REVIEW: ADS-B Receiving Station

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An ADS-B receiver using a Raspberry Pi B+ / FlightAware Pro Stick Plus combination, reports on the Es’hail-2 geostationary satellite, revisits the Anytone AT-868 and revisits the PMR446 band.

Reviewed by: Tim Kirby

Setting up a FlightAware ADS-B Receiving Station

 

Readers who were with us last month may recall that I discussed how to set up an ADS-B receiver using a simple RTL-SDR dongle and antenna. A week or so ago, our editor emailed to say, would I be interested in trying one of the FlightAware ADS-B dongles? “Yes, please”, I replied!

https://uk.flightaware.com

Yesterday, the postman delivered a box containing a Raspberry Pi B+ computer and PSU, a micro SD card, a FlightAware Pro Stick Plus with amplifier, a FlightAware 1090 ADSB filter and a Moonraker MRM-1090 Receiving antenna (Figs. 1 to 3). 

Pictures: Tim Kirby

The FlightAware Pro Stick / Raspberry pi / Filter Assembly.

The FlightAware 1090 ADSB Filter.

The Moonraker MRM-1090 Receiving Antenna.

I unpacked everything and was keen to get started. The micro SD card was shipped in the appropriate slot on the Raspberry Pi. Popping it in an adapter and into a slot on my laptop, I could see that there were files on it, but none to boot a Raspberry Pi! No matter! All the instructions for the setup are at this URL: https://flightaware.com/adsb/piaware/build

 

Just follow the instructions, but in short, you will download a zip file from the FlightAware website onto your computer. When unzipped, this is an ‘image-file’. You will then use the Etcher utility (also linked from the instructions) to write to the micro SD card.

 

After this, you should insert the latter into the card slot on the Raspberry Pi.

 

If you haven’t done this before, don’t worry – it is very simple; there are instructions for both Windows and OS X computers! The only thing to be careful of, when you are writing the image, is that you write the image to the correct disk, i.e. the microSD card – otherwise things might go a lot wrong with your laptop or computer!

 

Almost done; the only thing remaining for configuring the Raspberry Pi was, with the microSD card in my laptop, to find and open the piaware-config.txt file, locate the section regarding Wi-Fi and replace the details in there, with the name of my Wi-Fi network (the SSID) and the password. Save the file and you are done!

 

Insert the microSD card into the Raspberry Pi and connect the PSU to the Pi. For the first boot of the system, it’s probably easier (though not essential) to have a screen attached to the Pi, so I used an HDMI cable into the HDMI connector on the Pi. Connect the antenna into the ADS-B filter, then the filter into the Pro Stick Plus, and, finally, connect the Pro Stick Plus into a USB connection on the Pi.

 

Powering Up the System

 

You are now ready to power on the machine. You should see some activity on the screen, along with some instructions. There is plenty of useful information here, but the most important thing is that you will see a URL displayed that you can use to connect to the computer from another machine on the same Wi-Fi network. This allows you to ‘claim’ the receiver.

 

What this means is that you will set up an account on the FlightAware website’s log-in page and ‘associate’ the receiver with your account. This way, you will be able to see all sorts of statistics about how well your receiver is performing, by means of using the My ADSB section of the FlightAware website.

 

You should also spend a little time setting up the Multilateration (MLAT) feature. This means that your receiver can help triangulate positions of aircraft, which are not broadcasting their position, or which are not equipped with the latest ADS-B technology.

All you need to do this is to pick your position on a map and set it. You’ll also be asked to enter the height of your antenna above ground.

 

By now, even with the antenna on the desk in front of you, it’s likely you will be picking up some aircraft positions. From a laptop, phone or another computer on the same Wi-Fi network as your Pi, go to the IP address that your Pi displayed. You should see a web page which will say Go to Map. Click that, and you should see a nice web page showing a map (you’ll need to ‘centre’ it on your location), as well as a list of aircraft, and some details about those.

 

Next to being displayed on your screen, these are also being uploaded to the FlightAware system.

 

You can now have some fun positioning your receiver and antenna in the best possible place. Because the Pi is now fully configured, you don’t need to have the screen connected, so you can move the computer and receiver to anywhere in your house where there’s a power socket and where things are within Wi-Fi coverage.

