ADS-B In-line amplifier experiments and bias T for 1 Ghz

By Easter was in Portugal and got an in-line satellite amplifier since it covers the ADS-B frequency of 1090Mhz

The idea was to put it in service for the ADS-B receiver, improving reception

Without any proper quality equipment to verify the effectiveness, decide do use the QSpectrum analiser software and record the data for comparative analyses.
In the process also trimmed the antenna to different lengths...

ending up in around 7cm (6.8 should be the calculated exact size).

Testing was done inside so subject to nearby interferences and yes, the support is a broom stick...

Here's the experiment and results:
 Testing with just the cable, no power and the amplifier inline:

 Powering the amplifier and no antenna:

Amplifier on without antenna and smoothing 100nF cap on the power line to the amplifier:
 
 Here with 1pF as DC blocking capacitor on the bias T:

 Now, opening the balcony door on the living room (where I was experimenting) changed results:

 Now still with the open door and a 10pF cap blocking DC:

I closed the door and experimented with a 120pF capacitor:


Testing the antenna ground plane:
7cm with GP:
 

7cm no grGP:


Ground plane helps :)

Different antenna sizes:
14cm


13cm

12cm

8cm (different scale since approaching the expected length)

7cm


In the final configuration it improved reception from my previous experiences, still the antenna being in house only get's a max of 60miles/100Km coverage.

The bias T for the amp ended up as a simple 180pF dc blocking capacitor (C1) one RF choke and a smoothing capacitor. The value was selected as a low capacitive reactance at 1Ghz and a little higher at lower frequencies:

@ 1000 Mhz

    1 pF - 159    Ohm
100 pF -     1.59 Ohm
180 pf -      0.88 Ohm
100 nF -         1.59 E-3 Ohm

@ 100 Mhz

100 nF - 1.59 E-2 Ohm
180 pF - 8.8 Ohm

The implementation and schematic:

Only missing now is to enclose everything and place it on the roof.

Have fun!

ADSB + ACARS with SDR dongle on Linux

In 2013 I got one of those SDR dongles, Idea was for RF spectrum view and a standalone SDR receiver.
Well I tested it for some reception and it works ok for the price of it. Haven't used to much recently but in any case leaving here some details how to get ADSB and ACARS decoding if you use Linux, i've run it on two different Linux Mint distributions although the guide is more geared to Ubuntu.

The dongle with the test antenna (the classic piece of wire):

The complete instruction for ADSB I got from this site:
 ( http://landoflinux.com/linux_sdr_adsb_gqrx_radio.html)
There is also a version with MySQL support for historical logging at: 
 http://lee.smallbone.com/2014/03/ads-b_via_dvb-t/

After compile you can run the webserver with the display of planes using the following command:

# ./dump1090 --enable-agc --aggressive --net --net-http-port 8080

Point your browser to http://localhost:8080 and you should have a similar view to this:

and another along side with terminal for monitoring:

If you need to check if listening on port 8080 execute the following:

# netstat -ln | grep 8080

... output should be similar to this: 

tcp        0      0 0.0.0.0:8080            0.0.0.0:*               LISTEN

If nothing returns then it's not listening....take in account that some proxy's software generally use port 8080, so look for another free if that's your case.

Running the command without options you just get the scrolling output of the frames received:

 For ACARS reception, follow this guide.
(http://www.satsignal.eu/raspberry-pi/acars-decoder.html)

And run the following command (you can include just your area ACARS frequencies):

#./acarsdec -p 0 -r 0 131.525 131.550 131.725 131.825

If you look on the guide (on the link) there's a way of including frequency correction, I considered 0 just for testing and still got some outputs with the piece of wire antenna inside house:

...I'm positive I've flew in the the EI-DES from AerLingus before.

Have a nice week!