Year: 2020

Raspberry Pi4 Remote Mount ADSB Receiver.

I know I am late to the party as ever, but I wanted to try and increase my knowledge of the Raspberry Pi and Linux so decided to try my had at 1090 MHz ADBS reception.

I wrote up some initial thoughts in a previous blog, this was my attempt to improve the reception and remote mount the Pi close to the antenna.

The problem with traditional deployment is the antenna and SDR receiver (FlightAware) are mounted some distance apart. High quality coax is needed, and even then the losses at 1090 MHz are high. I calculated 10 m of RG213 would equate to at least 3 dB loss, my antenna would need 25 m or coax to mount it in a convenient location. Factor in connectors and I was looking at a 9 dB loss, close on 90% or my received signal lost in attenuation.

The Pi has WiFi, and previous tests had shown me the range and reception was very good, so the idea of mounting the Pi in a waterproof box close to the antenna was conceived. Its not new, im not the first but this is my process and lessons I learned.

The rule of thumb in a box, is think of a size then double it, its not the pi that causes the issues, that is small.

85 mm x 56 mm in new money.

Its the routing of power, USB, SDR and the coax socket that need some consideration. Cooling may also be an issue, a sealed box could get very warm in the summer without some fan and ventilation.

Box options, I selected something marked waterproof and 150 x 110 x 70 mm and it cost £6.25 delivered.

Next was some waterproof sealant, I was going to be drilling holes in the box, and some waterproofing would be required. A tube of Silicon bathroom sealant seemed suitable. I would use this to seal around the power and coax cable entry points. I was going to be drilling all my holes on the bottom of the box, but everything needs to be sealed

The next issue was around the USB ports, I wanted the flexibility to mount the Flight Aware USB receive in a location of my choice and not be limited to the position of the USB ports.

Right angled USB extension cable

The short extension cable offered the ability to mount the USB receiver flush to the case, with a hole drilled for the SMA to poke out.

USB C Power cable with break out for wires.

Only suitable for short runs of power cable.

Powering the Pi needed some thought, was I going to connect 5v directly onto the board (this would have been easier) of could I look for some way to wire directly into the USB C connector. In the end this connector cause me a few concerns, it worked exactly as described, but in a tight box it takes up and incredible amount of space. If I could have got a right angled version, this would have made for a much neater installation. They are also quite expensive, but needs must.

For longer power cable runs voltage drop will become significant, and so I used a DC to DC converter from PIMORONI. They have one detailed on their website as Wide Input voltage SHIM, and you can power it with 3 to 16v

Wide input DC to DC converter

The last piece of the puzzle for me was a coax cable, I wanted N type on one end to connect to the antenna, and SMA on the other for the Flight Aware receiver.

If you wondered why I selected the blue Flight Aware receiver, in the tests I completed the band pass filtering and amplification out performed a standard RTL dongle by 10 to 20% range.

You will need a good 1090 MHz antenna, having something with some gain mounted as high as possible will make all the difference. I opted for a commercial made option, but if you have the equipment you could consider making a co-linear.

Have a look at the antenna options on amazon or ebay.

So having gathered all the items together, it was now just a case of positioning them in the box, the flight aware receiver has a long SMA shaft, so the hole can simply be drilled through the box and SMA pushed out. Once the SMA plug with coax is connected you can use a liberal application of silicon sealer to prevent water ingress.

I added a fan into the box, and made sure the Pi had a large heat sink fitted to the processor. The fan isn’t running right now, but this in itself provides a challenge. Not much point adding a fan if it doesn’t extract or force air into the box. I decided to drill 4 x 6 mm holes, and then as it turned out badly align these with the fan. I fitted some foam to the inside of the box, and then bolted the fan down, sandwiching the foam to the inside of the box.

Temperature readings of boxed Pi4

This again was mounted on the bottom of the box, as with every hole, to hopefully prevent water ingress. The other issue is likely to be insect infestation, they like nothing more than a warm dry home high up on a pole!