 

Spotting Aircraft

 

First of all, I decided to locate the receiver in an upstairs window, facing west. It was immediately obvious to me that the receiver was picking up more distant aircraft than my previous setup. I guessed that this was down to the antenna more than anything else. The Pro Stick Plus is based on the same receiver chip as the RTL-SDR, although it has an additional filter stage.

 

However, I was seeing plenty of aircraft out to at least 100 nautical miles to the west and north of me and also found some surprises, especially to the south, picking up aircraft at over 200 nautical miles away (Fig. 4).

Screenshot of the Receiving System in Operation.

Noting that the ADS-B bandpass filter had an insertion loss of around 2.5dB, I wondered how this affected which aircraft I was seeing. Removing it, I did start to see one or two more aircraft at a greater distance.

 

However, the lack of the filter (Fig. 2) was apparent as soon as I started transmitting on 144MHz, when reception of ADS-B signals went down, dramatically! So, if your location is anything other than quiet, RF wise, you’ll probably want to install the filter.

 

I moved the receiver to the greenhouse at the end of our garden (probably not ideal in the summer months) where I thought that, although the antenna would be lower, it would ‘see more sky’. I was interested to note that I saw many more aircraft, albeit at not such a great distance. Fascinating!

 

Setting the system up as best you can, is very easy and quite addictive; the My ADS-B section of the FlightAware website allows you to see how your station is performing in relation to other nearby receivers.

Overall, I thoroughly enjoyed getting the system going and was delighted to find how straightforward it was.

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If you are not familiar with setting up and using Raspberry Pi computers, you should not be put off at all, because you will be guided through the process.

 

Signals from Space: Experiments with your Sky Dish

 

I have mentioned some of the satellites which can be received on a simple handheld scanner in previous months. A new satellite was recently launched which is very different. It is Es’hail-2, the first geostationary satellite carrying facilities for radio amateurs. The satellite is also known as QO-100 (see also: Practical Wireless, April 2019: 60-62). This, of course, is very different from the low Earth orbit satellites, which I have mentioned before. The latter are generally above the horizon for around 10 minutes at a time, a few times a day, depending on the orbit of the satellite itself.

 

Es’hail2 carries two amateur band transponders, one narrow band and one wide band. The downlink for both of these transponders is on the 10GHz microwave band, with the corresponding uplinks in the 2.3GHz (13cm) band. An immediate reaction from people is that it’s microwaves so it must be hard to receive. Actually, the reverse is proving to be true, and many people have been ingenious using conventional satellite TV equipment feeding into an SDR receiver to receive the signals.

 

If, for example, you have a Sky receiver connected to a dish, and which has a Low Noise Block (LNB) and multiple feeds from it, then you should be able to receive signals very easily indeed. Leave the Sky Box connected to the one feed. This sends voltage up to the coax to power the LNB. If you have a spare feed, then disconnect that (temporarily, perhaps) from whatever it may be connected to and feed it into a receiver, perhaps an SDR or a communications receiver, tuned to around 739.675MHz.

 

Although your Sky dish is pointed at the ‘wrong’ bit of sky, the Es’hail-2 signals should be strong enough for you to receive. What are you listening to? Signals will probably be SSB, with some Morse code. There may well be data signals. There is plenty of activity, so you should be able to tell pretty quickly if it is working.

 

If you do not have a spare feed from your Sky dish, you can probably still use the same technique, but you will have to disconnect the Sky receiver. Because the receiver sends power to the LNB through the coax, you will have to use a Bias-T arrangement, which you can either build or buy, to inject the required voltage, 12V DC to power the LNB (note that if you send 18V to the LNB, it uses horizontal polarisation; if you send 12V, the LNB receives vertically polarised signals. For the narrowband transponder, we want vertical polarisation, so you can use 12V DC.

