FlightAware Discussions

978 Kills 1090

So, today I successfully added UAT978 to my RPI setup and I have to say I’m very disappointed. First of all, I had a little fan blowing on the SDR dongles to keep them cool - big mistake. See below. Lots of interference from the fan noise. But when I successfully added 978 to my setup, I lost a TON of range from my 1090 setup. You can see the pictures I’ve attached. Turning off the fan certainly decreased the noise. But it wasn’t until I stopped dump978-fa that I really gained back my 1090 data. I don’t know what was happening, but I can say that the second I killed the dump978-fa process, my reception went through the roof (at least back to where it was before adding dump978-fa).

I killed the fan at about 14:20
I stopped dump978-fa at about 16:10

Thoughts? Although killing my fan decreased radio noise, it seems that the bigger effect was stopping the dump978-fa process entirely.



Do you have separate antennas for 1090 vs 978? The rtlsdr dongles are noisy and will interfere with each other if you have them connected to a single antenna without good isolation. (Also, USB can be noisy depending on exactly how you have things cabled - try rearranging cabling)

Running two dongles on one Pi tends to expose problems with power or USB bandwidth. Do you have a good power supply? Is there anything else using USB?

Also a core temperature of close to 80C is hot for a Pi, it will probably be throttling at that point, you may just need more cooling. The dongles do dump quite a lot of heat which is especially a problem if you have two connected.


So just to clear up any confusion of other people not as familiar with radio, it’s not the literal noise but rather EM noise.
I’m sure the amount of radio noise emitted by fans depends heavily on the model.

Secondly the causality can also be another one.
As mentioned if you are power / voltage bottle necked then that can be worsened by a fan if it’s connected to the same power supply.

Your ADS-B range is very bad even standalone so the setup could use some improvement anyhow.
If you want some hints make a picture of the antenna and its surroundings and a picture of the pi and some people here might be able to offer some pointers.

First thing i’d focus on is power.
Which model pi is it and which power supply?

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That range really isn’t good(as @wiedehopf stated above). I was seeing that kind of range when I used an antenna on my basement window guards, maybe 2ft/0.6m off the ground (house is only 20ft/6m AMSL).
You may want to look at optimisng the gain(Plenty of posts about that on this forum).
If EM noise is an issue, then possibly metal cases for the dongles(soild out at the moment), unless you already have them or short 6"/15cm quality USB cables to move the devices a little further away from the RPI. Some sort of filter may also help. In my location I have to use cavity filters because I have way too much EM noise (A half dozen Cell towers within a few blocks of my house).

I have one setup, in my bedroom, that loses a lot of range when the TV is on, even with a cavity filter.

You could also try using different USB ports (if it is an RPI4).

Thanks obj,

Separate dongles and separate antennas. The CPU temp was only temporary. The peak you see is when I disconnected the fan… temp spiked, but when I disconnected the 978 dongle and stopped the process, the temps went back to 55-65. It sits on in a window right now with a west exposure (west chicago suburbs) so as the sun shines on it the temp is rising.

I’m using the Raspberry Pi power supply for my Pi3b.

These are the dongles I have:



Yeah… I have range issues. I’ve seen lots of posts about optimizing the gain. I’ll have to look into that. The first day I set up my Pi with 1090 last week, I was pretty happy. I was seeing aircraft out to 160mi.

Then I started the process of adding dump978-fa. I can’t say with certainty that this is what caused my range decrease, but this was 2 days ago:

So, I pulled the dongle and stopped the dump978-fa service and now it’s like this (last 24 hours):

Believe it or not, that’s actually much better than things were two days ago. Lots more airplanes are in the 40-80 mile band because that captures lots more ORD traffic for me.

Your main issue are the antennas, having them so close together is what reduced the performance.
Also the fan wouldn’t be an issue if it wasn’t directly next to the antenna.

Well could also be that it’s feeding back through the 5V rail because the SDRs aren’t great.

Build yourself some quarter wave antennas that can be place at least a foot apart and a foot above the pi.
QUICK SPIDER - No Soldering, No Connector

You can just make it a bit longer for 978 but it’s not that critical anyhow with this type of antenna.
Would improve your reception a lot.

What is your fly-screen made of? (is it metal?)

Without moving anything else, can you open the screen to see if there is any change?

Some ferrite beads on the fan leads might help. Also, use a dunny roll core as an air-duct to get the fan further away from the radios.


For those not from Australia or New Zealand

Dunny roll


Thanks SweetPea - I chuckled when I read that. I was able to translate only because I had the same thought. But I’m going to use an “American Sized” Dunny Roll :slight_smile:

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Thanks- when I saw how those pictures came out, I pulled the screen off to test. It really didn’t make much of a difference - I don’t believe it’s a metal screen. I had ordered this antenna and added it to my setup last night and it seemed to made a big difference. I’ll probably have to wait for Monday to see a lot of traffic and see what range I have.

Eventually, I’d like to mount this outside but I’ll have to find a sneaky place that my Homeowners Association won’t notice.

Any thoughts on Gain? I know there’s a ton of info on adjusting it for better results, but I thought I’d ask here. Thanks.


Couple of suggestions.
The aluminium between the glass planes is very close to your new antenna and may be degrading performance.

The big antenna may be putting a lot of load on your connectors and may break one if it falls over.
Try tying a string to the top of the antenna and hanging it in the middle of the window