The one on the right is a bias-t. I have the same one.
One LNA, one bias-tee injector.
But the Airspy mini can work in Bias-tee to ?
It can, but the spec for that is 50mA maximum. The rtl-sdr.com LNA draws more than that.
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If i understood prog correctly, the 50 mA limit is to comply with the 500 mA USB limit, not really an airspy limitation.
But USB power is limited anyway and it sure doesn’t hurt to use an extra bias-t.
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thanks for the anwsers ;+)
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I’ve seen that posted before. I don’t actually know what the safe limit is likely to be however since it’s not posted anywhere explicitly - I noticed that my airspy got rather hot when using the internal bias-t so the external one seemed like a good idea.
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And this is mine in the attic, I couldn’t wait for bias-T to arrive so I drilled a small hole in the LNA to provide 5V soldered directly to the pcb.
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I’m using the bias-t of my Airspy mini with my Uptronic LNA, do you think that is wrong, and better to use the USB power of the Uptronic ?
The uputronics lna need less power, so that should not be a problem.
Giving the Airspy mini some passive cooling or adding a fan doesn’t hurt, no matter how you use it.
But it should work fine as is.
Thanks for the reply !
My system is in the garage, so actually no heating problem ;+)
And the Airspy Mini is less hot than my previous key Nano 3 !
That cold in the garage?
Anyway small heatsinks with tape adhesive are really cheap.
Your Pi4 will also get quite hot, this one would probably cool the airspy as well: Fan SHIM for Raspberry Pi
But if the garage never gets above 30 C it’s probably not necessary. Not sure though with the Pi4, it seems to run really hot, and you can’t have throttling kick in.
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For my Pi '3 and 4) i’m using this : https://www.amazon.fr/gp/product/B07V7FQ5LS/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
For example this summer my Pi3B+ with a standart case was at 75°C, and with this case no more than 45°C !
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keithma, I have almost the same hardware as you, and I struggle with the gain adjustment !
In the end what is the gain value you have retained for you, to give me a starting idea for my tests ?
I know that this value will not necessarily be good for me, because we are not in the same place, but it helps me to understand, especially with your graphs, I can directly compare with my settings ; +)
Thanks !
It’s not really critical with the Airspy.
Try 15 to 19 in combination with the rtl-sdr LNA.
Probably all of the above gain settings will work equally well.
I’m running gain at 14 and as I said, I haven’t adjusted it since raising the aerial. Over a few days testing, I found 14 was the optimal for me when it first went up.
Thanks guys for the reply !
With my test and differents gains settings i obtain this maximum :
- Uptronics Ceramic model powered by the AirSpy Mini : 1650 Messages / s
- RTL-SDR LNA powered by the AirSpy Mini : 1100 Messages / s
Do really need a separated Bias-T for the RTL-SDR LNA ?
The Uptronic model will be better with an USB power supply instead the power supply of the AirSpy Mini ?
Near my location (30/50 Kms) i have many differents littles airports, with little trafic like Cesna 172 or Robin DR400, but at maximum i seen only 2 or 3 planes like this, is it beceause my gain is too high ?
Thanks.
P.S. : Sorry if I polish your topic, in this case tell me and I would put my message elsewhere.
Create a topic 
Test a day with each, i’d be curious about the resulting graphs.
Maybe test with a gain of 14 for both?
Depends how high those planes fly and if they have an ADS-B transponder.
MLAT only works if at least 4 stations receive the plane which is always difficult with low flying planes.
You can try just lowering the gain. (GitHub - wiedehopf/airspy-conf: Configure airspy_adsb for use with readsb or piaware.)
Did you already switch to the Pi4?