I am trying to tidy this up a bit by posting the testing results here in PDF form instead of stringing them throughout the thread.
Revised 978 MHz UAT Antenna Analysis: (Posted 24-Aug-2016):
Revised document to correct Plot labels. Combined the split charts into one chart based on GPS time stamp (i.e Plot 2a and 2b combined into a single plot 2). Added a histogram summary chart for all antennas that were mounted over a ground plane.
978 MHz Antenna Analysis V3a.pdf
978 MHz UAT Antenna Analysis: (Posted 24-Aug-2016):
Added the Digikey (Linx) ANT-916-CW-HWR-SMA-ND antenna to the 978 MHz Antenna Analysis document.
978 MHz Antenna Analysis V3.pdf
978 UAT Antenna Analysis: (Posted 23-Mar-2016):
This is an analysis of various 978 MHz UAT antennas. Version 2 added "no ground" data for the remaining antennas.
978 MHz Antenna Analysis V2.pdf
Impedance Analysis (Dongle, Splitter, and Antenna): (Posted 05-Feb-2016):
Impedance Analysis.pdf
Correction: the document states a "2V USB Wall Wart Power Supply." This should be a "2A USB Wall Wart Power Supply."
Chris, if you don't feel this belongs here you may take it down.
I, like many have been curious about the performance of my Stratux unit and as such I wanted to quantify its performance.
My Stratux comprises of the R-Pi 2 B, a RY835 GPS / AHRS, 2 of the original T2 RTL-SDR dongles and various antenna configurations used during testing and version 0.5r5. The pictures of my Statux build are available here: http://imgur.com/a/G085R
The antenna configurations will be discussed later. The test method was to select an antenna configuration, capture the Stratux logs and post process and analyze the data.
Test Configuration Number 1:
The first test configuration consisted of a tuned Diopole Vertical antenna (one at 1090 MHz and one at 978 MHz) connected directly to the SMA connectors on the Startux unit. Stratux was place on the dash board of my truck and was parked in a field behind the hose with a clear view to the sky to the north. The cab and body of the truck shielded the Stratux reception to the south. A 15 minute recording was taken and 1090ES data was post processed. The data consisted of anywhere from 1,500 to over 5000 1090ES hits. The range to the detected traffic was calculated using the Haversine Formula with my truck location at the center. A Track Plot was created to visualize the range and bearing of the traffic. These track plots utilize the same methods to analyze TCAS performance data. This is a Track plot of the first configuration.
As can been seen in this plot, the range approaches 170 nm. This is not bad for an off the shelf RF dongle. Now I had a baseline to use for the rest of the testing. (It appears the range is limited due to the view angle of the traffic from my location. I'll add more about the view angle at a future date.)
Test Configuration Number 2:
This configuration removed both tuned antennas and feed both dongle via the tuned 1090 MHz antenna and an SMA "T". Conventional wisdom would say that there would be a 3 dB reduction on power to each dongle and thus a reduction in range by at least one eighth. This is otherwise know as the invers square law: Where if you double the distance, the power at the receiving antenna is one forth the previous power lever. Let's see how the looks in practice.
The above plot still shows a range out to 170 nm. Based on this data, we still haven't lost reception of the traffic before is moves out of our view.
Test Configuration Number 3:
Test configuration was like Configuration 2 except the 1090 MHz antenna was replaced with the tuned 978 MHz antenna.
Notice the range and number of targets are reduced. The range decreased 26% from 170 nm to 126 nm. What suggests is the tuning of the antenna to the frequency of interest is of more importance than whether it is feeding to the SDR directly or through a "T".
That's it for this installment. Next up is an in-flight performance analysis and an analysis of the view angle.
cyoung
commented
6 years ago
I am trying to tidy this up a bit by posting the testing results here in PDF form instead of stringing them throughout the thread. Revised 978 MHz UAT Antenna Analysis: (Posted 24-Aug-2016):
Revised document to correct Plot labels. Combined the split charts into one chart based on GPS time stamp (i.e Plot 2a and 2b combined into a single plot 2). Added a histogram summary chart for all antennas that were mounted over a ground plane. 978 MHz Antenna Analysis V3a.pdf
978 MHz UAT Antenna Analysis: (Posted 24-Aug-2016): Added the Digikey (Linx) ANT-916-CW-HWR-SMA-ND antenna to the 978 MHz Antenna Analysis document. 978 MHz Antenna Analysis V3.pdf
978 UAT Antenna Analysis: (Posted 23-Mar-2016): This is an analysis of various 978 MHz UAT antennas. Version 2 added "no ground" data for the remaining antennas. 978 MHz Antenna Analysis V2.pdf
Impedance Analysis (Dongle, Splitter, and Antenna): (Posted 05-Feb-2016): Impedance Analysis.pdf Correction: the document states a "2V USB Wall Wart Power Supply." This should be a "2A USB Wall Wart Power Supply."
1090ES Traffic Analysis (Posted 28-Jan-2016): 1090ES Traffic Analysis.pdf
Emissions Testing (Originally Posted 25-Jan-2016): Stratux Emission Testing.pdf
In Flight Data (Originally Posted 13-Jan-2016): In Flight Data.pdf
Performance Analysis (Originally posted 12-Jan-2016): Performance Analysis.pdf
Chris, if you don't feel this belongs here you may take it down.
I, like many have been curious about the performance of my Stratux unit and as such I wanted to quantify its performance.
My Stratux comprises of the R-Pi 2 B, a RY835 GPS / AHRS, 2 of the original T2 RTL-SDR dongles and various antenna configurations used during testing and version 0.5r5. The pictures of my Statux build are available here: http://imgur.com/a/G085R
The antenna configurations will be discussed later. The test method was to select an antenna configuration, capture the Stratux logs and post process and analyze the data.
Test Configuration Number 1: The first test configuration consisted of a tuned Diopole Vertical antenna (one at 1090 MHz and one at 978 MHz) connected directly to the SMA connectors on the Startux unit. Stratux was place on the dash board of my truck and was parked in a field behind the hose with a clear view to the sky to the north. The cab and body of the truck shielded the Stratux reception to the south. A 15 minute recording was taken and 1090ES data was post processed. The data consisted of anywhere from 1,500 to over 5000 1090ES hits. The range to the detected traffic was calculated using the Haversine Formula with my truck location at the center. A Track Plot was created to visualize the range and bearing of the traffic. These track plots utilize the same methods to analyze TCAS performance data. This is a Track plot of the first configuration.
As can been seen in this plot, the range approaches 170 nm. This is not bad for an off the shelf RF dongle. Now I had a baseline to use for the rest of the testing. (It appears the range is limited due to the view angle of the traffic from my location. I'll add more about the view angle at a future date.)
Test Configuration Number 2: This configuration removed both tuned antennas and feed both dongle via the tuned 1090 MHz antenna and an SMA "T". Conventional wisdom would say that there would be a 3 dB reduction on power to each dongle and thus a reduction in range by at least one eighth. This is otherwise know as the invers square law: Where if you double the distance, the power at the receiving antenna is one forth the previous power lever. Let's see how the looks in practice.
The above plot still shows a range out to 170 nm. Based on this data, we still haven't lost reception of the traffic before is moves out of our view.
Test Configuration Number 3: Test configuration was like Configuration 2 except the 1090 MHz antenna was replaced with the tuned 978 MHz antenna.
Notice the range and number of targets are reduced. The range decreased 26% from 170 nm to 126 nm. What suggests is the tuning of the antenna to the frequency of interest is of more importance than whether it is feeding to the SDR directly or through a "T".
That's it for this installment. Next up is an in-flight performance analysis and an analysis of the view angle.