20/sec is very low - right now (late evening, terribly placed antenna) I see 150/sec here.
My antenna is in the window, “looking” straight at the planes, no building around. Can it be the gain that has a wrong setting? Right now it is set at -10 (AGC).
nope - this is in most cases the best (because highest) gain and even higher than max. but simply try the lower settings like 50, 40, 30. maybe high power mobilephone stations are near - then a filter could help. best is cavity-filter, second best uputronics filter/amp. if there is lot of noise on 960 mhz then the external fa-filter is the wrong choice. if possible try to open the window and see if then reception is better - some types of windows have metallic foils. test your antenna connection cables and plugs often there is a problem - must always be male to female - always a pin that sticks in a hole …
I ordered a new antenna and filter. I’ll keep you posted with the results. BTW I tried opening the window – no change.
As promised here’s the follow-up : New antenna + filter = 300% more planes and the messages/sec went up from 25 to a hundred. Thanks to you all once again!
very cool that in the end anything is fine
Hi Yvesbloche ! Can you tell me what antenna and what filter did you get? It seems I have the same problem than you and I would like to fix it… thanks !
Antenna (1090MHz ADS-B Antenna - 66cm / 26in) and filter both by Flightaware available on Amazon.
thanks ! Just got it ! I will let you know if it works better on mine
ACG (Gain -10) is totally un-adequate for this kind of signals. It is meant for just ONE signal, stationary, with the amplitude integrated in time.
Our planes are many signals, with diverse levels, arriving at close-apart times, from moving targets (variable level).
Just set the gain at different levels and watch that number for a few seconds, than change it again.
Also, on the web page map, if you see lots of planes, like 20 miles out, with levels like -1.5…-2 dB, than the gain it is certainly too high and lots of signals from close-up planes are getting clipped.
I agree! I’ll go as far as to say that the -10 option should be removed altogether.
My receivers are indoors, and still go deaf when -10 is used. I changed the one without a preamp to 49.6, and the results are excellent.
The receiver with a preamp, and filter, works best at 20.7.
The AGC setting (-10 gain) actually increases the gain by about 3dB so the theoretical max gain is around 53dB. This is the best way for someone to see an actual plane during initial setup. In our test we also know people are not using amplifier or higher gain antennas and these setups need all the gain they can get.
The external and internal amplifiers on the market increase the front end gain from around 13dB to 25dB (depending on the brand). And the high gain antennas are in the 6dBi to 8dBi range. This will usually overload the receivers if the gain isn’t reduced.
Here are some details that are missing:
- The RTL dongles are fairly noisy internally. They have a noise figure of 3dB to 7dB. The vast majority of RTL dongles are in the 3-4dB range.
- The less internal receiver gain used the lower the internal noise. Using external amplifiers increase the gain while also decreasing the internal receiver noise. This is the main reason why a dongle set at 50dB see less planes than an external amplifier (20dB) and a receiver set at (30dB). The external amps are much lower internal noise.
- The RTL dongles have gain is from 0 to 50dB with a ~3dB gain extra on the AGC circuit. The AGC is much noiser but the 3dB gain usually offset the problem.
- The RTL dongles front end is “wide open”. This means that the internal filtering stage is after the gain stage. If you use an external filter you aren’t amplifying noise in the internal amp.
- The RTL can get hot. Cooling the RTL dongle a bit doesn’t lower the noise. Active cooling system (refrigeration or putting in a sub zero environment to lower temperature close to freezing) can gain 1-2dB.
There isn’t much to gain from cooling.
- Gain settings are very location dependent. One gain setting will not always work when moved to another site.
- ***The main place to gain range is to get better amplifier and filters. ***
- ***The second place to gain range is in the antenna. ***
I agree with all you said, but the -10 setting creates an interesting situation. Using 49.6 db, my noise level is -30 dbfs, the average signal is around -10 dbfs, peaks are around -1.5 dbfs.
The extra 3 db added by the -10 setting, brings the noise level to -3 dbfs, and the signal to -2 dbfs.
In addition to that, -10 confuses new feeders. How many times people assumed they could try different settings in the negative domain? If 53 is not available as a level in its own right, consider making 49.6 the default to simplify things.