1090 MHz informal filter tests
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This page describes the results from informal tests of 1.09 GHz filters on reception of ADS-B signals. The results are from Plane Plotter, using its permanent trails feature with the heights coloured with conventional map height coding, so green trails are near the ground and brown/purple/pink trails up to 35,000+ feet in altitude. What I am looking for is the extreme range, to see whether the ~2.5 dB loss of the SAW filter is noticeable compared to the ~1 dB loss of the cavity and interdigital filters, and how much it affects maximum range. The data has been collected over a full weekday for each filter, to try and compare similar traffic patterns. Of course, the actual aircraft vary from day to day, and week to week, and summer-winter schedules, so the plots below can only be a general indication. Look for maximum range, not the density of the traffic. The receiver is a Mode-S Beast, and the antenna a Moonraker 6.5 dBd gain collinear. |
SAW filter - AS |
Multi-cavity filter A1 - re-tuned surplus filter Interdigital filter B - supplied by Bert
Modderman, PE1RKI |
Please note that due to gaps in the data collection some images are not present! Should you wish to use the same flight
levels and colours as I did, download this
text file, rename it to .REG (i.e. remove the .TXT extension), and run it
for your Plane Plotter by double-clicking. Save your own registry
settings for Plane Plotter first in case you wish to revert!
Saturday
Filter AS Filter A1 Filter B Filter C Hover your mouse over each of the links above to see the changes |
Sunday
Filter AS Filter A1 Filter B Filter C Hover your mouse over each of the links above to see the changes |
Monday
Filter AS Filter A1 Filter B Filter C Hover your mouse over each of the links above to see the changes |
Tuesday
Filter AS Filter A1 Filter B Filter C Hover your mouse over each of the links above to see the changes |
Wednesday
Filter AS Filter A1 Filter B Filter C Hover your mouse over each of the links above to see the changes |
Thursday
Filter AS Filter A1 Filter B Filter C Hover your mouse over each of the links above to see the changes |
Friday
Hover your mouse over each of the links above to see the changes |
Predicted Coverage
The plot below shows the predicted coverage from my location with aircraft heights of 2500 ft up to 40000 ft FL 400). The prediction program I'm using is Radio Mobile Deluxe, and it allow heights of up to 99999 m. It's difficult to compare the plot below with the permanent trail plots above - consider this just for fun. It's my first time of using that program, so I may easily have made mistakes! The key parameters I used were:
Network parameters: 1090 MHz, mode mobile, 50%
Base location, RX only, elevation 169.8 m (lower than the GPS here said...).
RX threshold -90 dBm, line loss 1 dB, antenna gain 6.5 dBd, height 6 m AGL.Aircraft, on the move, TX only, elevation 0m + variable.
TX power 100 W, line loss 1 dB, antenna gain 2.85 dBd,Network, membership, antenna heights: 762, 1524 3048, 4572, 6096, 7620, 9144, 10688 & 12192 m
and I would be delighted to accept advice if these are wrong.
Colour |
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Height |
2500 ft |
5000 ft |
FL 100 |
FL 150 |
FL 200 |
FL 250 |
FL 300 |
FL 350 |
FL 400 |
The measured filter responses
Filter A1 Filter AS Filter B Filter C Hover your mouse over each of the links above to see the filter responses |
Data measured with a DG8SAQ Vector Network Analyser - a very nice piece of kit!