FlightAware Discussions

Decrease in range with Uputronics amp

Hi all,

A few hours ago I installed an Uputronics 1090mhz filtered preamp which arrived in the post today.

I installed it and played with gain, however the range has now decreased. I keep playing with gain but haven’t seen an increase in range.

When I remove the amp, it stays between 180-190nm.

Here’s my setup:

Without amp:
Pi 3B —> Pro stick Plus —> Dark Blue FA filter —> Antenna

With:
3B —> Pro Plus —> Uputronics preamp —> antenna

I have an outdoor antenna mounted on the roof. It’s quite a nice one from Piromoni. I’ll leave a link if you wish.

Any advice is greatly appreciated!

You’ll need to wind the gain back quite a lot, you could be getting swamped by close traffic and strong signals.

Also, the Uputronics amp is poor for nearby RF interference - Try putting the filter back in between it and the aerial and see if that helps.

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I had both setups. The dark blue filter is slightly decreasing the signal and a bit higher gain is required.
With the Uputronics you need to reduce gain significantly.
For me i needed to go down from 42.1 to 20.7. Otherwise the number of bad messages is way too high, the stick will not find the messages in that noisy stream.

For me the change to Uputronics slightly increased the range by 10-15 NM, but that is maybe also an impact by the better weather. At least it did not decrease

Put the Dark blue FA in front of the uputronics then and see if that improves the situation.
My guess is you have very strong interference.

You’ll also need to set the gain to probably 25 as you basically have 2 LNAs then.
If you want you can run this a bunch and let it correct the gain for you: Automatic gain optimization for readsb and dump1090 fa · wiedehopf/adsb-scripts Wiki · GitHub

You are remembering to feed power to the filter/amp, right? If not, it’s just a massive “resistor”.

@carstenks
You are faster in answering than I am. Wanted to suggets the same, as I did not power my Uputronics when I installed it the first time.

Thank you all for your replies!

I currently am powering the amp via a USB cable from the Pi.
Is this sufficient power, or does it need to be plugged into the mains with a brick?

I am also experimenting w/ and w/o the filter, and will run the gain optimization script and feed back to you.

Thanks a bunch!

I have currently a similar configuration
Raspberry 4B
Airspy Mini USB-Stick
Uputronics 1090 MHz LNA/Filter

The Airspy is connected on USB 3, the Uputronics is getting the power from one of the two USB 2 connectors of the Raspberry.

I tried it also with a simple Smartphone charger.
Both works for me without difference

Maybe not the most beautiful setup, but good for testing.
You need to make sure the Raspberry itself is powered sufficient.

There are rare cases where the Uputronics filter can get overloaded, but you probably would know if you have that kind of noise. So you will likely be better off not using three filters, or even two, e.g. Pro Plus stick (has a filter) → Uputronics LNA+Filter + Dark Blue FA filter. The FA add-on filter probably gives a couple db of insertion loss, so avoid it with the Uputronics if you can. Even then you still will have two filters when you might get the best performance with one! e.g. consider an orange FA Pro stick (no filter) + Uputronics.

For gain settings, the Uputronics adds about 13db of gain over USB and 4.5/5V bias tee from my experience. So as suggested earlier by someone, you need to decrease your gain. e.g. if gain in dump1090-fa was 48, you’d probably want to decrease it to around 33.8 once you add the Uputronics and test different gain settings from there. And many stations get even better performance by lowering gain another 5 to 10db from there.

Before i received my AirSpy, the Uputronics arrived. For two days i was using it in combination with the blue Flight Aware Pro Plus stick.

It’s a clear advantage using it, i was required to reduce gain from 42.1 down to 20.7, otherwise the messages > -3dBFS were way too high.

I have also the dark blue FA filter in one of my drawers. I got it some months ago and it was connected to the FA stick for a couple of weeks.
I needed to increase gain up to 44.5 due to the loss.

Beside that the FA filter did not give me any advantage, so i decided to remove it again. No idea where it would help, maybe in a noisy environment on the neighbor frequencies. For me it did nothing.

I also do not see the why having two filters in use , if both are covering the same frequency. Beside that the FA stick does have a filter for 1090 MHz as well. But i am not that technical expert to get this verified.

So it’s a clear yes for the Uputronics and a no for the dark blue FA filter.

No it’s not clear, you are generalizing which isn’t warranted.

We’re troubleshooting an issue here, for that using the dark blue FA in front of the uputronics makes a lot of sense as the uputronics LNA is set up much like the dark blue FA stick, so the filter is after the LNA which can overload.
The uputronics LNA doesn’t overload as easy as the blue prostick plus but it can.
Conversely the dark blue filter won’t reduce performance much at all, it’s 1.5 dB attenuation which isn’t very much.

The range reduction upon using a correctly powered uputronics 1090 LNA can’t have too many reasons, one of the plausible scenarios is strong interference.
And no not everyone knows there is a mobile phone tower somewhat nearby.

Something else to check: Any RP-SMA connectors on accident (missing center pin, otherwise looks like SMA).

One more thing you would have probably noticed, the uputronics LNA isn’t too tough and the SMA connectors can break off the board and become loose which obviously makes the signal much worse.

Have you tested adding the dark blue filter in front of the uputronics yet?

I currently do have the filter installed, and will change the gain every half hour or so as it is starting to get quite busy up in the sky where I am. I’ll repeat the same time tomorrow without filter, but it does seem to help a fair bit. I have a mobile tower one or two streets away, which was primarily why I purchased a filter a few months ago.

I will run a scan and create a heatmap of any interfering frequencies with and without the filter, which should help determine if it is necessary.
I will also take a close look at all connections, as I am going to be attaching and detaching the filter.

Thank you all for your help!!

According to the product page, it may have been fixed. But perhaps you refer to something else?

Since March 2020 we have fitted improved SMA female connectors for antenna input and radio output to address the issue of the SMA barrels coming away.”

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No i was not, seems to be fixed then.

Anyhow seems to be the mobile tower issue so my other guesses don’t apply.

So … i doubt it will get much better, you are likely terrain limited pretty much.
Check heywhatsthat: GitHub - wiedehopf/tar1090: Provides an improved webinterface for use with ADS-B decoders readsb / dump1090-fa
(the 2nd part needs tar1090)

I was not replying to the original question, but the statements directly above my posting
For sure it’s not generalizing, it is location and environment based as usual

According to heywhatsthat, may maximum range is about 260 nm. I have added the max. range ring to my map interface.

I live in a large residential area, but my aerial is mounted high up, so houses aren’t blocking the signals. There are a few tall trees here and there (and I mean very tall!). One of them is located in a vacant house, so probably not much I can do about that!

I have this aerial. In the future, I might look at purchasing the official FA one.

Anyway, going back to the Uputronics, I have run a scan without the FA filter and it shows a lot of interference, especially between 800-900mhz. So I will leave the filter installed, as another scan I run shows it is very effective at blocking these signals.

My range, with the Uputronics amp, has no longer decreased, but is staying roughly the same with the current config. (To clarify, that’s with the blue FA filter). I don’t think I will be able to extend my range much, but even if I can squeeze a tiny bit more, I will be satisfied. Otherwise, there would be no point in purchasing a £50 bit of kit!

Once again, thank you all!

Those 260 nmi are you sure they are correct? :slight_smile:
Also in all directions, or just one (where there might be no planes at high altitudes)?

Does your /tar1090/?pTracks look similar?

Could be your coax rather than the antenna but i don’t know if those antennas are good / consistent. High coax loss would preclude good reception.

I’ve had good luck with this antenna: COL1090/5-S
But the FA antenna is good as well, not sure how they would compare directly.