FlightAware Discussions

Building a new receiver, this is going in a prime location - Suggestions for receiver/preamp/filter please

hello keith, regarding the 3B+, are you currently using the auto gain script on this site, and if so do you have the airspy graphs?

I do have the gain set to auto - Due to the fact it’s behind a cgnat, the graphs and map are hosted from another Pi and so that info isn’t passed over. Which graph(s) are you interested in?

The CPU graph you’re seeing is the CPU on the Pi that’s doing the hosting, not the actual Pi that’s at site. I have the CPU limited to 85% by -C and the preamble filter is limited by -E to 6. Any more than that and I get many, many lost samples.

I access the Pi itself via VNC and as soon as I do anything on it, I also get lost samples, it’s running that close to the limit.

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It might be worth installing zerotier on that pi. It creates a virtual network which would allow you to ssh in without having to use vnc and it works fine behind cgnat.


the “Airspy MISC” graph that shows the variation of gain. i also have a 3B+ (maybe santa will bring a 4) and would like to see how your gain varies over a 24 hour period if available.

My Airspy is getting up to 1800 with a traffic of around 100 aircraft. So it’s pretty normal that the airspy is getting higher with more aircraft.

I have it installed on my devices after beeing a bit sceptical. But it works perfect

It would definitely be both more bandwidth and cpu efficient for a remote site than VNC.

@keithma @foxhunter cool you both using an Airspy? Which model and which decoder software?

Did you really noticed a diff between a blue FA stick or NooElec Smartee v2?

Here you go - It’s not very exciting.

Thanks - I’ll take a look. For the normal stuff, I’d much rather get in via SSH. It will still have VNC on it because I’ll need to access the GUI sometimes to look at the graphs locally which aren’t pushed over. But for normal day to day use, I’m much happier via SSH.

I second that. Very easy to setup, not a lot of extra load, and stable.

Just done it on the Pi3 at the MTG - Very good, seems to work well.

Thanks folks, that’s a really good call.

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Airspy mini - readsb by wiedehopf together with the latest driver he provided


I read a lot before i installed it.

Now i have Zerotier installed on my Raspberry and on my local Notebook. I do have full access via Zerotier, even if i am not in my home network. No need to open ports etc, only clients you have configured as Zerotier clients can access each other.

You can for example limit SSH access to the network you have set up via Zerotier. No other client can access it then.

The only disadvantage: You have to install a piece of software doing that. If you’re not allowed (e.g. my office device is blocked installing apps) then it becomes difficult

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I used ZeroTier to access my sites in US when I traveled in Europe with no issues. Even reboots worked OK. That might be dicey if something newly installed/upgraded locks up.
I have ZeroTier on Android phone, Kindle Fire tablet…

PS: Installing on work devices? On my work laptop I am not allowed to even plug in my phone in USB to charge. It will lock-up.

I won’t be installing it on any work equipment. I’ve put it on the MTG Pi plus installed the client on both my iMac and M1 MBA. It’s working perfectly. That was a good tip, thanks.


That is still possible for us. We do have work USB-Sticks and cannot disable that. However I cannot install or even launch software which wasn’t installed using SCCM

But i can live with that. Work is work, i don’t need access to my devices from there.

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OT: We have too USB HDDs. But their serials are registered and “authorized”, and they are fully encrypted. If a un-authorized device is connected, the laptop locks up. Some of the new hires don’t pay attention to the orientation and find that the hard way when they plug in their smart phones. I always asked myself “who does that?”.
Heck even the optical drive writing is disabled on most of our laptops, have to use an approved web-storage service.

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Pi was delivered today, it’s all built.

Raspbian lite

VNC set up along with ZeroTier One. All I need is for my friend Tony to do the actual swap and then I can install mirror-json (because it’s behind a 4G cgnat and has limited bandwidth) so the graphs and map can be pushed to the remote host Pi and then change the feeder number.


The Pi4 was installed today and after some help from @wiedehopf, I’ve got the graphs and map updating.

It’s currently configured like this:

gain= auto
OPTIONS= -v -f 1 -C 90 -e 2 -w 5 -t 300 -P 10
sample rate= 20

Because it’s the time of day when aircraft numbers are dropping, it’s really difficult to see what difference it’s going to make so I’ll be closely monitoring it over the next few days.

The Pi4 isn’t overclocked. Pictures to follow.


Nice job!

I can remember once i moved from Pi3 to a Pi4 it gave me an improvement of about 5%
But without measuring properly it was more a wish to come true

Why is the Airspy SNR wider?

And it looks like the range has been increased a bit.

I don’t know - Possibly due to the increase from 12MHz to 20MHz? The gain has gone up and the preamble filter has increased as well.

I think so - The last few days have seen range increases in the evening so it’s difficult to tell. It does have slightly better coverage out to the west than my main receiver.

I think this site has more potential too, I reckon I can get it another 15ft higher.

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