99% of the time the first stage of a modern LNA won’t be swamped by the antenna signal. 1% of cases are where the ADS-B antenna is mere meters away from an emitter one.
In those 99% of cases there is better utility to add that filter after the LNA, especially the LNA with SAW
filters.
PS: Contrary of what people think, GSM antennas are not emitting kW in strength, it would be useless to them to reach “far”, because they need to “hear” the cellphones return signal too. They are usually in the 10W range. Phones can do up to 2W and they have smaller antennas.
I pointed that up too a while back in this thread, that message rate needs to be correlated with the country the receiver is located in. And looking at the map you got, it seems that in France also depends of where exactly you are located, how far from major airports. CDG seems to be very interrogative, compared with the rest of France.
For example in US the numbers are about 1/2 of the ones in Germany.
Just had a case on another forum where the range was bad, filter was moved before the LNA and range improved significantly.
I consider it worth testing (at least if you already have the filter).
Quick Update from my still running tests, focussed on the far away aircraft to verify a range change.
The AirSquitter was mounted the last 24 hours on it’s original place.
It gave me today the first 14 hours (until 2pm) 19 aircraft in a range >320-400 km
At 14:00 i switched from the AirSquitter to my Raspberry with Airspy and Uputronics.
In the next three hours the number of aircraft > 320-400 km increased to 56
So i had 35 more in three hours only. This number i never achieved with the Airsquitter on a full day previously.
It also look like the Airspy can deliver a little more positions to FA, but that requires a real side by side monitoring for verification.
Still not representative, but a trend.
Testing in progress
The following shows a comparison of a RTL-SDR V3 + RTL Triple filtered LNA (red dots) with an Airspy Mini + Uputronics (Blue dots). I am running the Airspy Mini using a sample rate of 12, and a gain of 19. The same external antenna is used in both setups.
It should be noted that there has been a slight increase in traffic over the last 2-3 weeks + an increase in GA traffic on some days coinciding with a relaxation of some lockdown restrictions and better weather. However, I am pleased with the results and that I invested in an Airspy Mini and RPi 4, which was the start of this Forum theme.
Short update of my ongoing tests, of course not representative
Since yesterday i have the AirSquitter again on my main location with the Jetvision GPS antenna.
Seem to be that the slight increase of range was caused by weather or something, because the AirSquitter achieved now the same results as the Airspy from the range and messages
So i decided to test the Airspy/Uputronics combination on my second receiver in my home office indoor, replacing the FA stick.
The combination itself has a higher message rate (approx +20-30%) but not that much in the number of aircraft. The result is a higher message rate per aircraft.
The range went up by 20-30 NM for some individual aircraft, but it depends as usual from the traffic in general. Especially in the afternoon it went down, so a comparision doesn’t make much sense.
Interestingly the blue FA stick combined with the Uputronics also deliver a very good performance compared to the FA stick only, but the Airspy still goes a little higher.
So if someone does not want to pay that extra 120 Euro for the Airspy, i think it’s a good combination.
My personal resumee for this day (without claiming completeness or accuracy)
The Airspy/LNA combination has advantages in rough environments where the signals are not that good.
So i will maybe keep this for my indoor receiver and move the blue FA stick to the new side.
Is the first graph your FA stick?
With a max message rate of 1855 i doubt that. The FA stick is not known for such a high message rate.
What was the number of aircraft displayed?
Yes, this was also part of the discussion some months ago that the RTL-SDR can outperform the FA stick. I am still struglling with the search engine here.