Please advise Pi4 2G

I have an input voltage of 5.25V and that gives me an output voltage of 5.1V on the USB3 port.

The USB3 (as well as USB2) standard allows for a maximum output of 5.25V, the Airspy seem to handle 5.1V without any problems.

The Pi4 uses a MxL7704 PMIC that can handle up to 5.5V input DC so it’s within limits as well.

Perhaps it will have some impact further down the road (more power → more heat) but so far it’s been working fine.

Actually this could be beneficial as the 5 V is basically never used directly.
Thus it’s stepped down and in certain limits this might give you more stable voltage rails.

But one always has to be careful and test with just the pi as the input voltage at the pi will be load dependent. (the power supply output will also be slightly load dependent)

Of the passive heatsink/case, there is the short and long versions.
Personally I prefer the ‘long’ case like this (it fully covers the connectors)

image
compared with the ‘short’ case
image

Unfortunately Reichelt no longer ship to the UK.
I wonder what caused that?

Obviously unreliable delivery. It happened also on some UK based companies that they do not deliver to EU.
My wife was waiting for some goods she purchased. Finally the package returned to the shop after pinging around for almost four weeks in the UK

I ordered my Uputronics from PiHut in the UK and was surprised getting it delivered in less than 24 hours. But i selected DHL Express for exact that reason

That’s why I went with a power supply with decent specs and reasonable price. I’ve had my fair share of problems due to cheap wall-warts (I’ve managed to produce a decent amount of magic smoke when using cheap, unregulated power supplies :grimacing: )

May be Brexit caused it? And a lot of extra (paper) work?

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Correct. Apart from the bias-tee which requires at least 4.8v VBUS, everything else can be run down to 3.9v. Anything over this voltage is converted to heat. The actual radio circuits operate at 3.3v. The low noise voltage regulator require 0.3v extra voltage for its own biasing.

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Sorry I was being sarcastic.
I suspect talking politics probably isn’t approved of on this group.

Airsspy can handle that low of a USB voltage?
Didn’t know that.

Anyhow i was talking about the RPi mainly which is using buck converters which might even work better with 5.1 V instead of 5.0 V.

No worries, nobody blames you : :wink: Some of the members are even more sarcastic

So if I don’t use the built-in bias-tee it’s possible to drop the voltage down to 3.9V for the mini?
If possible it would be interesting to see if that affects the signal processing in a positive way. Less heat should be a good thing?

Umm … certainly not my experience.

Do you mean “low dropout regulator”? (rather than Low Noise Reg.)
Most RTL dongles use a LM1117-33 (or one of many clones - AMS etc.)

Ti spec their reg at 1.15V min. dropout (@ 0.5A load). so the min input is 4.45V to the dongle.
Unless you are using a powered hub, the Pi will also cause a voltage drop meaning you have very little headroom below 5V before the dongle starts to suffer.
image
I agree with @wiedehopf that 5.1V is more reliable than 5.0V on the input to the Pi.

@prog @wiedehopf - sorry if I’m being a bit slow.

If the Airspy Mini is relatively insensitive to low voltages, why does MLAT fall over if you try feeding it with long/thin USB cables? I thought that it was an under voltage issue.

Both the MCU and the tuner run at 3.3v.

Your computer will suffer from undervoltage before the SDR. Of course, if you use a cable of terrible quality, you walk into other USB signaling issues. The lower voltage arriving to the unit is a secondary symptom.

We use Low Noise RF LDOs with 80dB of rail noise rejection - for obvious reasons. It’s a radio after all.

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Last weekend I got my Pi4 with a Armor Case with fan.

Thank you all for the help!!!

I am very pleased with it, as the temperature dropped form an average 62C to 39.4 C! And besides that as said in the previous posts, the fan is running 25/7 and even during the night it does not disturb our night rest!

And I also got my Airspy mini!

Still looking for the best settings after installing Wiedehopf’s script for the Airspy, but it looks promising.
I never saw a message rate > 1220 and today I saw even >1600, just a few more, but it is an improvement of 30%!

I set the gain on 19, but the weakest signal is -24 and I do not have any single messages, so I assume i have to play with the gain to get the weakest signal to -30.

I also see a few planes more somewhat further away. Some even over the Heywhatsthat lines. The total planes has not improved that much, but it still the beginning :wink:

All comments and advice is highly appreciated

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I have the same situation and was setting the gain to 18 at the beginning, later to 19.
There is no significant impact. only if you want something on the max range, but i would count this as standard deviation.

As far as i understand the Airspy is very tolerant as long as you are not using extreme value changes.

You can see the change from 18 to 19 at around 11am

Thank you for the fast comment.

IF…I remember well said Wiedhopf in another thread the his advice is weakest signal around -30
So I will have to figure how to achieve that.
In my ADS-B tracks seen, I don’t see any single message. In my previous settings I had always single messages. Is that “normal” for a system with an Airspy Mini?

They are still there but not that many:

Try and Error. Simply let each run for a day or so and then decide
If i understood @wiedehopf correct, it’s a personal thing what you want to set up.

Already decided to do that :wink:
Was just curious about the single messages.