Dongle

[dongle]

I've hankered after doing some ADS-B decoding for about two years, but have balked at spending anything on the idea because I have too many expensive hobbies already. I've been a radio ham for about thirty years and lately have graduated towards digital modes because of local radio noise from neighbours PLT networking devices.

About a fortnight ago, I read a website article about certain TV dongles being able to be used for ADS-B decoding, so I bought one for £25 and loaded the necessary Linux driver and software. It worked right from the start, though only with limited range with a roughly made quarter wave antenna I had lashed up and placed on a downstairs windowsill.

After some experiments with antennas and lashing up a pre-amp, I am running Virtual Radar for Linux and tapping into the linux netbook over the network with a Windows PC running a Plane Plotter trial. The results are far better than I had any right to expect.

Anyone wanting to go this really cheap way into decoding ADS-B needs to realise that THE ONLY dongles that will work like this have the following chips inside them:

RTL2832 chip to do the demodulating


E4000 tuner chip to amplify the signal, tune in to 1090MHZ and output the data at base band (Direct Conversion).

The RTL2832 is quite common in cheap TV dongles, but on its own it is not enough. The E4000 tuner chip seems to cover 64mhz to 0ver 1700 mhz, and this is unusual.

These dongles have been bought up worldwide and the E4000 chip is now nolonger in production so they may not be around for long.

The antenna I settled on in the end is a simple quarter wave with eight ground planes. It is made out of 1.5mm copper wire in lengths of 67mm built onto a cheap old fashioned coax TV plug. This is mounted on the roof on a bit of cheap fishing rod, plugged into a short coax patch lead. This goes into the loft and is connected to a simple pre-amp with about 14db of gain (more or less) and then into the dongle via another short patch lead. I take the output data down into the house via a long USB2 lead into my radio cupboard where it is decoded by an Eeepc 1000HE on Linux running GNU Radio. This decodes the data into ADS-B messages. Only the Type 17 messages are used by my system.

I either use Virtual Radar's webserver to put them on the home network, or I use Plane Plotter to listen on the Eeepc's Ip address on port 30003.

My final choice of antenna so far.


An earlier experiment with four ground planes.




The setup has produced the odd few spots at about 240 miles, but more typically, I get about two hundred miles out over the North Sea and less over land where planes are obviously below the horizon in the direction of the Irish Sea where the signals have to pass over the Lake District and the Pennines. I did some looking at the terrain between my house and the Isle of Man which is my worst direction and the signals have to get over 2000 feet of Pennine Hills and 3000 feet of some Lake District mountains. It is obvious why I get the odd spot from Holland - there is nothing between us but sea.

[dongle]

Welcome to the Mob Dongle enjoy it .A great bunch of guys

                                                                                            Shaky

Welcome and thanks for sharing your experience.

It might encourage others to play with the inexpensive option. 

Thanks Shaky and Anmer.


These are the links that got me started:


http://www.ab9il.net/software-defined-radio/rtl2832-sdr.html

http://www.hamradioscience.com/the-rtl-2832u-sdr-and-ads-b/


The system worked without a pre-amp. I could get about 180 miles without one, but it works more reliably with one and I gain about another fifty miles on the occasional spot. They are very easy to make if you know which end of a soldering iron is the hot end. You needn't spend a fortune, though I am sure it is fun to do so and I have done, many times in other aspects of the radio hobby.

You can build this pre-amp for about £5.



Don't use a 6.8k resistor on the base as labelled. It is too small. The text of the article warns of this and suggests 22k. The BFP420 SMD transistor can be had on ebay at a price of two for £3.

WARNING..... Please don't connect this pre-amp directly to your dongle without putting a 100p capacitor between the output of this circuit and the dongle. If you do, you may present DC power to the input of your E4000 chip in the dongle. The circuit shown doesn't explain how to power the pre-amp, you can do like I did and take +5v off the USB supply to the dongle, but do use a dc blocking capacitor to prevent current flowing into your dongle's input. It probably has a capacitor in front of the E4000 chip, but it will also have ESD protection diodes on the input and one of them won't like the 5v positive supply one little bit.


Send me a message if you want any advice.

Instructions and photos of the simple pre-amp here:
http://www.lll.lu/~edward/edward/adsb/preamp/ADSBpremap.html

[IanH]

Mike, maybe we need to move the other dongle posts here to keep them all together?

Don't recall a "Self-assembly" topic before?

The R820T chip in newer versions of the dongle (replacing the E4000) is slowly being included in the software for SDR radio.

If you want an E4000 version:

http://www.ebay.co.uk/itm/EzTV668-USB-DVB-T-Receiver-E4000-USA-Elonics-Tuner-Realtek-RTL2832U-EzCAP-668-/150816730652?pt=UK_Computing_Other_Computing_Networking&hash=item231d60ae1c

http://www.ebay.co.uk/itm/TV301U-DVB-T-USB-Stick-DAB-DAB-FM-RTL2832U-Elonics-E4000-Receiver-RTLSDR-SDR-/150858463554?pt=UK_Computing_Other_Computing_Networking&hash=item231fdd7942

I bought the latter version from them.

Also bought a NewSky from here:

https://www.cosycave.co.uk/category.php?id_category=56

I'll be following this thread - maybe I can learn about the hardware!

Ian

[dongle]

Thanks Ian,

I have a mate who has ordered a dongle with the R820T tuner chip in it. There is confusing info around about that one and in the stuff I have seen which comes from the manufacturer, it doesn't look like it will cover 1090 mhz, but other information floating around suggests it will do with he right drivers. Those dongles can be had for under £10, whereas the Cosy Cave ones are nearly £30 now. There are some on ebay that come in at under £20 from the US with the right chipset in them.

Considering the costs and the fact that the A/D convertor is 8 bit and has a low dynamic range, the one I have is surprisingly good.

One thing I've noticed since I stuck the pre-amp in front of it is that I am not picking up planes that are taking off five miles away and flying low overhead at maybe 5000 feet. It is obvious why - their signals are overwhelming the dongle's A/D convertor. Without the pre-amp on I always spotted the local traffic taking off from Newcastle Airport as soon as they were off the ground. I have more or less direct line of sight to the runway from here. Oddly enough, when planes land, I spot them all the way down to the ground even with the pre-amp, but not when they take off for some weird reason.

[Anmer]

Mike, maybe we need to move the other dongle posts here to keep them all together?

Don't recall a "Self-assembly" topic before?

I created it last night when I saw the depth of information in "Dongle's" post.

If you can point me in the direction of the posts I'll see if I can easily move them.

[Anmer]

Thanks for a very informative description.

One question that I get asked a lot is what is used to decode the ADS-B messages and output onto port 30003?

Is it gr-air-modes?

What seems to be missing is a layman's Guide to creating the whole setup.  Clearly this isn't an out-of-the-box PC install and use option.  But maybe with a good Instruction Manual it could be?

[shakysen]

Hi All .The problem is boss there's that many folks Latched on to it  it's getting swamped at the moment. the nearest thing I've found to a user manual is on
www.atouk.com/sdrsharpQuickstart I'll keep looking



                                                                                  Billko

[Anmer]

That's the opportunity.  I'm on the case.

[dongle]

Hi Anmer,

I t certainly isn't an out of the box thing if you have no prior experience of using linux, which I really haven't although I did have a dual boot install on a netbook which I'd done just to look at what I could do with linux. However - that said, it is not really hard or anything, but it is REALLY cheap. My whole outfit, including antenna on the roof, a ten meter USB cable to the loft, software and hardware cost about forty pounds.

All I can tell you about the gr-air modes question is that I think that is a script which comes already as a part of GNU Radio which is a free download on linux. Once you have installed Ubuntu 12.04, GNU Radio, and Virtual Radar, all you need then do is plug in your dongle, connect an antenna and run an already installed script from terminal windows in UBUNTU.

[EDIT: I missed a step here. you also need to install
gr-air-modes written by Nick Foster. It is all covered in the hamradioscience link I posted. Sorry about the omission.]

I opened a terminal and typed the following:

uhd_modes.py -d -P -g 43

and within a second I had ads-b messages cascading down the screen. This was taken in the early days before I made and connected the  pre-amp. It was done with a simple little antenna - the one shown further up the thread with four ground planes. That was built on a £0.80 TV coax plug out of the inner wire from some satellite TV coax. Any self supporting wire will do of about 1.5mm, so if you don't have coax lying around, the earth wire out of some electrical cable will do. The elements should be made 68mm long if the wire is bare and 65mm long if it is covered with insulation. Just solder the ground planes to the inner cable grip and make sure there is no short between the vertical wire (which is connected to the centre of the coax plug) and the ground planes. A little bit of insulator needs to be fitted in there at the base where the cable grip will contract over the wire as you screw up the plug.

