Hi all, I’ve just installed a uputronics 1090 pre-amp to extend my range and messages. Unfortunately using a variety of gain settings it behaves worse than without the preamp.
System: Pi4, rtl-sdr dongle (official one), 1090 preamp (powered by usb-c), no filters, external antenna on a 5 metre cable run.
Location: Rural area in the countryside between Gatwick and Heathrow airports. Consistent daytime traffic for hundreds miles in all directions. No nearby mobile towers.
The graphs below start after I’ve installed the pre-amp. Red highlighted period is when the pre-amp was installed. I removed it at 13:10 on the graphs and range, aircraft and messages all went back to normal.
The numbers are the gain settings I tried while trying to ‘tune’ it.
I added a flightware filter to see if that would improve things but nada. (mentioned on graph)
The uputronics filter is suspectable to interference. I have one close to a TV and when it is on, the range goes down considerably. It would be great to see the graphs at night, when there may be less interference. The range drop in the evening is when the TV is on.
This is a mode S beast with a uputronics AMP and a cavity filter(Between ant and amp).
This is my bedroom setup(Close to the TV). It is only 15ft/4m Above ground and and about 40ft/10M AMSL. Some of the coax is quit thin.
This is an airspy with rtl-sdr 1090mhz amp in my attic. About 10 ft/3m directly above the bedroom setup.
The coax is much thicker on this setup.
Thanks ABCD, Jon and Dutchy for helping out with your questions/suggestions. To answer your questions:
Yes, the amp is powered using the usb-c charge point.
My antenna is a dedicated 60cm 1090Mhz antenna on 5m RG58 (RG213 on order). There a tree impacting east, but all other directions are clear and with plenty of traffic
No interference. Its extended above the roof of a shed at the back of the garden and is the only electrical device within 15 metres. No mobile towers in this small village either.
I receive out to the orange FL100 ring without the amp and much less with the amp
Whatever the setup I assumed the amp would help not hinder, after tuning the gain and trying with and without a 1090 filter. I’ve double checked the connections and pins. There must be something else I’ve missed but I cant see it in the graphs. Oh well.
Have you tried the FA filter in front of the LNA (i.e. between the antenna & LNA)? An easy thing to try and if things improve it would show there is some interference affecting the Uputronics.
Dutchyb had asked about the power. Do you see any difference when the power is removed? Does your unit have the LED that indicates power? That was something that was added in 2022.
Is your receiver connected to the port that is on the same end as the USB-C connector? My thinking there is could the case be on wrong?
I’d suggest putting any filter on the antenna side of the LNA. Then start with pass through (unpowered) to make sure you’re still getting what you’ve been getting. Then try very small gain on the Uptronics. Even 3 db is doubling the signal. If you see improvement you can notch it up a bit more until you either stop improving captured targets or begin to lose them. Then notch back to the best overall. It’s a “broadband” amp so it will amplify whatever is coming in. And if it’s set to too high a gain, you may be “amp’ing” disparate signals and noise which the RTL dongle can’t do anything with, but may get, electronically speaking, distracted by. I saw a comment from a EE on here somewhere, maybe he can validate my technician-level hypothesis.
Myself and a friend both use the Uputronics preamp and it works brilliantly compared to without. His is on the roof powered by bias tee. Mine is on a windowsill powered by USB. In both our cases it significantly increased messages, aircraft and range (full coverage in his case, covering all the UK south of Edinburgh, part of Ireland, northern France, Belgium, Netherlands and part of Germany).
They have been in various locations over the years and we’ve never seen the interference issues described from time to time. We’re using the Pro Stick Plus and LMR-400 coax and the FlightAware antenna. I was using CLF-200 coax until fairly recently.
In both our cases, without the preamp, the gain had to be set to the high-40s to maximise numbers and range. With the preamp the gain had to be reduced to the mid-20s to maximise numbers and range. We have adaptive gain and burst mode disabled.
We recently re-visited our numbers and tweaked them using the approach in this article, to maximise the spread of the RSSI figures, from around -1.5 for nearby aircraft to around -35 for very distant aircraft. In both cases the gain was moved by a single step and gave a slight improvement, so it was already about right.
What range of RSSI are you seeing when you enable that column and sort by it (click the column header to do so)?
If the preamp has no power then it does not pass through and nothing is received.
The preamp should go near to the antenna so that it is processing the signals as best as possible from the antenna, before they have been degraded from a run of coax. For a short run of decent coax and good connectors you can have the preamp next to the dongle instead. It’s less idea but saves having to remotely power the preamp with bias tee, or from having to put the whole lot outside and using power over ethernet.
Make sure your Pi’s power supply is good quality, ideally the official one, if you are powering the preamp from the Pi (eg using USB).
Thanks everyone for your replies and help. Its up and working now with much improved coverage.
I’ve implemented many of the suggestions. The biggest cause seems to have been an innocuous (or not so, as the case turned out) metal cabinet on which I placed the pi/uptronics. The pi always worked fine there but the uptronics didn’t like it. thanks again for the help
