FlightAware Discussions

Have i got optimum or can i improve range

At the moment i have the blue flightaware dongle and flight aware antenna plus pi3, I bought this as a kit. I only run a very short run of coax around 4m
I have a range of 256NM and the antenna is above the roof on a pole.
Do i have the max range or would i improve the range by adding maybe a uptronics filter/amp or would extra amplification overload as i already have the blue dongle.
I notice the blue dongle has amplification and filtration already.

I have the same setup (with 1m of coax) and my range and aircraft improved a lot when I added a Uputronics 1090MHz SAW filtered preamp.

In your case it’s worth adding your 40,000ft horizon to your map and seeing if you’re getting aircraft near it. Use this guide but use this URL so you can specify the correct refraction value of 0.25 (see this).

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Might get me a little more, image 1 is how i am now
Screenshot 2020-02-08 at 14.26.58.png

This one is predicted 40k

Screenshot 2020-02-08 at 14.32.19.png

I notice you have the usb coming from the pi to the uputronics box, is there enough power in the pi?
ie; voltage wise

To identify what’s maximum possible per geographic location, check it on heywhatsthat.com

Instructions how to use it are in this forum.

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Instructions are here:

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Yes indeed, I am using the official RPi 3B+ PSU which is 5.1V 2.5A. As long as your PSU meets the spec you’re good for USB power to the the preamp. You need a USB to mini-USB cable.

Is there any alternative to heywhatsit.com? It only covers to +60N, and I am north of that, so it doesn’t work for me.

I’m not aware of any other propagation tools that can handle aircraft altitudes with terrain data unfortunately . The reason heywhatsthat is limited to 60° is that was the orbital inclination of the space shuttle mission that gathered the data. The shuttle didn’t overfly areas further north or south than that.

There are probably commercially available datasets that cover higher latitudes but you would probably need to pay for access to them.

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Thanks for that explanation. Guess I’ll have to be happy with what I have now. Live in a valley, and 2 different antennas on the same mast (more than 1 wavelength) separated , each feeding its own receiver (SDR-RTL V3 and a Airspy 2) giving me exactly the exactly the same ranges and the same aircraft (plus or minus a few seconds)

     

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Have you looked at Radio Mobile?

Thanks, will look at it.

 
The plot quoted below was produced for my location (Toronto) by @G8JNJ (Martin) using Radio Mobile site.

Thanks for those instructions!

Two questions:

  1. Is it necessary to include the 0.25 refraction element to the URL if you already set that up when you originally ran the panorama?
  2. Can you re-adjust your altitude range rings at any time? I have the Uputronics LNA on the way and I may want to adjust my rings after it’s installed.

I am not sure as I never ran the panorama with refraction set to 0.25 as suggested by @chrislfa in this post.

This needs to be tested by generating panorama with 0.25, then twice running the wget command, once without &refraction=0.25 and again with &refraction=0.25 and see if there is any difference.

 

Yes. Simply issue the wget command again with the &alts=3048,12192 part at the end of command changed as required.

sudo wget -O /usr/share/dump1090-fa/html/upintheair.json "http://www.heywhatsthat.com/api/upintheair.json?id=XXXXXXXX&refraction=0.25&alts=3048,12192"

The argument -O immediately after wget results in overwriting the file upintheair.json, if it already exists.

Do NOT forget to reload your browser (Ctrl+F5) so that it uses the new file. If reload does not show new rings, clear browser cache (Ctrl+Shift+Delete) and then reload (Ctrl+F5).

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Yes, because it’s used during that URL call to perform the correct calculations, regardless of whether it was used originally when creating the panorama. A panorama ID is just a reference for a Lat, Lon and Elevation. The refraction value isn’t part of the panorama data.

There are two places where it is used – the web page that’s generated from your website interaction, and the json file that’s generated from the API call. By default both of these perform their calculations using a refraction of 0.14 which is correct for visible light, the primary function of this site. If you want to see the panorama as it is for 1 GHz radio waves then you need to specify a refraction value of 0.25.

To specify it for the website when interacting with it – eg to view rings accurately on the map, view the terrain, create an initial panorama and have it display correctly, etc – use the URL with the ?refraction=1 in it. This will turn on the Refraction box and let you override the default value by entering 0.25.

To specify it for the json file saved when interacting with the API, use the &refraction=0.25 parameter directly in the API call.

Both of these are independant and are essentially two different mechanisms for overriding the default refraction value of 0.14 (for light) behind the scenes with 0.25 (for 1 Ghz radio waves) in the calculations.

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uptronics box arrived but no improvement, i was told that as the blue dongle already had a filter and preamp that is the reason why. I did have a RTL-SDR V3 dongle so tried that instead with the uptronics and i have seen a range improvement, using the biasT on the RTL-SDR dongle.

One thing to remember about using dongles with a built-in LNA after a length of cable, they will always perform worse than having a good LNA before the cable. The cable attenuates the signal and adds noise, and amplifying the signal after the cable, both the noise and the signal gets amplified. If you have the amplifier-filter-amplifier, before the cable, the noise introduced by the cable becomes negligable. (At least some LNA’s for ADSB like Nooelec and RTL-SDR blog) follow that rule. However, if you have a powerful transmitter closeby, that might overload even the first LNA in the chain. In that situation you will need a notch filter first, followed by the LNA, etc, etc. Ideally one makes a spreadsheet calculating noise vs gain along the receiver chain. Added to that spreadsheet is also overloading factors, etc. It can become quite an involved issue knowing where to add gain or where to add the filter. A tutorial like this one, [https://www.microwaves101.com/encyclopedias/noise-figure] gives you and idea what a systems-engineer or developer has to go through. What works in one situation, doesnt mean it will be the optimum under all circumastances. There are some rule-of-thumb rules, but that is not to say it is the optimum under all circumstances.

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I suppose ideally the uptronics should be right at the antenna and then the RTL-SDR V3 right next to it, cutting the coax out all together and then running a usb cable down to the rasp pi. I would do that and waterproof it but in the even of needing maintenance, I would have to get to the top of the pole. One thing about the RTL-SDR V3 is that biasT can be switched on to supply voltage to the uptronics. I only have a ver short run of coax from the antenna to the uptronics and then thats on a back to back adapter to the RTL-SDR V3 which is plugged into the Rasp pi. Not sure whether i would gain anything or not. Certainly that set up has improved my distance a little from my previous Flightaware blue dongle only. I am at the moment assessing it over a week.