 

If you don’t have a Sky dish, then you can buy an LNB. You may not even need a dish. However, if you can find one, it will help. If you would like to read more about how to do this in much more detail, there is an excellent article, written by Dr George Smart, who has described the whole process in great detail and should help you set up your ES’hail-2 receiving station:

https://www.george-smart.co.uk/2019/02/eshail2-rx

 

You can find out what it all sounds like, before you go to the trouble of building your receiving station, thanks to an online WebSDR located at the Goonhilly site in Cornwall. Point your browser at this URL: https://eshail.batc.org.uk/nb

 

You will be able to tune across the satellite and listen to the amateur stations using it. I have just listened to a station in England having contact with a station in Mauritius. It is proving quite interesting to see where it is possible to use the satellite from. Stations in the north of Brazil report hearing the satellite, and, of course, if you use a larger dish from remote locations, then you stand a better chance of hearing a useful level of signals. I have also been following, on Twitter, the experiments of an amateur in China making his first contacts through this satellite.

 

Along with the narrowband transponder, there is a wideband transponder, which some amateur stations are using to transmit television pictures. You can receive these online as well, using the British Amateur Television Club (BATC) streaming feature on its website.

[See the profile of the BATC in RadioUser, April 2019: 30-33 – Ed.].

The exact URL will depend on who is active at a particular time, but if you browse to the website at the end of this section, you may well be lucky and be able to see some amateur television being sent via the ES’hail2 satellite:

https://batc.org.uk/live

 

The whole system has resulted in some ingenious setups. Some stations have been using Wi-Fi booster amplifiers and antennas for the uplink, driven from a very low power transmitter to a simple helix or antenna made out of PCB. It’s fascinating.

I hope you will enjoy listening online, and I will be very pleased to hear from readers who are successful in ‘repurposing’ their Sky satellite equipment, especially those who do it without causing domestic disharmony!

 

More on the Anytone AT-868 as a Low-Cost DMR Scanner

Readers may recall the item on using a DMR rig like the Anytone AT-868 as a budget digital scanner in last month’s issue (RadioUser, April 2019: 39-41).

I was very interested to hear from Mike B who wrote in to say that he had since learned that both the Anytone AT-868 and 878 are able to monitor all RAS enabled systems, with the exception of Mototrbo CAP+ systems with RAS enabled.

 

I am intrigued by this. Where I live in rural Oxfordshire, the options for digital scanning are pretty limited to amateur DMR transmissions in both the 145 and 430MHz bands! Digital monitoring on the AT-868 works well for this. Under the Digital Monitor settings, don’t forget that you can have the rig scan BOTH timeslots, rather than just one, along with having it scan across all colour codes and IDs.

 

If any readers have tried digital scanning with their AT-868 or with the newer model (AT-878), and have been able to decode non-amateur transmissions, it would be very good to hear from you and learn the type of systems and traffic that you have been able to monitor.

 

PMR446

Most readers, will, I imagine be familiar with the 446MHz PMR band and the handheld radios available for the band. I confess I have not used it as a target for scanning for some years. Here in the ‘sticks’, the majority of traffic is domestic, although I’ve heard motorcyclists in convoy talking to each other down one of the local trunk roads and a DX Net on a Sunday afternoon.

 

My experience with PMR446 so far has been analogue, but I was interested to see that from early 2018, there is the potential for digital users of the band with both DMR (Tier 1) and dPMR permitted.

The DMR channels are the same 16 12.5kHz channels as the analogue channels, with the lowest frequency at 446.00625MHz; dPMR has 32 channels at 6.25kHz spacing, with the lowest frequency at 446.003125MHz.

Clearly, there is a possibility for these systems to interfere with each other! However, since the purpose of the devices is generally agreed to be short-range communication, and given the number of channels available, there is the possibility to reduce mutual interference.

 

Channel 8 (446.09375MHz) is often used as a ‘DX’ channel, predominantly on analogue, although I would guess trying it in digital mode would prove quite interesting! Channel 1 is probably more heavily used because many people switch on the handsets and do not change the channel. Whether you decide that is a good channel to scan or to skip, I will leave with you!

 

If you are within range of the South Coast of England, there is a net on most Monday evenings, between 2000 and 2200 local time on Channel 8, which you may find it interesting to listen to and see which stations you can hear. Stations use a variety of equipment from different locations so you may well hear something if you have a listen. I am sure there are other nets – see what you can find and let me know!

 

That’s it for this month! Hope to see you next time.

 

My warm thanks – and those of the editor – go to Chris Taylor, Head of Retail at Moonraker, for the loan of the ADSB receiver review equipment.

 

 

This article was featured in the May 2019 issue of Radio User.