Improving overall performance


#1

I tinker with the hardware setup here, much more than the software aspects. Even with the Dump1090 code available, software development on the Pi is not much fun.

The old operational system was mounted in a outside wood shed. It had a FlightAware 26 inch antenna, 1 meter quality cable N to SMA male, FlightAware ProStickPlus, Raspberry PI. The operation of this system was very sensitive to how the cable from the antenna to the RTLSDR dongle was positioned. My location has a large mountain just to the east, significantly stopping all eastern traffic. The highest message rates were about 360 per second and 70/50 planes detected/positioned. With the best cable positions, the system detected between 1800 and 2000 unique planes a day with a range of about 200 NM. Range here is limited by the terrain and mountains. The microSD is a standard class 10 that came with a kit.

I set up a separate microSD card to run a spectrum analysis and even with the filter in the ProStickPlus, I could see strong interference both above and below 1090 MHz. The strongest signals were at 860 to 900 MHz. They were stronger than 1090 MHz and probably affecting the performance of the system. Searching I found a interesting filter. https://shop.jetvision.de/epages/64807909.sf/en_GB/?ObjectPath=/Shops/64807909/Products/71010 The delivery time was about 30 days from Germany.

The new operational system is really the only one that counts. Here is the configuration: FlightAware 26 inch antenna on a pole about 18 ft above ground next to the shed, 25 ft of quality cable N to SMA male, the above Jetvision.de 1090 MHz 3 Pole Filter (SMA Female connectors), 5 inch SMA male to SMA male, FlightAware ProStickPlus, Raspberry PI.

Installation was fairly simple, wire up the antenna, attach the pole to the shed, get the cable into the shed, connect cable to the 3 pole filter, then connect the filter output to the ProStickPlus.

I still need to run the spectrum analysis on the new system. I will post both spectrums after I run the tests. This afternoon I saw message rates up to 800 per second, and the plane numbers of 120/100. So far, only about 30 hours of operation. The overall range has not changed much with the additional 10 ft of antenna height. I believe the 3 pole filter is the difference. The filter has a 10 MHz bandwidth and reduces all other signals. I will post more as I get this working more.


#2

I have a couple of those 3 pole filters. I also special ordered some single pole 978Mhz UAT cavity filters.
They are great for a noisy location like NYC. I have 4 or 5 Mobile cells within a block or two.

Your stats look great. You will have the most A/C within a week.
This guy gets more position reports but could be in a better location
http://flightaware.com/adsb/stats/user/kq5m#stats-38787
You get 10 times as many reports at >200nm so I think you are doing pretty well.
Dave seems to get better reception to the East. Do you have something blocking that direction?

My suggestions, if any, would be

  1. optimise your gain settings
    Tweaks
  2. consider RF chokes on the USB pigtail(for the Prostickplus) if you use one and USB Power cable.
  3. put the RPI in a metal case to reduce noise getting into the dongle
  4. put the dongle in a metal case. I got some form https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ however, they no longer sell them.

I think your setup is pretty much the best value for money. My radarcape only gets about 2-5% more planes than the Fa Prositckplus.


#3

I do like how the filter is making a difference. With the higher message rate, I see the mlat message rates have suffered a bit. While I run the spectrum analysis options, I plan to copy the current microSD card over to a high speed Lexar 1800x microSD. I want to see if the current microSD card is a constraint on the system. All systems have constraints, the tough part is figuring out where they are and if they can be reduced. It may make no difference at all. I will report that back also.


#4

Quick update on changing my system to a high speed microSD card. Little improvement seen so far. The standard speed microSD cards should be just fine, no need for the expense of the higher speed cards. As always, your mileage may vary.

The most significant improvements are mounting the antenna higher with a clear view and using a better filter to remove the 900 MHz and lower frequency cell phone signals. Those two changes increased messages and flight counts by about 25% overall.