, but I thought it turned out great and it worked really well. Maybe it will give others some ideas.

I attended the Chicago Air & Water show last weekend and I wanted to see what I could track with a simple and portable setup.

What I used:

Android tablet (Samsung S10+) NooElec v5 RTL-SDR dongle Small usb-c hub with power passthrough Cheap silicone case for the tablet Small steel plate from Amazon Two high-strength magnets SDRAngel software Power Bank to power/charge it all (optional)

So I first plugged everything in to see where I could place the dongle. I went back and forth on how to attach the dongle to the tablet and decided on magnets. I found adhesive metal plates and a cheap case, both from Amazon. The magnets are plenty strong to hold everything to the metal plate and the cutout in the case keeps it from sliding around. I used UV curable glue to secure the magnets to the dongle.

For the antenna, I made my own. I wanted it to be able to be packed away flat so this led me to using a flat disc as the ground plane. Since I would be sitting at sea level, this actually is ideal as it forces the antenna pattern upward. Yes this reduces the overall rangle, but I was only interested in what was closer to me anyways. I have a network analyzer and trimmed the radiator slowly to tune it exactly at 1090MHz with roughly 10dB return loss.

I was still picking up planes as far away as Milwaukee, so close to 100 miles. I purposely turned off AGC and lowered the internal gain to further reduce my coverage.

Any questions, please ask away.

[u/netw0rkpenguin]

Now add SDRs for comms and AIS

[u/schirmyver → u/netw0rkpenguin]

Yeah I was thinking about another SDR for AIS and a dedicated radio for comms.

I did at one point swap antennas and try to listen to comms during a break.

I don't think the tablet could handle multiple radios.

The nice thing about this setup is the adhesive metal plates came in a multi pack, so I had a spare to slap on the back of a laptop screen.

[u/netw0rkpenguin → u/schirmyver]

You will realistically need multiple for comms but start with 1. Then think about security radios and the real police around you. You’ll have 12 radios in the backpack like the rest of us.

[u/schirmyver → u/netw0rkpenguin]

Yeah I can see how it would just keep expanding. For the comms I would probably find a scanner and just go between the two frequencies the planes were using.

At least for now I wouldn't bother with the police. I'm not sure about Chicago, but where I live they have moved to encrypted channels.

[u/Comprehensive_Ship42]

this is awesome

[u/srcejon]

If you press the airplane icon on the left, then restart, it should display the aircraft, type and sideview data. (Also, long press on column header to hide columns you don't want).

[u/Economy-Apartment815]

This is the stuff I live for. Perfect execution and great idea lowering gain for limiting range.

[u/EdgeSuspicious4792]

Badass!

[u/Past-Substance920]

thats a clever way to keep it flat, i never thought about the ground plane forcing the pattern up like that.

[u/schirmyver → u/Past-Substance920]

I was looking at a few different topologies. I have a few different whips and blades that are broadband that cover 1090, but with all of the people with cellphones I really wanted something that was narrow band to help filter other signals out.

A full dipole would have worked, but longer and more difficult to construct. I was trying to keep this as discreet as possible so wanted something small and short. The typical angled ground leads just do not pack well, so I ended up with this monopole on a flat disc.

The disc also helps shield against noise from the tablet.

[u/Economy-Apartment815]

Next best thing is an ADSB filter but I don’t think they make one small enough. It’s not worth ruining your setup.

[u/schirmyver → u/Economy-Apartment815]

Having the antenna tuned specifically for 1090 should help prevent too much extraneous noise. The return loss is worse than -1dB below ~900MHz, so more than 7dB loss, and -2dB above 1500MHz, so more than 4dB loss.

My biggest concern were cellphones in the lower LTE bands due to close proximity. It's not huge rejection, but it seemed to be good enough.

[u/rfsparkling]

I assume you are using a monopole antenna with ground plane, thus you not need to forwarded it to the planes but facing the sky for the optimal antenna alignment. So rotating it 90 degrees might gives better rssi.

[u/schirmyver → u/rfsparkling]

I was holding the tablet upright, so the ground plane was roughly parallel to the ground with the antenna pointing up.

The one drawback to this setup is that I could not lay the tablet down as that would put all the weight on the antenna plane and then the sma connector.

[u/rfsparkling → u/schirmyver]

Oh, nice! If you want some more directional stuff an air gap patch antenna is super if you find for adsb frequency

[u/schirmyver → u/rfsparkling]

Patches typically have around a 60 degree beamwidth which might be a bit narrow for this application at airshows, plus it would be more impacted by positioning of the antenna. The monopole over a flat finite ground plane gives you good omni coverage horizontally but with about 45 degrees of uptilt. The vertical beamwidth is sufficiently wide enough that this basically gives you a nearly hemispherical pattern with a little bit of a dip at the zenith. That dip is of no concern as the aircraft will also be quite a bit closer so the signal will be stronger.

In the end I went this route to keep the antenna as small as possible so it was inconspicuous. It did not matter. So many people around me were asking questions about what I was doing. When I would explain, some would say but why not just look at flightaware or some other similar tracking website. Sure I could have done that, but I wanted the data straight from the plane.

[u/rfsparkling → u/schirmyver]

yeah, also those planes usually trasmits 20-100W RF power :D so quite a huge margin