You may want to consider the application of some grease on the pole, its amazing how earwigs can find these warm homes.

Power was the final thing to do, I did try and power it direct from home, but the voltage drop was just too much. I decided to use a DC to DC converter, this allowed me to feed with anything from 3 to 16v.

PoE was considered, but i couldn’t really see the advantage over WiFi and separate power cable.

Under voltage messages would indicate I still have some issues to resolve, but its working.

The box on a pole, cable ties used as a temporary fix

Pi 4 with DC to DC converter fitted
Typical text display

Almost everything you need to go portable.

New to amateur radio, or a seasoned operator some people have never experienced the fun of operating out portable. The thrill of operating in a low noise environment.

VHF/UHF

If you going to take out your VHF/UHF handy, make sure you have a good antenna fitted. The stock antenna or the fake cheapo antenna on eBay is exactly that mostly useless. VHF operators sometimes take a vertical antenna with some gain to take advantage of an elevated location.

If your hill walking with unlicensed operators, then consider some PMR 446 radios as they provide good range and the ability to keep in touch with your fellow walkers.

HF Antennas

Speaker wire makes excellent antenna wire, lightweight and strong, and I would suggest you make a few dipoles and maybe wind them onto a former so they are easy to deploy.

If you are taking the equipment in the car, then you may want to consider getting a telescopic mast. These can be deployed behind the car with a suitable mount.

Para style cord is great for putting up guy ropes. You will also need some tent pegs to secure items in the ground. Flimsy tent pegs often bend, why not try these more robust pegs.

Guy line tensioner will come in very handy when putting up a mast.

Telescopic plastic poles used to fly flags at campsites make ideal HF antenna supports.

Power

No one wants to run out of power for their phone while out on the hills. These USB power banks will recharge your phone making sure its ready when you need it.

Everyone needs a torch, this one fits on your key ring and provides best in class illumination.

Depending on power requirements, you may wish to use a leisure battery or a suitable voltage LiPo system.  If your going QRO then a small generator will provide the power needed.

50 MHz Trophy Cup

The 50 MHz trophy cup is a great opportunity to work some stations, with lots of activity from both the UK and EU. Due to the current situation with Covid 19 this years event wasnt going to be on the same scale as previous events.

It was decided the event needed to me small scale, and to comply with the RSGB rules it needed to be a fixed station as no portable operating was allowed. Unfortunately that meant we could only put in a check log this year, as our operating site is away from home.

George M1GEO

We operated from our contest site at Kelvedon Hatch, using a 6e 50 MHz beam. The beam was located on the 12m scam mast, and the radio was the Icom 7610. 400w RF power was delivered by the Expert 1.3KFA.

Dave M0TAZ

The contest was somewhat different to usual, no portable and hence many contest stations stayed away. Conditions on Saturday was flat, with just a few SPe openings towards the end of the day. Sunday was much more interesting, with the band packed full of stations all over the EU.

QSO map for 50 MHz Trophy Cup 2020

We worked 161 stations in 21 DXCC, best DX was UY1HY @ 2288 KM

Setting up a 1090 MHz ADS-B Receiver

I have been using Flightradar24 for a while and found it very helpful in identifying local air traffic and listening to aircraft approaching and departing London City, Stansted and Heathrow.

I had for some time a Kinetics SBS-1 this was around 10 years old now, and I was looking at a more modern receiver that could link to the internet. I read that you could upload your data to Flightradar and in return, they would provide you with a business account. You can read how Flight Radar 24 collects and displays data on its website.

The best option for me was to look towards a FlightAware USB stick and to run the unit 24×7 from a Raspberry Pi. The Pie Hut even provide an SD card with Flightware already installed.

You can read more about the FlightAware USB on the RTL SDR website. The comparisons I completed with the Kinetics SBS1 and the FlightAware showed the aware was 10 to 20% better at distant reception. This could be a combination of its filtering and amplification. You can read more about the advantages and choices on the RTL website.

