Here is my Saw filter
app never used it proper as i cannot get to lna amp connections
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I used to use a “nunu” filter:
It worked pretty well until one SMA connector broke off from the weight of the coax, which problem all bare PC board filters and LNAs will have. They really need to be in an enclosure with nuts holding the female SMA connectors snugly against the ends for support.
I’m currently using this:
which also works well though with 1.8-2dB of attenuation.
Just got an Airspy, so with the now spare orange flight aware dongle I decided to run some scans. Below are the results:
Just aerial into dongle:
Aerial into LNA then dongle:
Aerial into LNA then splitter then dongle:
Aerial into light blue FlightAware filter, the LNA then splitter then dongle:
Seems as though the LNA is dropping the GSM signal at 900 (but not much at 800), and making the 1090 more prominent. The splitter isn’t make much difference, but the Flight aware filter is eliminating to 800 and most of the 900. I did have the flight aware filter before the LNA, not sure if it would make any difference with signal etc if after (I have just moved it there, but can’t test of the moment as I am comparing the Airspy stats with the Prostick Plus for a day)…
To add to this, I now have the rtl-sdr LNA. So I ran the test again with that replacing the Uputronics one.
So: Aerial into RTL-SDR LNA then bais tee injector, then splitter then dongle:
As can be seen, the RTL-SDR LNA seems to filter out the 800 and 900 signals much better than the Uputronics.
Does anyone know what can possibly be running in the 1000MHz band? Seems like I have this interference near me on top of the cell phone bands. I know SAW filter made for 1090MHz will filter out the 850MHz ranges but will it also filter out the 1000MHz ranges? Thanks.
Hi! I use this LNA and posted my results before 
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Oops, I missed your earlier reply.
In my condition of total novice, I understand, or that the filter does not work properly, or that I have a very strong 900 signal nearby (I have a telephone antenna at 200m (600ft) in line of sight.
I’m waiting for an FA filter to see if I can eliminate that noise a bit on the 900.
Your scan shows that the Aliexpress Filter has done nothing to remove 900 MHz.
The FA Filter is really good, I am using FA Filters with 2 RPi’s, and got lot of improvement.
I use that LNA. I remove and short output capacitor for use with bias-t enabled RTL-SDR.com v3 dongle.
Getting the V3 Bias Tee to Activate on PiAware ADS-B Images
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I already have the FA filter. After trying it before and after the LNA, the best result is putting it after.
Ant-LNA-Stick
Ant-LNA-FA filter-Stick
Now I must test with different gain settings. The most observable thing at first glance is that at certain gain settings there are many more messages.
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I have feeders placed all over and they all use amplified and filtered USB sticks. My Pi’s have no problem seeing planes 250nm depending on the terrain they are in.
However, with the T620 that I set up I used NooElec Nano 3 SDRs. The reception is quite bit worse than the Pi’s. The SDRs are tuned so that one listens on 978 and the other on 1090.
I was thinking of getting a NooElec LNA and the FA 978/1090 combo filter.
The T620 is only getting planes out to about 50nm. Thoughts on if this would help the T620?
Thanks
T620 is quiet good, not inferiir to Pi. The worsening of reception is NOT due to T620. It is due to one or more of following reasons;
- Dongle
- Antenna type, location, height
- Type and length of Coax between Antenna and Dongle
- Gain setting of dongle.
If you want a realistic comparison, simply unplug dongle from Pi (with same antenna cable connected) and pug into T620, and set gain in T620 same as you have in Pi.