When I opened a new terminal and changed directory into the place where I had installed Virtual Radar Server for linux and typed:

mono VirtualRadar.exe

a window opened on the linux netbook which gave me details of the ip address where the server was making the Virtual Radar Server web page.



The above screen dump was snatched this morning and benefits from a small simple pre-amp I lashed up.


Since the Linux version of Virtual Radar Server tells you the network address of the web page, when in the house on the same network, I can open that on a different laptop and that way it is far more convenient since I am not tethered to the long usb lead up to the  loft where the dongle now lives with its pre-amp.

By the way - when I first set this up, I connected the dongle to the ordinary TV antenna and plugged the dongle in downstairs at the edn of a ten meter TV coax. I could see planes about thirty miles around with a horizontally polarised TV aerial set up for 800 mhz. That proved it was worth pursuing further.

This link gives as near a blow by blow set of instructions as anyone would likely need on getting the software set up and installed. It is a really good resource for anyone wanting to try this:

http://www.hamradioscience.com/the-rtl-2832u-sdr-and-ads-b/

The part underneath the heading 'Linux for Newbies' is the bit I used. It takes a while for the installs to happen, but mine worked faultlessly even if it did take a while. bear in mind, I was installing on an N240 netbook so it wasn't a power machine.

[Anmer]

Thanks.

As I mentioned earlier I'm getting more and more enquiries about this option, some from less technically experienced individuals.  But as you say, it's a cheap option and if it gets someone into the hobby that's a good start.

Has anyone tried feeding dongle data to Flightradra24.com or Planefinder.net?

[dongle]

Ah - Anmer - yes you were right. It is gr-air-modes written by Nick Foster that  decodes and makes available the data on port 30003. Apparently, it emulates the decoding behaviour of the SBS1. I completely forgot to mention that, but it is all explained in that link I posted

[dongle]

Thanks.

As I mentioned earlier I'm getting more and more enquiries about this option, some from less technically experienced individuals.  But as you say, it's a cheap option and if it gets someone into the hobby that's a good start.

Has anyone tried feeding dongle data to Flightradra24.com or Planefinder.net?

I think you will need to download and pay for Plane Plotter to be able to share your data. The dongle works with Plane Plotter, of course. You just pretend it is an SBS1 and point the program at the ip address of the Linux machine.


ShakeySen mentions SDR Sharp in the link he refers to. I tried that because there was a copy sent with my dongle. It didn't seem that great. I think there are issues about the Windows driver. Also, I am unsure how you would decode the ADS-B data that you managed to receive with SDR Sharp so you might have problems sending it to an ADS-B displaying program. Obviously, receiving bursts of ADS-B is one thing, decoding them into Type 17 messages is another. That is what gr-air-modes written by Nick Foster does for you when you type that command I mention up above:

uhd_modes.py -d -P -g 43

To me, linux is a bit of a pain, because I have never really got into it, and I can't easily remember terminal commands, but it sure as hell does this job on the cheap.

[Anmer]

I think you will need to download and pay for Plane Plotter to be able to share your data. The dongle works with Plane Plotter, of course. You just pretend it is an SBS1 and point the program at the ip address of the Linux machine.

I don't think so but it needs to be tested.

If you can get decoded data to port 30003, then the Flightradar24.com feeder software should work:

http://www.flightradar24.com/software

[dongle]

I think you will need to download and pay for Plane Plotter to be able to share your data. The dongle works with Plane Plotter, of course. You just pretend it is an SBS1 and point the program at the ip address of the Linux machine.

I don't think so but it needs to be tested.

If you can get decoded data to port 30003, then the Flightradar24.com feeder software should work:

http://www.flightradar24.com/software

Ah - well - that's good then. You can definitely do that. That is how I am running Plane Plotter. I know nothing of the Flightradar feeder software, but have data at port 30003 on the linux machine. It may be they have linux software to run on that machine, or their windows version may allow you to point at a linux machine on your network through the wifi. I have to go out now, but I will try and do that later on or tomorrow.

[Anmer]

Thanks.

There are linux feeders available:

http://forum.flightradar24.com/threads/4270-Linux-feeder-software-for-Flightradar24