Easy ADS-B (IN)

by Dug Smith

I’d decided that I wanted a moving map GPS in my aircraft, and the little tiny black and white Garmin wasn’t cutting it. Having upgraded from a 2013 Google Nexus tablet, I decided to use that. It has a built in GPS receiver, and the 7” screen isn’t so big that it gets in the way on the panel.
It’s also light enough that I can attach it with Velcro, and the internal battery lasts for hours. I downloaded the Avare app, and pulled in the local maps. The app itself is very configurable, and you can set up flight plans with it.

You should use the download feature every time you fly, as it will pull in available TFRs – you can see it’s got the standing Beale up to 18,000’ TFR
marked in red.

I flew with the moving map for a while, but after seeing the EAA’s cheap ADS-B article, using a WiFi connected Raspberry Pi, I started looking into setting up ADS-B “IN” with my tablet. As it has a micro USB port, I didn’t see the need for a whole extra computer.

Looking into it, Avare supports external software plug ins via an extra add-on app, and there’s an app that will add in the ADS-B data. This is great for testing, but it needs to be restarted often as it’s only a trial. Once I had got it all working, I went ahead and got the full version, which doesn’t need to be restarted.

Having decided on the software, the first thing I looked into was the software-defined radio that actually collects the ADS-B signals. The guy who
wrote the ADS-B software suggests the NooElec Mini 2, and that was a good enough recommendation for me. One thing to be aware of is that the antenna has a magnetic base, and it caused interference with my compass. If you remove the black sticker on the bottom, you can just take the magnet out (it’s just stuck in magnetically, and I was expecting to have to cut it out). I’ve extended the antenna and zip tied it to an out of the way strut.

A short on-the-go (OTG) cable (something such as this) can be used to connect the SDR to the tablet, and we’re off to the races.

Unfortunately, there are two different frequencies. 1090 MHz ES (Traffic) can be very easily received, but is generally only used by the bigger guys who go above 18,000’, and 978 MHz UAT (Traffic / Weather), which tends to not pick anything up from the ground. I use 978MHz, but have yet to be flying in anything like weather that will show up on the map.

ADSB Pro shows the flight details for the aircraft it can see, but who cares about that, we want it on the map. Here’s Southwest 755 coming out of Sacramento, heading roughly southwest at 6750’ (pressure altitude). You can tell by the length of the blue line that he’s moving pretty fast (the list above shows 311 mph ground speed).

You’re powering the SDR from your tablet, so that affects the battery life (you can get OTG cables that you can also plug into power, but that seems unnecessary to me). I run my tablet in airplane mode to turn off the WiFi and Bluetooth radios, and that helps.

As I already had a tablet lying around, my total cost was around $30, but you can pick up cheap tablets new, just make sure they have built in GPS.