1.09 GHz filters
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1090 MHz informal filter tests

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

TA0970/TA1090EC-class
SAW from Golledge

 

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

Filter AS  Filter A1  Filter B

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

                 

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!

 

 
Copyright © David Taylor, Edinburgh   Last modified: 2013 Aug 16 at 07:52