FlightAware Discussions

RTL-SDR LNA Install

I was just wondering if it was ok just put an adapter to the bottom of an AF antenna and then add the bias tee right before the NooElec USB stick. I’ve got both a 3.5v and 5v transformers to try.

Some thing like this. Pls ignore the morning dew on the antenna base. The connection is dry and this is just to show how I’d like to install it.

On a side note, does anyone have a pic of the LNA disassembled? I’d like to confirm mine is correct to the in and out labels.

Thanks!

That’s a good way to install it if you manage to weatherproof the LNA.

Especially with your problems i would try and get it running indoors first.
As i wrote earlier it should be at least as good as before.
There have been defective units shipped, usually it’s not a problem to get a replacement.

They have a picture on the product page: https://www.rtl-sdr.com/new-product-rtl-sdr-blog-1090-mhz-ads-b-lna/

image

Note that on this picture the right side goes to the antenna.
The left side goes to the bias-t.

Thanks again for the reply.

I tried 3 different bias tees 3.5, 4.5 and 5 volt indoors and I get no more then about 30 nm. I’m going to guess the LNA is defective.

What is that adapter between the bias-t and the LNA for?

I didn’t have another small sma2sma(like between the bias tee and the nooelrc) so I just used the ones I had at the antenna to connect the LNA and bias tee for testing.

It does indeed seem to be the case.
Hopefully delivery of the replacement isn’t gonna take too long :wink:

I remembered there was some discussion about 50 ohm and 75 ohm connectors. The centre pin is a different size so you can’t mix them. Maybe your problem?

https://discussions.flightaware.com/t/strange-problem-with-my-fa-antenna-installation/20418/5

You could probably test the above by integrating it into the signal chain without inluding the LNA.

Maybe
cable – bias-t – big sma male to male – receiver

Don’t think it’s likely but it’s worth testing.

Too many amplifiers.

@Dxista had a similar setup running a Prostick+ after the rtl-sdr LNA.
It had a low message rate but not low range.

Second amp might be saturated. The FA dongle doesn’t have that high of a gain.

There’s a small green LED on the pcb that should be brightly lit when there’s 5V present.
I’ve modified mine so it has a USB cable soldered directly to the pcb, that way there’s no need for a bias-T circuit.

The first preamp is not receiving power; T-Bias doesn’t get power from the other preamp input.

That’s a bias-t.

At least that’s what was written.

I’m actually starting to doubt the bias tee now too. It may in fact just be a wide band amplifier. Trusting in my google search might have been a bad idea. I have since ordered a bias tee that you had linked to. Should be here in a month from China. :smiley:

Edit: misunderstood.

I ordered two different ones. I believe this is one.

and this is the other.

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What the *?

Those are both amplifiers, not bias tees.

Yeah, I understand that now. I googled bias tee and these are what came up. I’m still learning. :frowning:

Mostly with your help and the help of others here.

See… my sharp eye is confirmed :smiley:

So you didn’t get born with all this knowledge, like the rest of us? LOL

This is why this is a hobby, we all lean from each other here.

For now you can take out the preamp that has no power connected to it, see what results you get.

Alternately you can solder a wire between the positive pads of the preamps (just one because the negative is already connected between them with the shielded cables), but my hunch is that is not needed.