Hey all, been running PiAware on a Pi4 for about two months with the FlightAware 1090 antenna in a 3rd story window. I’m getting ok reception with about 1200 aircraft a day with a handful at 100 - 150 miles. I’m looking for a good way to improve reception.
I buried a coax & ran to a pole in the backyard for a cable tv/internet connection about 50 ft. from my house that is no longer in use. I’m a coax newbie and cannot identify the type of cable or connectors I would need to accomplish this…my plan would be to use the existing buried coax, attach my antenna to that on the pole in the backyard and the other end already in my basement to my Pro Stick / Pi4.
Here are my questions:
Can anyone identify the coax in this picture?
Will it be suitable for use with the antenna I have (FlightAware 1090)
What size connector is on the coax and what do I need to attach it to my ProStick / SMA on the antenna?
I could just run 50-60 feet of new LMR400 in a fitted length… is that to much distance to receive signals?
It’s likely a 75 Ohm coax if it’s for TV/cable modem. This is not ideal since the rtl-sdr stick should be 50 Ohm, but it will work with a slight loss due to impedance mismatch. Running a new 50 Ohm coax is the ‘correct’ thing to do, but you could get away with using the existing one if you are prepared to endure the disapproval of the purists and you don’t mind the slight performance loss.
You have a prostick which has an LNA built in, which is OK for a short length when the dongle is relatively close to the antenna, but it’s not the best for a long cable run. Ideally you’d have the LNA placed as close to the antenna as possible so the coax comes after it. This will make a big difference to signal to noise ratio, as with the amplifier at the receiver end of the chain, it will amplify all the noise induced by the coax. If the amplifier is before the coax, the induced noise remains small relative to the signal. You might find a filter is necessary depending on your local conditions.
The other issue to consider is height - does the pole in your back yard give enough height to get the antenna above any local obstructions and buildings? If it does, that’s good since it should give a clear view of the horizon, but if not then you might not get as much improvement over your current position as expected.
The connector on the prostick is an SMA. You can get adapters from SMA to F connectors which will fit the existing cable. The Flightaware antenna has an N connector socket. Again, adapters are available from N connector to F connector. That would be the cheapest way to test it out.
If you run a new cable, you can just buy the appropriate plugs to fit it. The SMA is quite small for putting on the end of LMR-400 however so using a short pigtail for flexibility might be a good idea.
Coax cable is either 50 ohm or 75 ohm impedance. TV cables like your orange cable is 75 ohms and the Flight Aware antenna and receiver dongles are set up for 50 ohms. This causes a small signal loss at each connector and transition between impedance types. The connector on your orange TV cable is called a F type connector.
The connections will look like this: FA antenna >> a Male N to female F connector >> Your orange cable >> female F connector to Male SMA connector >> Your ProStick receiver.
The orange TV coax has higher losses at the 1090 MHz / ADS-B frequencies. One option to use an Low Noise Amplifier (LNA) just below the antenna Male N to female F connector to amplify the received signals and overcome losses of the connectors and lossy cables. The LNA would likely have to be in some kind of waterproof box, Since the LNA needs some power, you may want a Bias-T adapter next to the ProStick receiver to inject some DC power to go up the cable and connectors to power the LNA.
Other responders will likely chime in here and add their thoughts, likely more useful than mine. This is a hobby where we all make changes to our systems to get the best performance, and usually made as small improvements over time. Have fun learning how it all works and definitely install the GRAPH1090 software so you can evaluate how your changes. Best wishes1
[XRDS -RF KMR400 SMA to N Cable 75ft, N-Male to SMA-Male Connector Low Loss Extension Cable 50 Ohm SMA CableXRDS -RF KMR400 SMA to N Cable 75ft, N-Male to SMA-Male Connector Low Loss Extension Cable 50 Ohm SMA Cable]
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Nice coax find. It should keep your raspberry pi quite happy. You will likely receive from a much wider area than the antenna in the window. Antennas work best generally as high as possible, and clear of obstructions. I do believe your new configuration will increase the planes & messages you receive. Nice solution and much easier to implement than my first answer. Definitely having some fun there!
Thanks all, I really appreciate the guidance. I’m going with the new 50 ohm cable and at least the old cable is already in a conduit that I can just pull the new one through. Thanks also for the GRAPH1090 point, hopefully I’ll report back with a greatly increased reception next week!
