Rotary dipole

I once got several of them for 40, 20 and 10m and wanted to see how they perform and whether you can put them easily up in a mobile mast.

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This is the basic idea, 12 meter aluminum, a short tuned dipole in the mast and start DX’ing. Big question is, can the mast hold it? It did with wind up to 3 to 4 bft 
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Caught the interest of a red rooster
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Base for the mast
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For safety I added three guy wires, and I used a light rg58-u cable to the dipole.

Last update: 15-May-2019

Feeding your ADSB data to websites

Why do you want to do this? Because more receivers on a map see more than one.

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Once you are convinced that you got a reasonably working antenna that is also protected with a lighting arrestor (for availability see for instance this shop), and where the mast is also grounded (this guy describes it, I did something similar) you can set-up a feed to one of the websites that continuously run a virtual radar or a flight tracker. I have currently setup a feed to flightradar24 and adsbexchange as I wrote earlier.

There are several ways on how to accomplish this, but it is fairly well described on a number of websites. I already had an unused airspy SDR and a raspberry pi basically doing nothing, so this is what you want to use.  The steps to get everything running with an airspy and a raspberry pi are:

  • Update the firmware of the airspy, it is described here
  • Get the airspy to behave like a spyserver, it is described here
  • Test this with sdr# which should show that a spyserver is there, this means that you got something to work (for adsb you don’t need the spyserver, but if you have the airspy you probably already had sdr# and it allows you to check whether the network connection to the airspy is reliable).
  • Next setup a virtual radar client in a browser so that the remote airspy on your raspberry pi should become visible.
  • Get the adsb software from adsb exchange
  • Complete all installation procedures from the previous step, in the end you should have running, airspy_adsb, socat, fr24feed, and mlat_client on the raspberry pi.
  • By now you should become visible on the website of flightradar24 and also adsbexchange. On the flightradar24 website you should get reports of what you are feeding plus that you get a free business account as a thank you for feeding the receiver data. I’m not affiliated to any of them, except that I have an account.

Running MLAT is more than showing only the GPS positions and velocities transmitted by aircrafts which is what the virtual radar tool shows in a local browser. Reason is that  MLAT will try to guess the position speed and height of an aircraft only from the receiver aircraft transponder data without the support of GPS. Many aircrafts don’t have a GPS system, so you have to use tricks like trilateration to guess where it is, much like fox hunting in hamradio. So MLAT is using the information from several receivers, the more the better. In the end simply let it run, and check how you perform on the one of the mentioned websites.

Last update: 8-May-2019 12:45 (Added some clarification etc)

ADSB antenna

My latest verdict on the best performing ADSB antenna, the collinear is the winner.

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Zooming in on the latest ADSB antenna, it is a 8 element version as described before, it is 12 meter above the terrain
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ADSB coverage plot as obtained today.

The antenna field of view is obstructed mostly by trees and buildings, but you can see aircrafts up to 300 km away.

Update: currently I’m running ADSB setup on the airspy and a raspberry pi3, it is feeding flightradar24 and adsbexchange continuously. I will report on this later in a new blog article.

Last update: 8-May-2019 7:00