I wasn’t really satisfied with the range of reception my ADS-B receiver was getting. With the kit antenna, I was receiving signals from aircraft up to about 50 nautical miles, but more reliably only really 30 miles. That was with the antenna situated inside my patio door. I found that moving it outside increased the range but it wasn’t a practical idea to have the patio door cracked open in March. I wanted a more permanent setup with even better reception.
After a bit of research on the interwebs, I decided to build myself a homemade “co-co” – coaxial collinear – antenna. I made my antenna based on a couple of YouTube videos and this excellent description at www.balarad.net
A collinear antenna consists of a number of equal length segments of coax cable joined by alternating the center conductor of one to outer sheath of the next. The ideal length of each conductor is calculated based on the frequency to be recieved (1090 MHz) and something called the coax velocity factor. Luckily there are calculators on-line like this one at jeroen.steeman.org
The videos and other resources I found had calculated the length for each antenna segment at either 116mm or 118 mm. So after careful consideration, I decided to split the different and go with 117mm. Fortunately, I had some unused RG6 coax cable which I was able cut into the required segments.
The antenna can have as many segments as you wish, but it seems that any more than 8 doesn’t offer a great deal of improvement. So I went with 8 segments. The photo above shows how the segments are joined with the center conductor of each inserted into the sheath of the next. A piece of electrical tape not shown here is placed between the conductors. Then each connection is wrapped with more electrical tape.
After assembling all 8 segments (the last one has an F-type fitting) the whole thing is inserted into a piece of 1/2″ ABS pipe about a meter in length. The top is capped and the fitting at the bottom is wrapped with electrical tape until it fits snug.
I mounted my new antenna outside on the corner of the wall of my deck and ran a 25 foot piece of RG6 coax cable into the house to the NooElec SMArtee SDR reciever on my Raspberry Pi 4B computer.
So was it worth it? Absolutely, my reception has gone from 30-50 nautical miles to 150-200 nautical miles. At times I have been receiving signals from over 100 aircraft. That’s a big jump form the 10-15 I was getting before.
My ADSB data is being fed to the flight tracking services of ADSB Exchange. If you check their website, you will see aircraft tracked by my ground station (and many others all over the world).
Here’s a couple of screen captures that show the reception I had with the kit antenna (top) and with the new “co-co” antenna (bottom).