BiasT recommendation

Hello, looking for BiasT recommendations as I want to install the uputronics LNA on a 15cm patch lead from my antenna but the RTL-SDR only outputs 4.5v and the LNA spec is 5-26v

you could power it from a USB port ( if you are using a Raspberry Pi offcourse). Standard voltage for a USB port is 5 volts.

It’s currently powered from a USB on my PI, but I want to install it as close to the antenna as I can but need a BiasT after dongle though.

Ah my mistake, I thought you had only 15 cm between the Pi and the antenna but that’s the dongle and the antenna.

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I use one very similar to this: Bias Tee 10MHz-6GHz Broadband Radio Frequency Microwave Coaxial Bias SoftwaBias 4894909151576 | eBay

It’s a bit more expensive than when I bought it, but that seems par for the course these days. It works fine. You could also try the amp on the built in dongle bias-t. You might find the 0.5v difference isn’t significant enough to make a lot of difference.

The standard board doesn’t have the VReg for such a wide input. You need to add it yourself if you need it.

I’m just going off what it says on the uputronics website and on the case itself, so I have to open it up and add something if I want to use bias T on it?

„ 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. Also the Bias Tee regulator kit is now fitted as standard. At this time a ceramic filtered version of this unit is no longer available.“

From uputronics website, maybe that allows you to run the bias t voltages mentioned?

Good start.
Easier to just check the specification of the LNA:
1090MHz ADS-B Filtered Preamp

A regulator is fitted as standard which means the bias-tee voltage input range is 5V to 26V. USB input is 5V.

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Have you tried?
Pretty sure it’ll just work.

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Well spotted. I went to the data sheet and it still shows the PCB without the reg.

From the pic I’ve found, I can’t ID the amp chip, but it’s a fair assumption it’s not higher than 3.3V.
That allows 1.2V drop across the reg for a 4.5V input.
There is a very high probability that’ll work fine.

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The chip is a MiniCircuits PSA4-5043+

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Excellent - thanks.
The PSA4-5043+ only wants 3V, so there is a bit more headroom for the regulator.

I have two units running using the uputronics LNA powered by the Nooelec NESDR SMArTee v2 SDR. Even though the SMArTee outputs 4.5v, it still powers the LNA without any issues. I have the LNA directly connected to the SMArTee via the SMA joiner. Almost 12 months now.

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I switched to Nooelectric LNAs because they can be powered directly via USB or bias tee. Because they are broadband, it is best to put a narrow filter in front of them.
ant → filter → lna → receiver

Good to know -thanks.
And welcome to the forum.

I have had REALLY good luck with this arrangement. I put the filter and LNA right at the antenna.

A challenge I am facing right now is that all the LNAs I can find are not outdoor rated. I am starting the process of trying to waterproof one, but my first attempt with Gorilla Waterproof Patch & Seal Spray did not go as well as I had pictured in my head. Instead of spraying like a spray paint, it was more like a wasp spray.

Anyone making LNAs that can go outside on the tower right under the antenna?

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they are expensive

Wow, those are expensive! The funny thing is, when I setup my first outdoor antenna back in 2015, I used some random in-line satellite TV amp I had laying around with the giant brick power supply and it’s worked amazing and is still trucking away. I am terrified to touch it!

I have been doing testing in my attic with several antennas, filters, and amps because I want to setup a dual 1090/978 system. I have had a little free time to finish up some fiddling and testing, and the amp is my final piece at the moment.

Try using an inverted 2 liter beverage bottle. I’ve cut a bottle to fit a camera inside, then resealed the bottle with waterproof tape. The power/data cables exit through a wine bottle cork at the cap end. So far I’ve not had no moisture issues in the wet Florida environment.

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