FlightAware Discussions

How do I know if I need gain adjustment or a pre-amp?

Hi all

I’m not new to flighttracking but definitely new to understanding how gain and pre-amping works. I currently have the official antenna, cable, orange stick and the 1090mhz filter connected to my Pi and I get good results but I want more. The problem is I don’t really know if I need to adjust gain or get a pre-amp to get better results… How can I find this out? I have the performance charts installed on my Piaware so I can always add those if they’re any help to working this out?

dump1090-localhost-signal-24h

Did you see this thread?

I think in this case another thread is even more appropriate: What is the Maximum Range I can Get?

A preamp you can often install closer to the antenna which can help.
Also the preamps generally used have very good filtering.
I favorite this one:

https://github.com/wiedehopf/adsb-wiki/wiki/Useful-items-for-purchase#highly-recommended-combination-of-lna--dongle

But considering you already have good range, i doubt you’ll get too much improvement.

Then you can also get an Airspy Mini in addition to the preamp.
But that improvement is mostly message rate, not necessarily range.

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Would the Airspy mini replace my current flightaware dongle? And how do I go about powering the preamp using my current setup? Do I need to add anything other than the cable and preamp?

external bias-t or bias-t integrated into the dongle.
(that’s why in the recommended combination the sdr has an always on bias-t)

Please note that this LNA requires bias tee power to work. Bias tee power is when the DC power comes through the coax cable. The RTL-SDR V3 has bias tee power built into it and this can be activated in software. See the V3 users guide for information on how to activate it. Alternatively if you don’t own a dongle with bias tee built in, then an external bias tee can be used and those can be found fairly cheaply on eBay.

From https://www.rtl-sdr.com/new-product-rtl-sdr-blog-1090-mhz-ads-b-lna/

Also it doesn’t really work with the Flightaware dongles as they already have their own amplifier, it results in too much amplification.

Sorry I am really stupid with this stuff so just allow me to just put this out so I can be sure I understand…

So External Bias-T and Bias-T is integrated into the dongle, whether it be the flightaware dongle or the Airspy mini? I take it it’s just a matter of getting the correct setting for this.

So if I was to buy the LNA, add this under my antenna with the pigtail connector, run the cable from the antenna to the 1090mhz filter and then buy the Airspy mini and add this in next, straight into the Piaware, are we saying job done?

I am reading the link as well but I just want to be sure I fully understand as some of this stuff is, I admit, much beyond my current understanding!

Appreciate the help so far guys, to note, i did adjust gain using a script from one of the links and I do appear to be getting more messages!

Then look up what a bias-t is.

And no not every dongle has a bias-t.
The Flightaware dongles don’t have a bias-t.

And as i already wrote, the Flightaware dongles don’t work well with the rtl-sdr LNA, it’s too much amplification because the FA dongles have their own integrated amplifier.

That is why i was asking about it with the Airspy rather than the Flightaware, I was saying I would replace it.

First it doesn’t need additional filtering and i’m pretty sure the filter would block the DC required to supply the LNA with power.

Second calling the Raspberry Pi a piaware is all kinds of confusing, it sounded to me like you would replace the dongle at a later point in time.

No matter, you can indeed power the LNA with the Airspy via the coax.
But the airspy needs some configuration to work with piaware, it’s not really a problem though:
HOWTO: Airspy mini and Airspy R2: Piaware / dump1090-fa configuration

With the bias-t powering this particular LNA, the airspy draws quite a bit of USB current, which can be a bottleneck.
Thus i prefer powering this LNA with an external bias-t.
Also means i can reduce the feed voltage to 3.5 V with a 20 Ohm resistor using the 5 V from the Pi. That way the LNA runs a good bit cooler.
If you have a rather long cable run between bias-t and antenna i’d probably only use 10 Ohms or so.

Ok thank you for that. I think I may instead get the sdrplay RSP-1a as it’s made in the country I am from therefore easier to buy than the Airspy.

My setup would then be something like this I suppose

Flightaware official antenna
Pigtail to LNA
LNA
BIAS-T
Cable
(remove the 1090mhz filter)
RSP1A
Raspberry Pi

I’m not sure that this device provides any advantage over an rtl-sdr compatible stick.
Also i don’t know if there is even an ADS-B decoder application available for it.

The airspy has custom software for decoding ADS-B using oversampling.

Just get a non-amplified rtl-sdr compatible SDR.
Both the NooElec SmarTee and the rtl-sdr blog v3 stick have an bias-t built in.

Also i think you mixed the cable and the bias-t in your list above, unless you fancy running power to the antenna.

Ok, I’ll rearrange that list. Would there actually be any benefit for me to do this if I am already reducing gain? I dropped it down and I now get more messages so I’m not sure I’d benefit

It’s hard to say how much better your reception would be.

Having the LNA at the antenna is a real advantage if you have a long cable run >15 ft.
Also depends on the quality of the coax, the worse the coax, the more advantage an LNA at the antenna gives.

Also the filtering of the mentioned LNA is very good.
But if that is an advantage for your setup is hard to say.

Basically no way to check either except try the modified setup.

Make your ADS-B life easier and more pleasurable:

FA antenna > RTL-SDR Blog LNA > RTL-SDR Blog v3 stick (see edit) > Rpi3

The lowest priced combination, with the best performance.

I had an RSP1A, while it’s the best value around in wideband SDR, it’s not the best option for ADS-B, in addition to being more expensive than other better options.

Edit: If you are not into fiddling with software or installing an external bias-T, get the NooElec SmarTee stick instead of the RTL-SDR Blog v3 stick.

Thanks for that, it would definitely be simpler but I do wonder if it would be any better than what I have, I guess there’s no way of knowing without buying it, I may end up grabbing those 2 bits next month as I have a spare colinear and Pi ready to go so I can run 2 side by side (though obviously the aerials are different)