Local Municipal Airport


#1

Folks,

Reading up on the forum I see one poster, who is very close to an airport, says he loses signal when aircraft are very close on landing or take off.

I live within 3.5 miles of a local airport, just light aircraft traffic.

I am intending trying a portable project with my PiAware but this will put me close to the aircraft; now I am assuming the light aircraft don’t have the powerful transponders of commercial aircraft so will this close proximity affect my receiver?

I only use a basic USB dongle and supplied aerial on a tin can.

Geffers


#2

@send2gl:

Seven Months ago, very close to Toronto Pearson Airport CYYZ…

With my Android Phone + OTG cable + DVB-T Dongle (generic) + dongle’s whip antenna on a tin can + Flightaware’s “Flaght Scanner” App on my Android Phone.

An this is what I got:
Screenshot_2017-05-18-18-06-55


#3

If you’re using an SDR dongle then you may need to decrease the gain significantly to improve reception of very close (higher power) signals. This is common. It’s also a trade-off as you may lose some reception of distant signals. You will want to experiment with gain settings to find a satisfactory compromise. There are other threads in the forum which discuss gain adjustments.


#4

All transponders have to meet the same specs. Be it a light sport aircraft or a 747.


#5

All transponders have to meet the same specs. Be it a light sport aircraft or a 747

That’s not true in several ways: frequency used, antenna diversity, transmit power, etc.


#6

The receiver reports the signal strength on the RSSI (relative signal strength indicator). Usually RSSI values close to 0dB to -2dB are too powerful. If you want to see nearby planes you should lower the gain until the strongest signal is around -3dB.

Plane transponders output around 30W to 500W+. This is why a far away plane can have a RSSI of around -20dB and a close plane will have a -20dB signal. The far away high power transponder will have the same signal strength as the close by lower power transponder once it reaches the receiver.

Setting the PiAware gain from 16 to 24 is good when close to an airport. Default piaware gain is -10 (full gain with AGC on). Gain setting can be set from 0 to 50.


#7

A British Airways 777 at 8000 feet almost directly above is showing between -3.3 and -5 dBFS so am guessing setting is fine for my location.

Does it need a reboot to change gain settings?

Geffers


#8

.

After changing gain setting, reboot for implementing the new gain value.
This is applicable for both Piaware SD Card image and Piaware Add-on package install.


#9

The easy way is to reboot the device for the new gain setting to take effect.

A faster way when able to ssh into the device you can run the commands

set the gain to 30

piaware-config rtlsdr-gain 30

restart the decoder with the new gain setting

sudo systemctl restart dump1090-fa


#10

They ALL have to meet the same spec. Yes, 978 has a lower power output, however, this is in the context of 1090. Clearly, this person isn’t listening to 978. We all transmit on 1090mhz with the same minimum specs. Come’on, you really want to fight this? It’s in the TSO docs and specs for ADS-B compliance.


#11

Thanks David. The method you described applies to Piaware SD card image, but @send2gl has Piaware Add-on package, and in case of Add-on package, the command
piaware-config rtlsdr-gain 30
will change setting only in piaware config file, but NOT in dump1090-fa

Please see this new thread I have created few minutes ago which covers both types of installs (i.e. Piaware SD Card and Piaware Add-on)

For Beginners - How to Set / Change Gain


#12

Nice catch abcd567. The commands I posted only work for the PiAware SD card image.

A British Airways 777 at 8000 feet almost directly above is showing between -3.3 and -5 dBFS so am guessing setting is fine for my location.

The PiAware system will not report anything lower than around -2dB RSSI. These really strong messages will not show up at all and you will not know if you are missing messages until you lower the gain to check for them. If nothing is found you can raise the gain back up.

That being said, if the RSSI is showing -3.3dB for the closest plane you have your gain optimally setup for close by planes.


#13

What transponder specification, specifically, are you referring to that both a light sport and 747 have to meet?


#14

The Transponder power output can vary.
I think the helos I fly pump out about 200W but the 747s/A380 are closer to 500W.

Here is one typically used in GA aircraft.


It puts out 250W.

This one is only 200W