FlightAware Discussions

Gain Adjustment


#221

For now I will let it run as is with gain lowered approx 14dB (from the Max Gain of approx 55dB).

BTW, how good is the preamp stage (transistor?) inside the FlightFeeder? Great one or just good enough?
As an experiment I might add a good preamp in front of the FF+1090 Filter and then lower even more the gain of FF (to match the introduced gain)… to the purpose of lowering the total noise factor. Of course, it is the risk that amplified signal might overload the input and make things worse.


#222

For a FF Orange, it’s the same as a prostick.


#223

Another option: Increasing attenuation
http://discussions.flightaware.com/post202030.html#p202030

.


#224

I think that the noise of the first stage will decrease more with decreasing amplification, so that’s usually a better option. Attenuation in front of it will mean that the gain/noise stays the same and this will decrease the signal/noise ratio.


#225

Hi,

Now I have my FA and mutability versions visually correct (range rings etc, thanks abcd!!) which of these script versions for testing gain, works with 3.5 mutability and fa ??

Jeff


#226

This whole gain thing is very interesting. I’m running the gain script over my two receivers now and have been for a few hours. Just watching the figures scrolling up the screen, it’s clear that the best gain at 07:00 in the morning isn’t necessarily the optimal gain at 13:00.

I wonder how practical (or desirable) it would be to run a script for a couple of days which returns the best gain for each one hour period and then once that’s been determined, to then change the gain automatically every hour by cron.

I’m sure that with far fewer aircraft in the sky in the late evenings and overnight, the gain can be set higher because there won’t be so many data collisions. Also with people going to bed at night and switching things off, there’s less QRM and therefore the natural noise floor should be lower.

Anyone feel up to the challenge of scripting this? It’s beyond me.

Or am I overthinking things?


#227

You have to compromise for the maximum daily yeld, depending on your location in respect to the normal busy lanes of airtraffic.
I can “see” two major lanes, one very close (from New England airports to Florida) and a further one, from same airports to Atlanta and such. For me a 42 dB gain is enough to minimize the clipped samples without loosing the far away planes.
But sometimes, because of weather, the traffic will move around, also at some weekends the traffic increase more in one direction than the rest of the week.


#228

Yeah, I probably am trying to overcomplicate things.

Anyway.

This has taken a little over nine hours to run today. The internal receiver took about ten minutes longer to complete the cycle which I suspect is simply down to it having a slower SD card.

I’ve set the two receivers at the highlighted gain settings above.

Interesting to see that there’s only 0.1% difference in the number of messages received between the two although the number of positions and aircraft seen externally is 2% and 5% higher respectively.


#229

Hi Keith
I will love to see how your J-Pole-on-mast compares with FA-aerial-on-mast.

Do you have any plans to move the JPole also to the mast?


#230

No, it’s not really practical to do that. The aerial is far from waterproof and I’m not really into the panel bashing side of things. The box at the top of the mast was built for me by a friend.


#231

Out of interest, when running the gain script, if the results are higher at different values for messages and positions, which figure would people choose? The one with more positions or the one with more messages?


#232

How to get script work with piaware 3.5.0 installed by APT method?


#233

None of the current gain optimization scripts suite following install:

(1) Write Raspbian Jessie image to microSD card
(2) Install Piaware data feeder (add-on package) by “sudo apt-get install piaware”
(3) Install dump1090-fa (add-on package) by “sudo apt-get install dump1090-fa”

Current scripts cover following installs:

(A) BratJr’s original script on Page 1: Raspbian Jessie + dump1090 MR / dump1090-mutability
(B) Lignumaqua’s enhanced script on Page 1: Raspbian Jessie + dump1090-mutability
© My enhancement on Page 3: Piaware SD Card image 3.0.1, but still valid for images 3.3 and 3.5.0

I will now work out modifications in the script for your case, i.e. "Jessie image + dump-fa & piaware install by apt-get"
It will then undergo trial run.
If all goes well, I will post the script.


#234

It seems like “piaware-config rtlsdr-gain X” is not working solution to adjust gain with jessie image + apt- method… Only way is modify gain value in /etc/default/dump1090-fa and then restart dump1090-fa


#235

It seems like “piaware-config rtlsdr-gain X” is not working solution to adjust gain with jessie image + apt- method…

Correct, this is a sdcard only option as documented at flightaware.com/adsb/piaware/ad … figuration


#236

I have modified and tested the script for “Jessie image + dump-fa & piaware install by apt-get”.
It works OK.
However when I tried to post the script, the forum says “Forbidden” :angry:

EDIT:
Due to recent restriction to post scripts in forum, I have now prepared Word files containing all different types of gain optimization scripts, and uploaded these word files to Dropbox.

I have provided the download links in the thread “TWEAKS”:TWEAK-3: Gain Optimization Scripts


#237

mod_security causing trouble…
If you have a github account then gist.github.com is not a bad choice for hosting something like that


#238

Thanks for the advice. Good idea.

Couple of months ago, I tried to open a github account with user name abcd567 and found someone has already taken it. :confused: :open_mouth: :frowning: :angry:

I have solved the problem by preparing Word files containing scripts, and uploading these Word files to Dropbox. Download links are avialable here: TWEAK-3: Gain Optimization Scripts


#239

[quote=“abcd567”]

Thank you!


#240

Link seems to be dead.