1090MHz Mode S decoder
I built an ADS-B collinear antenna using Belden Coaxial cable and connected it to an RTLSDR receiver.
Home assembly of first antenna
There is an instructional video on making a Homemade ADS-B Collinear Antenna on RTL-SDR.com
Following the video instructions I needed to cut pieces of co-axial at 114 millimeters.
This was calculated using the formula.
1090MHz at Half a wavelength.
(300 / 1090) * 0.5 or 0.138 meters.
Then needing to adjust for the velocity factor of my co-axial cable.
I found out that my Belden cable is 83%.
So 0.138 * 0.83 = 0.114 meters.
So needed to cut segments that were longer than 114mm leaving space for overlap.
Once cut I stripped each end to leave 114mm.
Then needed to join the segments. The center of one segment connects to the braid of the following segment.
Making sure that the two conductors did not short using a multimeter. Inserting a piece of insulating tape between the segments.
Once tested as not shorted, seal the join with electrical tape.
The number of segments may be variable. As each segment is 114mm long I fitted 7 segments together to be under 1 meter long.
The top end of the antenna needs terminating with a resistor. The Belden cable is 75 ohms. The closest resistor I had at hand was 47 ohms.
I purchased 1 meter of PVC pipe from Bunnings and a PVC cap for the top.
Then inserted the antenna cable and connected a feed line. The feed line was remaining Belden coaxial cable terminated with a screw in F-type connector on the far end.
I then used electrical table to bung the coaxial cable in to the PVC pipe.
Then sealed the bung and wire in.
Home assembly of second antenna
After building the above 1 meter antenna, I decided to upgrade to an antenna that is the height of my apartment.
I visited Bunnings again and purchased a 3 meter PVC pipe, tee joint, two caps and a hacksaw.
My apartment ceiling is 7 feet high. So I cut the PVC pipe to 7 feet using the hacksaw.
The old 1 meter antenna now needed extending. So I cut additional 114mm lengths of coaxial cable and joined then to form a longer antenna to better suit the new 2+ meter pipe.
Using the tee piece I connected the feed line to the side at the bottom of the pipe. The tee piece makes a firm seat on the floor for the pipe.
The feed line is bung to one side of the tee and the cap is used for the other side of the tee.
Have swapped over the RTL-SDR to an EZCap dongle and cut the feed line short to reduce signal loss.
Here is a photo of the antenna sitting nicely on the floor in the corner of my living room. It extends up to the ceiling and does not require a supporting mount.
Raspberry Pi hardware
For the initial antenna I used a Raspberry Pi 2 with an expensive NooElec RTL-SDR dongle.
The dump1090 is now running as a service in the background on a Raspberry Pi Model B. Dump1090 does not need the processing capacity of a newer model Raspberry Pi and is a good use of my older pi.
Replacement parts can be purchased for a total of $20 (antenna), $15 (rtl-sdr) and $70 (Raspberry Pi).
I successfully replaced the more expensive dongle with a cheap $10 RTLSDR dongle from ebay.
It is working well connected very close to the bottom of the antenna.
There are many versions of the dump1090 software available for download. I have tried a few of them and give details of installing an example.
My eth0 is a static address. Where XXX is your chosen host number.
Updated the operating system then install the rtl-sdr package.
I installed the dump 1090 application from Git Hub on to my Raspbian computer.
To run dump1090 after log in do the following.
Point your web browser to http://192.168.1.XXX:8080! Where XXX is your chosen host number.
The following page contains further details on how to set up the dump1090 program
as an automatically started service.
Purchase of ADS-B Antenna for work
During 2017 I also installed a copy of dump1090 on my windows desktop at work. Once again there are many available compiled versions to choose from.
I purchased a $12 DAB DVB-T USB + RTL-SDR FM Mini Digital TV Stick on ebay. This comes with a dongle, remote control, cd and mini antenna.
I purchased a $6 3dBi 1090Mhz Antenna ADS-B MCX Male Router Modem Booster DVB Tuner Digital RG174 on ebay. As this antenna was sold with an MCX connector, I detached this antenna and put it on to the DAB antenna base that has the PAL connector. The PAL connector plugs in to the RTLSDR dongle.
Shown here is the dongle and base from the DAB adapter with the antenna 1090Mhz spike at my workplace window.
Using a quality USB extension cable, the USB dongle is plugged in to Microsoft Windows.
Here are some example aircraft that I have detected.