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Tuesday, June 23, 2015

Back with the Sats: Catching Cubes with a Dongle


I've been playing around with a little $13 DVB-T SDR Dongle receiver.  These devices normally tune 24 MHz to 1.7 GHz, but I modified the first one I had so that it would tune the HF bands.   Pete then sent me another one, which I vowed to keep unmodified, thinking that it would be fun to use it to listen to the many small Cube-Sats that are up there.  Most have downlinks (and Morse Code beacons) in the 470 MHz range.   I whipped together a simple ground-plane antenna for this band (One 6 inch copper wire as the receive element with 4 five inch groundplane elements). 

 

I then went to the "Heavens Above" website, plugged in my location, and clicked on "Amateur satellites."  This gave me a very accurate schedule of satellite passes.  I started listening. 





First I heard (and saw in the HDSDR waterfall)  the CW beacon of the Prism satellite at 7:05 am EDT today.  Prism is from the University of Tokyo and was launched from Japan.

Then Cubesat XI-V at 0711 EDT.

Cubesat XI-IV was heard at 0813 EDT.  The Cubesats are from Japan and were launched from Russia.  

ITUsPAT was heard at 1422 EDT.  The I is for "Istanbul"

Finally,  I monitored a pass of the Japanese FO-29 satellite aka JAS-2 at 1611.  Wow, this was like old times on the RS-10 and RS-12 satellites.   Lots of CW and SSB stations in the downlink passband.   Lots of fun.

At 470 MHz the Doppler shift of a low-earth orbit satellite is quite noticeable, and helps confirm that you are in fact receiving sigs from an orbiting device.

I thought it was pretty cool to take a $13 DVB-T Dongle, connect it to a small, copper-wire antenna, and use it all to receive signals from some 4"x4"x4" cubes in orbit of the Earth.

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1 comment:

  1. Bill,

    I have started doing this same thing recently.

    I find the dongles tend to be a little insensitive and easily overloaded particularily when I try to increase the gain of their onboard LNA. I have found the use of TV distribution amplifier brings my dongle to life. I have been using the Channel Master Mini 1 amplifier

    http://www.channelmaster.com/Antenna_Cable_TV_Amplifier_p/cm-3410.htm

    I don't know how well the generic $10 types would work but I suspect that their specs (i.e. noise figure, etc) are not quite a good. Of course, closer to the antenna the better but for the time being mine is located close to the dongle and it does make a real difference.

    You might also find you can easily copy the polar orbiting weather satellites with your dongle NOAA19, 18, and 15 are the currently operating ones and software such as wxtoimg makes it easy to turn recordings into images. Of course you could also use a virtual audio cable and pipe audio from your SDR application directly into wxtoimg. A simple antenna for 137mhz and the above or similar amplifier could get you going very easily.

    here is a link to some I have recently copied:

    https://www.dropbox.com/sh/x45p5mh44196tke/AADHedh7SBm7ZmP_32F3GOM_a?dl=0


    cheers, Graham ve3gtc

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