Raspberry Pi4 Model B

I opted to download the software and follow the instructions on the FlighRadar24 site. This take you through the options of downloading the Pi24 Image for your SD card, and then how to write that image to your SD card.

For me that all worked, up until the last stage, I setup my WiFi in the “wpa_supplicant.conf” file on the SD card and then just expect everything to work. It wasn’t quite like that, and for me I need to SSH into my PI to configure the software. Not being a regular Pi user, I needed some instructions.

The most comprehensive I could find was located here. These steps took a while to follow, but my system was never going to work without following the steps outlined. I could see from my wireless router the local IP address and port number, and worked out I could ssh by bring up a terminal window and typing

ssh pi@192.168.0.21

Or what ever IP address you PI is located. Once that was completed I needed to log into my FlightRadar24 and data started to upload the account was upgraded to business. You will need a reasonable antenna, I have described that process in this article. Coax length and antenna choice and positioning is a major issue with 1090 MHz and the associated losses.

I can now view my data in http://192.168.x.xx/dump1090/gmap.html from a machine on my network and review my statistics on the FlightRadar24 website

Example map for Dump1090
Example Stats from Flightradar24

Problems and updates

I found when looking at the local dump1090 page http://192.168.x.xx/dump1090/gmap.html I wasn’t able to display the aircraft distance. It turns out this needed to be configured, and by visiting your FR feed setting http://192.168.x.xx:8754/settings.html you may need to update the process arguments to read –lat xx.xxxx –lon yy.yyyy

FR Feed configuration screen

The next update was to the dump1090 program, this can be updated to an alternative version that includes some neat features.

TAR1090 screen

Purchase options.

External 1090 MHz antenna provides a much-improved range

The Raspberry Pi4 provides an ideal platform for your FlightAware

The Flight Aware receiver is both cheap and high performance

Cut down stock antenna

The stock antenna with the RTL dongle is too long and will require cutting down. 68 mm is the required length, and you can use some snips to reduce its size. This will improve reception, but an external antenna will provide the best results.

AOR AR-DV1 Resources

The UK is currently in lockdown, and with the government advice to “Stay indoors,” it seemed like a good time to get to know the DV1 digital scanner.

  • 100 kHz to 1300 MHz
  • FM,AM, USB,LSB,CW
  • D-STAR, DMR, C4FM
  • Alinco,dPMR, P25,Tetra
  • 3 VFO – 2000 Memory in 40 Banks

Scanning rules vary, please check local laws if in doubt.

The receiver connects to your PC via USB and requires Software to enable easy allocation of memory channels. You can search online, software ranges from free beta to expensive commercial software.

Beta Software from Wayne Taylor is available online I don’t know how long this will stay beta before going full release, so an archived copy can be found here.

DL8MRE Marcus has written some software on his site. This costs around £40, but works well and allows you to edit and search VFO with ease. The format of the native AOR memory files (CSV) is a mystery, no one seems to understand the syntax. I may have a go at decoding them sometime.

DV1 Manager by F5HPE – Free to 10EU

Online resources for finding frequencies

Scanning for Air traffic is a large part of the hobby, and so some resources can be found online.

This page will be updated as and when further resources become available.

If you have any resource suggestions, please comment and I will include them.

Thanks Dave

Talk at Thurrock Acorns Radio Club

I was invited to speak at the Thurrock Acorns club night on using online SDR radios in SWL and Amateur Radio. The idea was to introduce members to the world of online SDR radios to people who may not be aware of their usage in the hobby.

Most people have seen the great work done by the Hack Green team, but may not be aware other SDR are available that offer 0 to 30 MHz and a host of other benefits.

Over the course of the evening I described how you can view WEFAX, CW, GMDSS, FSK, NAVTEX and the new TDoA function.

The TDoA function gives amateur users of HF the ability to locate HF stations for the first time.

I put together this quick start guide to help you get the most from the online Kiwi SDR receivers.

So what have you received recently?