Trying to understand message rates

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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Thank you, I am using a mac and read the thread. Guess will have to wait some time :slightly_smiling_face:


Jan 7

It’s been my plan all along to append to your great guide. It will just take some time. (This update took me 3 days to write :sweat_smile: )

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

The results of scans are below:

The scan 1 shows RF noise picked by antenna and processed without any filter , The scans 2 & 3 were done with filters, and show how filters remove this noise.

Scan 1 of 3 - FA Antenna + Generic DVB-T (no internal or external filter)

Thumb-Generic DVB-T


Scan 2 of 3 - FA Antenna + ProStick Plus (Only Internal filter of ProStick Plus. No External filter)


Scan 3 of 3 - FA Antenna + ProStick Plus (with internal filter) + External Filter (FA Light Blue)



Hello All,

I am still struggling and getting more and more frustrated. Still reading as much as possible and taking in all the comments in this thread.
I am still not having the FA filter and have not been able to check what @abcd567 suggested.
Even my Aircraft seen is dopping. But noticed this:
Schermafbeelding 2021-07-26 om 20.16.04

Schermafbeelding 2021-07-29 om 19.01.51

Fewer planes and still more or less the same message rate.

Undoubtedly there will be an explanation, but I can find it or think of it.

Perhaps I am asking too much or you guys are getting annoyed, so please forgive my asking.
My settings
Airspy mini
Jetvision A3 Antenna
Gain 18
OPTIONS= -v -f 1 -e 11
Uputronics powered by Mini USB to my Pi4

Please forgive my rambling :cold_sweat:

PoP your graphs1090  up  it will explain a little more 

sorry forgot to do that.

Also as @wiedehopf suggested. My CPU is 80% after using the -e 11 option.

If it helps, these are mine with similar number of aircraft. The only difference is the Vinnant antenna, but i get the same results with the A3.

You should not look on the total number, but filter on ADS-B. This is the dark blue line in the Aircraft charts



I have filtered on ADS_B only, while making the screenshots of the messages rate.

Anything is depending on the number of aircraft in the sky. I have falling numbers as well, there have been some pretty bad days for GA aviation in NL. First thunderstorms, yesterday and today high winds. A lot of aircraft you pick up is related to GA, on average I have 1500 adsb aircraft on a day. In comparison, last week I had 2000. GA is on average 25-35 % of all air traffic in NL. If I look at hits, I sometimes have a drop of 40-50 % if there is little GA activity. So ride it out, there isn’t much you can do other then making sure everything is connected well and that you are recieving. I’m sure sunny days will come and then you will see a rise in aircraft numbers and hits again. It is still a hobby, don’t let it frustrate you :wink::innocent:

I think his question is more related why the message rate dropped while the amount of aircraft did not change.

In my region Tuesday is the lowest traffic day and then continously increasing to the weekend.
If you follow the thread, he had a significant drop in message rate without explanation.

Looking on your FA stats you have a drop some days ago. I stated already it could be a weather change. As you’re close to AMS, maybe you’re impacted by the approach direction as i am in FRA.

I would wait until the weather condition changes again.
For FRA there is a “Betriebsrichtungprognose” available which gives you a forecast from which direction the aircraft are coming in the next days
Not sure if something is available for AMS as well and how much impact they have based on weather


Ok will try to be patient and wait. And of course will check out the link you provided

If you look at my stats, then you can see similar drops that are actually related to the weather :wink:
I have 4 separate feeders, and all show the same behaviour. The number of hits is variable, the aircraft count is on average the same :wink:

Have you already used for checking the distance from your antenna to the nearest cell phone towers using the 950MHz band?
I have one at less than 200m and when I added a 1090MHz cavity filter between my antenna and the LNA the message rate and number of flights increased by 30%!


Thank you for the link. Did not know it I could check it myself. Pff, knew there were “some” in my neighbourhood, but that many. Name it, and it is there.
Schermafbeelding 2021-07-30 om 16.10.59

Guess will have to look for an extra cavity filter.

Saw one in the Jetvision shop for Euro 196!!!

If you buy the flightaware filter it will be 30 euro’s :wink: