I recently started to play with my SDR (Software Defined Radio) trying to receive any radio signal I could reach and decoding them. Due software limitation on Mac OS X, I'm currently focusing on NOAA weather satellite imagery and ADS-B (air traffic surveillance).
When at home, I can receive some signal from NOAA 15, 18 and 19 indoor but it would be rather weak, unless the satellites are passing high overhead. My other option to get a strong signal is to climb on the roof of the house but as I'm surrounded with mountains and trees, I need to wait until the satellite is at a certain height above the horizon before I could get something.
Today, I decided to drive to Terrigal "The Skillion", about 30 minutes from home. The Skillion is a cliff at Terrigal. It's approximately 100-150m high and it's wide open all around which is great for capturing radio signals where line of sight is important.
First task is to climb up to the top:
NOAA 18 Weather Image
After I got up there, I first setup my antenna for NOAA imagery. From memory, each of the antenna element is at about 16.51 cm forming a V shape at 120 degrees pointing South and the radio is tuned at 137.9125 MHz.
I then connected the antenna to a RTL-SDR v3 USB dongle itself connected to a Macbook Pro running CubicSDR for receiving the radio signal and Wxtoimg for decoding it and generating the weather image.
I'm using the Orbit a free iPhone app for tracking satellites. It shows the satellite and its trajectory in real time and with the iPhone's compass it's easy to track the satellites.
For a better signal, I could hand hold the antenna and point it at the satellite but NOAA satellites' trajectory are always North-South so a 120 degree V-Dipole antenna pointing North or South is enough to receive a clear signal even when the satellite is low on the horizon. I was impressed as I usually needed to wait for the satellite to be high enough but this time I could get a signal even before the app is telling me that the Satellite is at the horizon and I could still get it after it has disappeared from the app.
As the computer was recording and displaying the raw image in real time, I walked around and enjoyed the view from the top of the cliff.
And here are the final result. The image on the left is the satellite image with a map overlay. The one on the right is with precipitation data. My computer receives the image starting from the bottom. At the beginning there are some noise which is why you can see those black bands. As the signal gets clearer so is the image.
ADS-B or tracking aircraft using a radio device.
With my SDR, I can also receive ADS-B signal from aircrafts navigation system sent via RF on the 1090 MHz frequency.
Before leaving for Terrigal, I tested the system at home to see what I could get and here is the usual result when indoor with the antenna on a suction cup on the South window. I usually get aircrafts up to 200 Km away from my place and then they disappear.
Today at The Skillion, after playing with NOAA 18, I re-setup the Antenna for the 1090 MHz frequency by switching it to 7cm elements vertical dipole. Tracking from the cliff improved the signal reception quite noticeably, as soon as I launched the app (modesdeco2) it instantly showed some activity.
And after a short while, I managed to get 13-16 aircrafts on display:
For the first time, I was able to track aircrafts more than 200km away. One of them was over 300 km away. I should come and try again during the day when there is more traffic.
Here is a list of some of the flights that I managed to track:
And here are some stats from the modesdeco2:
It was good fun out at The Skillion at night which I've never done before. I'm looking forward to my next attempt, maybe with a better antenna that I would build myself.
Previously on my blog:
- Tracking airplane flights with ADS-B and no Internet using dump1090
- Entering the world of RF (radio frequency) with weather satellite imagery
- Gravity Meditation or free your mind doing Rock Balancing
- A walk in the bush with a Nikon P7100 camera.
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Credits
- The image at the top has been generated with the Canva app using my own photo.
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