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 Post subject: Why my reception quality was not significantly boost...
PostPosted: Thu May 18, 2017 11:59 am 
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jnrfalcon - FlightAware user avatar

Joined: Sat Dec 17, 2016 4:20 pm
Posts: 6
I have been feeding using the cheap TV stick with stock antenna for some time and just upgraded to Pro Plus + Nooelec 5dbi. The position of the antenna is roughly the same but indoor against outer wall on second floor.

This was just half day ago so I might be wrong. I see that the signal strength improved from around -20~-30 dbfs to around -5~-15 dbfs. But I'm still only mostly picking up planes within 75 nm. There are still a lot of dashes and dots. And I still have big trouble fully track planes taking off and landing just 10 mi from me...

Are all these because my bad positioning or there's something wrong with the settings... Or the Nooelec antenna is this bad...?


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 Post subject: Re: Why my reception quality was not significantly boost...
PostPosted: Thu May 18, 2017 12:25 pm 
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abcd567 - FlightAware user avatar

Joined: Sat Feb 15, 2014 3:08 am
Posts: 1980
Location: Toronto CYYZ
This may be due to either gain setting or RF Noise.
If it is due to high gain setting, lowering gain setting may improve range/plane count
If it is due to RF noise (strong Cell Phone signals), you will need to add a Filter

What is your gain setting?
If you are using Piaware image 3.5, by default it sets gain to -10 which is AGC (automatic gain control).
Reduce gain in steps of 5 dB to find at what point you get best reception/range


First check what is gain setting:
pi@piaware:~$ sudo systemctl status dump1090-fa

#If default gain settings are used, last line of output will show
piaware dump1090-fa[3585]: rtlsdr: enabling tuner AGC

#If you have adjusted gain to a value xx.x, last line of output will show
piaware dump1090-fa[506]: rtlsdr: tuner gain set to xx.x dB


How to reduce gain?
#Set gain to value yy
sudo piaware-config rtlsdr-gain yy

#Restart dump1090-fa for new gain value to take effect
sudo systemctl restart dump1090-fa

#Verify that new gain setting has taken effect
sudo systemctl status dump1090-fa

#Observe for some period the maximum range/ Plane count

Repeat above commands for several values of gain such as 50, 45, 40, 35, 30 ... etc.


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 Post subject: Re: Why my reception quality was not significantly boost...
PostPosted: Thu May 18, 2017 5:59 pm 
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jnrfalcon - FlightAware user avatar

Joined: Sat Dec 17, 2016 4:20 pm
Posts: 6
abcd567 wrote:
This may be due to either gain setting or RF Noise.
If it is due to high gain setting, lowering gain setting may improve range/plane count
If it is due to RF noise (strong Cell Phone signals), you will need to add a Filter

What is your gain setting?
If you are using Piaware image 3.5, by default it sets gain to -10 which is AGC (automatic gain control).
Reduce gain in steps of 5 dB to find at what point you get best reception/range


First check what is gain setting:
pi@piaware:~$ sudo systemctl status dump1090-fa

#If default gain settings are used, last line of output will show
piaware dump1090-fa[3585]: rtlsdr: enabling tuner AGC

#If you have adjusted gain to a value xx.x, last line of output will show
piaware dump1090-fa[506]: rtlsdr: tuner gain set to xx.x dB


How to reduce gain?
#Set gain to value yy
sudo piaware-config rtlsdr-gain yy

#Restart dump1090-fa for new gain value to take effect
sudo systemctl restart dump1090-fa

#Verify that new gain setting has taken effect
sudo systemctl status dump1090-fa

#Observe for some period the maximum range/ Plane count

Repeat above commands for several values of gain such as 50, 45, 40, 35, 30 ... etc.


I tried changing the setting and restart dump1090 but it still says enabling tuner AGC...


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 Post subject: Re: Why my reception quality was not significantly boost...
PostPosted: Thu May 18, 2017 6:09 pm 
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abcd567 - FlightAware user avatar

Joined: Sat Feb 15, 2014 3:08 am
Posts: 1980
Location: Toronto CYYZ
jnrfalcon wrote:
I tried changing the setting and restart dump1090 but it still says enabling tuner AGC...

What is your install? Have you written Piaware 3.5 image to microSD card, or have you written Raspbian Jessie image to microSD card, then installed Piaware 3.5 and dump1090-fa add-on packages? Or did you install dump1090-mutability? In each case, the method to set the gain is somewhat different. If you let me know what have you installed, I will tell you the method for that install.


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 Post subject: Re: Why my reception quality was not significantly boost...
PostPosted: Thu May 18, 2017 7:21 pm 
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jnrfalcon - FlightAware user avatar

Joined: Sat Dec 17, 2016 4:20 pm
Posts: 6
abcd567 wrote:
jnrfalcon wrote:
I tried changing the setting and restart dump1090 but it still says enabling tuner AGC...

What is your install? Have you written Piaware 3.5 image to microSD card, or have you written Raspbian Jessie image to microSD card, then installed Piaware 3.5 and dump1090-fa add-on packages? Or did you install dump1090-mutability? In each case, the method to set the gain is somewhat different. If you let me know what have you installed, I will tell you the method for that install.


Raspbian pixel and then installed piaware 3.5 and dump1090-fa. I'm developing it into a full system for other applications so I manually installed everything after clear system install.


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 Post subject: Re: Why my reception quality was not significantly boost...
PostPosted: Thu May 18, 2017 7:53 pm 
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abcd567 - FlightAware user avatar

Joined: Sat Feb 15, 2014 3:08 am
Posts: 1980
Location: Toronto CYYZ
jnrfalcon wrote:
Raspbian pixel and then installed piaware 3.5 and dump1090-fa. I'm developing it into a full system for other applications so I manually installed everything after clear system install.


