FlightAware Discussions

Tracking both overhead and distant aircraft

I have been using PiAware with a Pro Stick Plus and this antenna https://www.amazon.com/Bingfu-100MHz-1800MHz-Magnetic-Compatible-Software/dp/B07HQJKMBD for a few years. The antenna and the Raspberry PI have been in my attic and I have gotten reasonable coverage out to about 50-60 nm. Recently I built a simple dipole antenna which I installed in the attic and moved the RPi down to the house, connecting them with RG6 coax and an amplifier. Now I can see aircraft out to 100 nm, but anything within about 5 nm is invisible. Because I live in a suburban area between two busy airports being able to see nearby traffic is very important to me, but I would also like to increase my coverage.

I tried connecting both antennas through a combiner, but it doesn’t work very well and upon thinking about it, there’s no way that it should. After doing a fair amount of research on this forum and other places to find an antenna that might work for me, it seems like there’s an inherent tradeoff between having an antenna that can see distant aircraft and one that can see ones right on top of you. You can’t have both. Designs like a dipole or collinear seem to have a lot of range and the monopole is great for seeing aircraft overhead especially if it doesn’t have a ground plane.

As an alternative I am thinking of getting a second ProStick Plus so that I can connect an antenna to each one and then merge the outputs of two instances of dump1090 running on the RPi. This would seem to be relatively straightforward and appeals to me more than spending time building DIY antennas since I have a lot more experience with software than RF. I would be interested to hear anybody’s thoughts or suggestions.

I would definitely try reducing gain first. There is a thread here called “Thoughts on optimizing gain” (sorry i don’t have a link handy) that has a lot of good information in it.

The net of it is most likely that you had to have your gain set very high for the old antenna to get any results, and now with the new one being more sensitive, any nearby aircraft are overloading your receiver.

Thanks, I had not seen that thread. There is another one that discusses adjusting the gain, but it seemed to be relevant to different hardware than I have.

Here’s the link. Sorry for being lazy earlier: Thoughts on optimizing gain

Seems too much gain (LNA in ProStick Plus and and an additional amplifier)

Can you give some more details:

  • Is the amplifier near antenna or near the RPi / Pro Stick Plus
  • Details of Amplifier
  • Length of RG6 coax

@abcd567 - It’s an inline satellite amplifier that I had laying around. 950-2250 MHz, 16-20dB sloped gain. It’s right next to the antenna and powered through the coax. I don’t know the exact length of the RG6, maybe 50 ft.

@jafrank - My gain was set to -10 which was the default setting and apparently means it’s set to automatic. The percentage of strong messages was 74%. I changed the gain to 40 and now the percentage is around 5% and I’m not seeing the nearby aircraft disappearing. Currently I have the old antenna connected so I’ll climb up into the attic later today and switch to the dipole.

Oh, what a coincidence!
A diy dipole, satellite amplifier 950~2050 MHZ, 50 ft. RG6 coax, diy bias-t was my first setup when I started this hobby in 2013.

However as FA Pro Stick did not exist at that time, I used a 2nd satellite amplifier down the coax line and a Generic DVB-T plugged into Windows PC (I did not have a Pi either). I could get a range of 450 km (243 nm).

After few months I discovered that the 2nd amplifier has a negative effect on nearby planes (too much gain), and removed it.

As you cannot remove built-in amplifier of ProStick Plus, reduce gain setting of dongle. Do not remove the satellite amplifier near the dipole, as 50 ft. of RG6 coax will reduce signal from distance aircraft below noise floor, and your rang will drop considerably.

Try different value of gain settings like below, and at each setting observe for some time. You will finally know where you get the best results.

49.6, 45, 40, 35, 30

If you are using Piaware SD card image, reduce gain by following command:
NOTE: replace xx by the desired gain number

sudo piaware-config rtlsdr-gain xx  

sudo systemctl restart piaware  

If you are using Raspbian image with piaware package install, edit dump1090-fa config file as follows:

sudo nano /etc/default/dump1090-fa

In this file scroll to following line, and in the part --gain -10, replace -10 by desired value of gain.

RECEIVER_OPTIONS="--device-index 0 --gain -10 --ppm 0"

Do not forget to remove minus (-) sign which is just before the number 10. If you use any number with a minus sign (except -10, which is a special case), it will set gain to ZERO and you will not see any aircraft on your map.

