FlightAware Discussions

Use POE to put dongle at antenna, or use an LNA at antenna

I have a few questions.

Should I use a POE setup to have the dongle and RPi close to the antenna? Or should I use the RTL-SDR ADS-B LNA/Filter, and a longer feedline to the dongle and RPi? What would give me better performance in an urban setting?

Does the official POE Hat work well in an ADS-B setup?

Thanks

50% will vote for PoE
50% will vote for LNA
:wink:

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So 50% are wrong…but which 50%?

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If I answer this question, it will start a riot.

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Nah everyone is stuck at home. Answer!

I’ve got the 1090MHz aerial on top of my ham radio aerial then a short (5.5m) of very good coax and then the LNA and everything else are mounted at the top of the mast, fed by PoE.

It’s sort of a mix of both. In an absolute ideal world, the LNA would be directly below the aerial, ahead of that short run of coax but I decided that I was prepared to accept the very small amount of loss.

It’s not quite a simplistic choice as that.
As you are in an urban area, a filter may be beneficial either way.
Similarly, an amp may be beneficial depending on your antenna, receiver and terrain.
Putting the Pi close to the antenna and running PoE is a great way to reduce RF cable losses, but the cost is the hassle of waterproofing and cooling the Pi.
Realistically, a filter/amp and good quality coax is a lot less hassle than mounting the Pi at masthead.

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It is a difficult trade off as others have already said. One other thing to consider is the potential for noise generated by the RPi/receiver combination being received by the antenna. The closer you put the RPi to the antenna the greater the chance of noise from the RPi degrading performance. There is no point in having low losses between antenna and receiver if the receiver is generating excess noise. In an ideal world with a perfectly quiet RPi you would put it as close to the antenna as possible but unfortunately the real world is a compromise.

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Just going to echo was others are saying, it depends on what the distances are for you. I have my PI 100ft in the air on POE instead of running 100ft of antenna line that in my case is not going to work. Just to add more ideas to your own mix you can also think about there is also USB extension cables which can move the radio away from the raspberry pi. I tried that personally but was not worth it for me.

What LNA are you using?

Every single piece of my system from top to bottom is documented on that link I posted. I’m using the RTL-SDR-LNA.

Yes I see that now. I have previously run a setup with the RTL-SDR LNA attached straight to the antenna. That worked well. We moved into a new house and I’m getting my setup back in place. I’m now using a J pole mount on the gable end of the roof of a 2 story house. If I use coax I’m thinking it would be 50 feet or less from the antenna to the Pi. I’m thinking that the LNA and good coax would be the better setup. Especially since snow on the roof in winter could make a POE setup unreachable if there was a problem.

My next issue is grounding. My preferred location for the coax is on the opposite side of the house from my electrical service entry. My previous setup just used a lightning arrestor connected to the electrical service ground outside the house. Not sure what to do now.

Do you need to do anything, are you in an area that suffers from electrical storms?

I live in Central Saskatchewan. We get the odd storm throughout the summer months. I know it’s a very unlikely event to take a direct hit. I’m thinking more about static buildup in summer and from blowing snow in winter. Is that a concern?

That level wouldn’t bother me at all but only know what your local conditions are like
I took a near direct strike here a few years ago and despite having huge aerials up outside, it came in through the mains power and the overhead telephone cable. In total, my insurance claim was over £10k.

Brother, if you didn’t just ask the golden question…

My answer would be whatever is most convenient for your location. I’d echo what’s already been stated as there is a tradeoff between possible noise, cooling and waterproofing or signal attenuation. I don’t think you’d see but a few plane difference either way. The most important attribute that I’ve found for any installation is antenna location. As a general rule, the higher, the better and the more free space around it, the better. In the end, simplicity generally wins out.

If your installation is indoors, don’t worry either way since you’re already heavily crippled so spend as little (in thought and funds) as possible since results will change if someone walks into the room or turns the TV on…

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Is static buildup on an outside installation generally an issue with the FlightAware 66cm antenna?

About once a year I get a power failure that glitches my SD card. I’m glad my Pi is not at the top of a mast.

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I’d vote for LNA up top, decent coax down to your man cave.
Then you can tinker with different setups side by side with the addition of an RF power divider.

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I have LNA at the antenna and a long coax cable. I prefer to keep my more expensive equipment out of heat/cold/moisture.

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