In this case command "sudo piaware-config rtlsdr-gain yy" does not set the gain value. You have to edit the file /etc/default/dump1090-fa to change value of gain.

(1) Open file /etc/default/dump1090-fa in editor nano
sudo nano /etc/default/dump1090-fa

(2) Press Ctrl+w, then type word "gain" (without quotes), then press Enter key. The cursor will jump to the word gain.

(3) Right side of the word gain, you will see the value of gain. Since dump1090-fa is setting gain to AGC, this number is most likely -10.

(4) Change this number to the desired value of gain you want, for example 40.

(5) Save the file by pressing Ctrl+o.

(6) Close the file by pressing Ctrl+x

(7) Restart dump1090-fa
sudo systemctl restart dump1090-fa

(8) Check value of gain actually set by dump1090-fa
sudo systemctl status dump1090-fa


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 Post subject: Re: Why my reception quality was not significantly boost...
PostPosted: Thu May 18, 2017 8:42 pm 
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jnrfalcon - FlightAware user avatar

Joined: Sat Dec 17, 2016 4:20 pm
Posts: 6
abcd567 wrote:

In this case command "sudo piaware-config rtlsdr-gain yy" does not set the gain value. You have to edit the file /etc/default/dump1090-fa to change value of gain.

(1) Open file /etc/default/dump1090-fa in editor nano
sudo nano /etc/default/dump1090-fa

(2) Press Ctrl+w, then type word "gain" (without quotes), then press Enter key. The cursor will jump to the word gain.

(3) Right side of the word gain, you will see the value of gain. Since dump1090-fa is setting gain to AGC, this number is most likely -10.

(4) Change this number to the desired value of gain you want, for example 40.

(5) Save the file by pressing Ctrl+o.

(6) Close the file by pressing Ctrl+x

(7) Restart dump1090-fa
sudo systemctl restart dump1090-fa

(8) Check value of gain actually set by dump1090-fa
sudo systemctl status dump1090-fa


Thanks. Figured out by logging into root. What's the logic behind choosing a proper gain? I quickly tried several, mainly 50, none of them seems to have an immediate improvement yet... I wonder if there's a way that I can calculate what's best for me...


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 Post subject: Re: Why my reception quality was not significantly boost...
PostPosted: Thu May 18, 2017 8:56 pm 
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abcd567 - FlightAware user avatar

Joined: Sat Feb 15, 2014 3:08 am
Posts: 1980
Location: Toronto CYYZ
jnrfalcon wrote:
I wonder if there's a way that I can calculate what's best for me

Try this method:

http://discussions.flightaware.com/post199438.html#p199438


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 Post subject: Re: Why my reception quality was not significantly boost...
PostPosted: Fri May 19, 2017 11:13 am 
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jnrfalcon - FlightAware user avatar

Joined: Sat Dec 17, 2016 4:20 pm
Posts: 6
abcd567 wrote:


The performance is much better now. Not much better range but the signal consistency improved. Thank you so much :)


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 Post subject: Re: Why my reception quality was not significantly boost...
PostPosted: Fri May 19, 2017 1:55 pm 
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abcd567 - FlightAware user avatar

Joined: Sat Feb 15, 2014 3:08 am
Posts: 1980
Location: Toronto CYYZ
jnrfalcon wrote:
The performance is much better now. Not much better range but the signal consistency improved. Thank you so much :)

To know how much improvement is possible, you first need to know how much maximum range you can get from your location. Determine your physically possible Maximum Range using the method given in First Post of the following thread:

What is the Maximum Range I can Get?

Once you know what you can achieve, you can find methods to improve range. These include:

(1) Change antenna location and height so that it has an unobstructed view of horizon in most directions. If you cannot install antenna outdoors, try to locate it next to a large window or in attic.
(2) Use a better antenna
(3) Reduce cable attenuation by minimizing length of coax between antenna & DVB-T. The coax attenuation depends on type and length of coax. Up to about 10 meters of coax is ok when used with Pro Stick or Pro Stick Plus, as these have built-in amplifier, but even with these, reducing coax length improves max range / plane count.
(4) If RF noise is too strong, use Filter. The RF noise is caused by other strong communication signals such as Cell Phone signals.


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 Post subject: Re: Why my reception quality was not significantly boost...
PostPosted: Sat May 20, 2017 9:57 pm 
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jnrfalcon - FlightAware user avatar

Joined: Sat Dec 17, 2016 4:20 pm
Posts: 6
abcd567 wrote:
To know how much improvement is possible, you first need to know how much maximum range you can get from your location. Determine your physically possible Maximum Range using the method given in First Post of the following thread:

What is the Maximum Range I can Get?

Once you know what you can achieve, you can find methods to improve range. These include:

(1) Change antenna location and height so that it has an unobstructed view of horizon in most directions. If you cannot install antenna outdoors, try to locate it next to a large window or in attic.
(2) Use a better antenna
(3) Reduce cable attenuation by minimizing length of coax between antenna & DVB-T. The coax attenuation depends on type and length of coax. Up to about 10 meters of coax is ok when used with Pro Stick or Pro Stick Plus, as these have built-in amplifier, but even with these, reducing coax length improves max range / plane count.
(4) If RF noise is too strong, use Filter. The RF noise is caused by other strong communication signals such as Cell Phone signals.


More problems came = = So I was moving the dongle yesterday to find a better location. I stick the dongle on the way and use USB cord as extension rather than extending the antenna. So at one point when I was moving it, the tape was too streng and I broke the case of the dongle. I put it back no problem but the reception seems dropped hugely even we I moved it back to its original position (though the position of the Raspberry PI moved but I don't think that will affect anything right...?). You can find it here http://flightaware.com/adsb/stats/user/jnrfalcon

Did I broke something?


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