Is there a setting to Reduce Range?


#1

Is there a way to reduce the range of a receiver other than adjusting gain?

I have a two piaware receivers running (SD Card) 3.6.2 . One has a home made coco antenna that I use the get maximum range. The other I use with a stock whip antenna and I only want to show local traffic. The reason I do this is because I live in an area that is world heritage listed. I am under a flight path and there is a large group of people complaining about the number of planes flying overhead ( I love it ). A new International airport is being built nearby and residents are worried about the number of planes increasing. I like to keep a count as many seem to exaggerate the numbers.

So far I have experimented with antenna placement and adjusting gain. I have had good results but I find I have to keep tuning gain from time to time to only show traffic within 10 to 20km. I also end up counting some I dont want and missing some I do.

If I was able to filter out all traffic further than 20km from the receiver it would be perfect.

You can see the two receivers and range on my virtual radar here
http://fig.25u.com:8888/VirtualRadar

Long Range Stat Page
Short Range Stat Page


#2

Lowering the gain is the easiest way to do what you want. Keep the gain between 20 and 25. Other than the gain, an inefficient antenna is the other option.

By stock whip antenna, do you mean the little mag mount that came with the dongle for DTV reception? If so, do not trim it to the ADS-B frequency, and do not place it on top of a metal plane. That should be inefficient enough for your purposes.


#3

How are you counting aircraft? If you’re automating this, it seems fairly straightforward to exclude distant aircraft at that point.


#4

short range like you’ve tried not a problem by just reducing gain.
how would you avoid short range traffic while shooting for long range? I think inevitably you’ll get the short range traffic too.
maybe @obj has some idea how ‘to tell’ the software to reject traffic seen less than X distance.
my 2c.

evangel


#5

PIAWARE SD CARD IMAGE

(1) Before you start modifications given below, make a backup copy of file generate-receiver-config. This will enable you to revert in case something goes wrong during editing.

cd  /usr/lib/piaware-support/
sudo cp generate-receiver-config  generate-receiver-config.bak

#give command ls to check that backup copy is generated
ls

#above command will list files as follows:
fa_config_generator.tcl       piaware-console-status
generate-network-config       pkgIndex.tcl
generate-receiver-config      rpi-bootconfig
generate-receiver-config.bak  set-rfkill

.

(2) Open file generate-receiver-config for editing

sudo nano /usr/lib/piaware-support/generate-receiver-config

.
(3) Press Ctrl+w keys (search), and type max-range, then press Enter key.
The cursor will jump to the line containing --max-range 360. Please see below.
Change --max-range 360 to --max-range 20

proc generate_dump1090_config {config} {
        set dump1090config {
                {DECODER_OPTIONS="--max-range 360"}
                {NET_OPTIONS="--net --net-heartbeat 60 --net-ro-size 1000 --net-ro-interval 1 --net-http-port 0 --net-ri-port 0 --net-ro-port 30002 --net-sbs-port 30003 --net-bi-port 30004,30104"}
                {JSON_OPTIONS="--json-location-accuracy 2"}
        }

(4) Save (Ctrl+o) and Close (Ctrl+x) the file.

(5) Restart dump1090-fa

sudo systemctl restart dump1090-fa

(6) Check that max-range has changed to max-range 20

sudo systemctl status dump1090-fa -l

Following line in output of above command confirms max-range has been set to 20.
(scroll right to see it)

   CGroup: /system.slice/dump1090-fa.service
           └─1657 /usr/bin/dump1090-fa --net-bo-port 30005 --fix --device-index 0 --gain 45 --ppm 0 --max-range 20 --net --net-heartbe

.

max-range 360 (default)

.

max-range changed to 20


#6

hi @abcd567
any idea how can a particular range set can be selected ie only 150-250nm ?


#7

I thought this setting was for the map display only. So, if he feeds to FA, only the planes within the max-range 20 will be reported?

VRS has the same option, but again, I thought it was for map display purposes only. If not, VRS may be the best solution for the OP, as it’ll allow him to have reports.


#8

Sorry, I dont know how this can be done.

In SkyView there is a feature “Filter by Altitude”
Why not request a new feature “Filter by Range”

SkyView_filter-by-range


#9

I am not sure, but I think that for planes beyond max-range, dump1090-fa will pass data neither to map nor to output ports such as 30005 (from where Piaware gets its data to feed Flightaware).

This can be verified by running for one day with max range set to default 360, then change max-range to 20 and run for another day, then compare statistics of these two days on “My ADS-B” page.


#10

–max-range only affects position decoding (so: skyview and port 30003 output), not the raw messages (port 30005). piaware will continue to receive & decode all the raw messages regardless; it has its own internal setting for --max-range.


#11

@obj

Thanks Oliver for clarifying.


#12

Not necessarily, if the nearby signal is to strong it might overload the receiver and not be decoded at all.


#13

Thanks heaps for all the responses. It’s a shame that max-range doesnt effect the raw output on port 30005 as that would of been perfect to have the flightaware data recored the number of flights at close range.

I didn’t realize I could do reports with VRS so I suppose that setting max-range at 10nm and setting up the VRS database to collect the data I should be able to sort something out. As I feel the gain setting is working quite well for me at the moment. I do like how all the data is recorded and displayed at Flightaware, so I will get another raspberry pi set up and do some experiments on working with max-range and extracting data from VRS database and see what I can get working.

Thanks for all your input. You have all given me some great information that I can work with.