FlightAware Discussions

Uputronics Preamp + FA ProStick Plus

Since my last thread, my setup received some much needed upgrades.

It is now as follows:

RPi 3B+ —> FA ProStick Plus —> FA ADS-B 1090MHz Filter —> LM400 Coax —> FA 26" ADS-B antenna

The cable connecting the antenna to the rest of the equipment is 50 ft long and I feel like that is restricting its abilities. I ordered an Uputronics ADS-B Filtered preamp and had a few questions about installing it:

It’s powered either by bias-tee or the mini-USB port on the side.

Does the FA ProStick+ dongle supply bias-tee power or will I have to power the preamp externally?

My Raspberry Pi and my wireless access point are inside the house, protected by a small UPS in case of a power outage.

The antenna is on the roof, far away from the RPi. There is power on the roof, but there is no UPS, so if the preamp was powered through it’s mini-USB port from the roof power, and there was a power outage, would my RPi continue to receive data with reduced performance or would it not receive any data at all due to the preamp not running from lack of power?

The Uputronics preamp has SMA on both ends. My coax cable has SMA on one end (the side that currently plugs into the FA filter), and N-type on the other one, which is what plugs directly into the FA 26" antenna.

Since I plan to install the preamp right behind the antenna, I would need an N-Type to SMA adapter or cable, and then another SMA to N-Type cable to connect the other end of the preamp to the antenna.

How much would adapters/cables affect the performance of the preamp in this situation?

How much of a performance gain would I be looking at if I just installed the preamp inside the house? If I were to do this, would the preamp be installed after the FA filter, as shown below:

RPi 3B+ —> FA ProStick+ —> FA ADS-B 1090MHz Filter —> Uputronics preamp —> LMR400 Coax —> FA 26" ADS-B antenna

Or before the filter?

RPi 3B+ —> FA ProStick+ —> Uputronics preamp —> FA ADS-B 1090MHz Filter —> LMR400 Coax —> FA 26" ADS-B antenna

Would really appreciate your help.

Your signal is going in the wrong direction :slight_smile:

It does not have a built-in biastee. You can buy a bias-tee though and connect it near the pi.
An unpowered LNA generally blocks most of the signal, reception would be terrible.

Before answering your other questions… 50 ft of LMA400 isn’t bad at all i wouldn’t expect any significant difference.
I’d first try installing the LNA where the coax meets your receiver.
Leave the filter in … it doesn’t hurt and can help.
If you assemble it rigidly be sure to unplug the SDR from the USB to avoid bending moments on it. After connecting everything be sure the assembly is kept in place in a way that doesn’t bend the SDR and USB socket.
In case that doesn’t yield good results one can try the filter before the uputronics.
Mind you i’m talking about the signal path, the signal comes from the antenna and travels to the SDR.

Overall i think you’re just terrain limited … to determine that i’d use tar1090 as follows:

/tar1090/?pTracks combined with a terrain outline will give you a good sense of how much range you can get versus what you’re actually getting:
https://github.com/wiedehopf/tar1090#tar1090
https://github.com/wiedehopf/tar1090#heywhatsthatcom-range-outline

Graphs will give you a good comparison between days i’d install it as it often gives good clues about changes in the reception:
https://github.com/wiedehopf/graphs1090#graphs1090

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For what it’s worth, because the Uputronics and Pro Stick Plus have their own filter, I see better performance after removing the inline 1090 filter. :man_shrugging:t2:

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In which position?
Also how do you judge better performance, that can be really difficult.
Anyhow … with RF stuff … whatever works :slight_smile:

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Overall i think you’re just terrain limited

I definitely am. The area I live in is not flat, my street sort of inclines upwards and my house is on the lowest part, add that to the fact that the airport nearest to me has stopped commercial operations and all commercial flights moved to a new airport 40 km away.

I thought being limited by my surroundings AND having my antenna fed by a very long coax run (compared to most on this forum) would hurt my results and after reading multiple posts on different forums recommending LNAs for people in situations like mine, I thought buying one would improve my results since they seem to do so for everyone else.

Well make the panorama, stick it on the pi via the commands in the link and check your actual coverage vs theoretical coverage.
That will give you actual data.

Were those posts commenting on LMR400? That’s 4.4 dB loss per 100 ft so around 2.2 dB loss for 50 ft.
That loss is usually not critical when talking ADS-B.
So i’m suggesting the posts you’re referencing aren’t necessarily the same situation.

If you’re keen to place the LNA in a weather proof enclosure and fiddle with the adapters mentioned go ahead but i don’t think it’s worth the trouble.
Using the LNA in general near the receiver is worth the experiment, you’d expect a mild improvement as the uputronics is a good quality LNA filter combination.

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I have a similar setup, but I used cheap RG6 coaxial cable, pre-terminated with weather-proof F connectors.
I used the FA antenna cable (3-5 meters) to plug into my LNA/Filter SMA connector, then I used an SMA-F adapter to plug in my 50 meter RG6 cable.
In the house I have added a gas surge protector, the power T injector, and final F-to-SMA adapter to connect to the receiver. I have also used a short SMA-SMA extension, to be more flexible at the Pi end (the RG6 cable is very rigid).

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