FlightAware Discussions

Trying to understand message rates

Depends what you want.
The signal level shows you that you are detecting some weaker messages than before.
Tone it down to -e 10 or -e 9, that will keep the message numbers basically the same and reduce CPU.
But besides maybe the pi using a bit more power, no drawback of using -e 11

I’ll ask again, you have the FA filter already?
Can you try it in front of the uputronics?

Thank you for the reply

Sorry I do not have a FA filter.
If I understand you well:

Antenna-> coax cable to FA filter->Uputronics->Airspy ->pi?
So this would mean two filters?

If so, I have to consult my Minister of finance :slightly_smiling_face:

Would like to get the “best” results possible in my situation.More planes doe not necessary mean more messages? At least that is what I see in the graphs.
It is still somewhat confusing, but making (baby) steps forwards in understanding

Not unlikely you have interference nearby that’s strong enough to partly mess even with the uputronics (already more resistent than the LNA in the FA pro+ stick).

But might not improve reception, kinda impossible to say.
Though i do agree that i’d expect a higher message rate in your area.

Well that is what I thought is so weird. Had a lot more messages just after plugged in the Aispy mini around June 21st.
Your explanation a few post back, made a lot od sense, even I could understand that. But I do not understand that the higher messages rate does not return.
Have been searching and looked around ven anything changed, but no extra GSM towers or something have been placed.

Will disconnect and connect tomorrow and see what might happen, if that would be an idea?
Will leave the settings as they are right now

But as always thank you very, very much for the assistance.

The green area (quartile) of his signal rate is pretty low and more narrow than mine. Can this impact his message rate?

Below is mine for the last 48 hours.
I am getting up to 1600 messages, but with a lower amount of ADS-B positioned airctaft:

And as a reference the ADS-B Maxima chart the last two weeks. One day is missing where the device was off for testing

here are mine:

But with these 48 hours it looks close to mine if you compare the ADS-B Position and Message rate.

No idea why you had higher rates before
On Saturday it’s expected that the approach direction for the different airports are changing. I can say that this impacts my graphs as well if it changes.

But maybe @wiedehopf has some further ideas

Well i’d expect him to have higher rates as he sees more planes than you and the planes he sees should be pretty active.
So the quartiles are in relation to the aircraft, he sees more of them further away … this will affect the distribution of the signal strength.

This is mine, i have the gain pretty low just because i like seeing the level change even when the aircraft get pretty close (don’t like aircraft at 0 :slight_smile: )
I might lose a bit of messages but i wouldn’t think it would be many.

But you have existing towers somewhat close by?
They could have been upgraded or something like that.

Does this impact also how wide the green spread is? His seem to be significant more narrow than yours and mine.
But honestly i have no idea what this all means

Looking on your message rate it’s pretty similar to mine (see previous post). is your aircraft count also similar?

Just trying to compare these numbers.

Few days ago i tried a one step lower gain, but without significant impact:

I haven’t notice maintenance work since my messages rates dropped, so that cannot be the reason

Tried to find something on the internet No clue what this means to our graphs. But perhaps you understand

Will start to disconnect and connect again today. Just as a desperate effort.

The signal level graph and what the green area means.
In the image you linked:

You sort the aircraft by signal level.
You divide the list into 4 parts.
The green includes the 2nd and 3rd part.
The 1st and 4th part are the white that remains above / below the green to the peak / weakest line.

The division between 2nd and 3rd part is the black line.

Same goes for range.

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Really, you can’t know that no changes happened.
There could be backup transceivers or whatever.
And again the usage could have changed for whatever reason.

Yes you are right, I was too fast with my conclusions. Sorry for that.
Guess I am hoping to find a reason and “solve”.
Till now it seems to be impossible :unamused:

Also thank you the explanation for the quartiles.

Well mobile interference is perfectly solvable by adding filtering.

Sometimes they change the coverage pattern for the transmitter/receiver (done remotely by software) and that may cause that you suddenly are subjected to more interference than before.

Thank you for the explanation as well.

If I understand well, I will have to invest in a FA filter and put it before the Uputronic. There us no way to change anything in the settings of the Uputronic?

It could help, yes. The Uputronic LNA is more sensitive to saturation than the tripple-filtered LNA from SDR-RTL. That said, it’s not super-sensitive, just not as robust as the tripple-filtered LNA.

The Uputronic LNA is hardware-only. No settings can be made, just different kind of filters that can be applied between the antenna and the LNA to filter out unwanted parts of the radio spectrum.
Different filters do that in different ways and can be quite cheap (filters from AliExpress etc can be good or total rubbish) or really expensive (cavity filters designed for 1090Mhz).

The FA filter is probably the most cost-effective filter you can buy for this application. It usually solves the problem with interference. It would be my first choice when cables, connectors etc has been ruled out as the source of problem.

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Thank you once again for your explanation.

@abcd567 posted a thread “Do I need a filter.” Will search as he posted a way to check the interference.
Perhaps this can give some more info. Thought I bought the right filter. And in the beginning it did. But as you guys (you, wiedehopf and fochunter) explained, there are other reasons my message rates dropped.

It’s speculation.
The only real way to determine if interference is the issue is adding a filter pretty much.
Doing a scan will certainly show interference but … GSM / LTE is always there and judging how strong from a spectrum scan is pretty hard.


Another scannig method, which covers interference in much wider band than covered by narrow band method described in "Do I Need A Filter? "

Spektrum - How-to Speedily Scan RF Noise in band 24MHz ~ 1800MHz

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