Save file (Ctrl+O) and close (Ctrl+x)

Restart dump1090-fa
sudo systemctl restart dump1090-fa

That worked. I have the dipole in the attic connected through the amplifier and after some playing around with different values I have settled on a value of 28 for the gain. I’m seeing aircraft directly overhead at 3000 AGL as well as aircraft as far out as 100 nm at FL 400. I don’t think I can do any better than that with this setup. I’m eventually going to mount an antenna on a mast on the roof which should make it better. I doubt that I’ll be able to get a lot more range in some directions though, because of nearby terrain.

Thanks for the help.

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Oops, I spoke too soon. I’m seeing the departing jet traffic overhead, but there have been a couple of low helicopters today that were not detected until they were a mile or so away. I decreased the gain and that seems to have made them reappear, but I have lost some range on the distant ones.

I started looking into adding 978-UAT capability since I am within 10 miles of four GA airports. It looks like that works the same way I was considering fixing my problem earlier, that is by using multiple Pro Sticks whose outputs are combined in software. So I could have an antenna and receiver that is optimized for distant 1090 traffic, another one for near 1090 traffic, and a third for 978.

I was in a similar situation - two major airports (labeled “International”) in a few miles radius from me.
Major air traffic lanes right overhead and others 100-120 miles away - I wanted all of them.

I have switched to Airspy dongles because of their better dynamic range (12 bit ADC with 10.4 EONB).

But we’re in diminishing returns domain… it depends if the $99 (mini) or $169 (R2) means a lot for you or not. And you need a filtered LNC for those, they don’t have one inside like the FA ones.

PS: To understand what I am talking about, this is an example of my tracks:

Ahh - dynamic range - that’s what is lacking. So if I improve the antenna it’s going to produce a stronger signal which means I’ll just have to turn down the gain more and nothing will change. I’m not serious enough about this to spend that much money on a new dongle, so I think I’ll stick with what I have. Other than the novelty of seeing a plane that’s 100 miles away, I’m definitely more interested in the local traffic.

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Not completely.
Close by aircraft are on average higher over the horizon than aircraft far away.

So building an antenna that has more gain on the horizon (basically all high gain antennas) then you can increase your gain on the horizon more than the gain at say 20 degrees above the horizon.

If the local flights are low (helicopters), they will appear at low angles too. That’s what bothered him a few posts back. But yes, it’s a hobby, nothing to gain per se, but having fun and relaxing.

That’s a good thing to consider, but I don’t think that would help. A helicopter that is 1.25 miles away at 500 feet is at the same angle above the horizon (4.33 degrees) as an airliner that is 100 miles away at 40000 feet. Also I am surrounded by mountains so anything far away that closer to the horizon is going to be blocked.

And they are so weak you lose stuff at 100 miles?
Even when optimizing for close in reception i’d expect 150 nmi range unless terrain is in the way.
I suppose with trees all bets are off.

Two antennas two dongles two receiver

For nearby aircraft:
Antenna 1, low gain (1/4 wave dipole or ground-plane) >> dongle 1 set at low gain >> dump1090-fa-1 >> map 1

For faraway aircraft:
Antenna 2, high gain (Flightaware or Jetvision) >> dongle 2 set at medium or high gain >> dump1090-fa-2 >> map 2

The twin setup can be done either in two RPi’s, or in single RPi running two independent instances of dump1090-fa and piaware.

 

good post with the antenna patterns. I was aware of what you are showing but was unable to come up with a decent drawing. The overhead donut hole is evident on my DPD antenna.(DPD was the only commercial antenna available with any gain when I bought it) I had decided to just continue on with that antenna and trade off that for range.
If my memory is correct a discone perhaps has the best overhead performance; but check me out on that statement

The overhead planes are at max 10km away. No need of higher gain antennas.

Exactly.
Even a mag-mount whip on a window sill is sufficient to cover up to 30 nm with Generic DVB-T (no internal or external filter or amplifier)

That’s a lot of great information, @abcd567. I had previously only heard vague descriptions of the differences among the radiation patterns of the various antenna designs. The graphic is very helpful.

Your Github project is also very useful. That shows me that I can easily do what I was thinking of. I would want to do it a bit differently, though. I would want only one instance of piaware that is reading the merged outputs of two (or more) instances of dump1090. A program to do that is very easy, but I was not aware of the data going in the other direction from piaware to dump1090. I need to dig into this some more.