FlightAware Discussions

Pi Aware Power Source - effects reception why?

Hi all,

I recently changed the way I am powering my raspberry pi and noticed that my reception /number of planes per day dropped significantly. (about in 1/2)

I have a Raspberry pi 4 running Pi Aware running off a 12 v solar system & battery bank.
I initially had a small 150 watt inverter powering a standard pi power brick it consumed ~200 watts per day (12 volt -> 110 v ->5)

So I changed it to run off a buck converter 12 v -> 5 v (100 watts per day) directly to pin 2 & 6

I used a usb power monitor between the pi and pi aware dongle and made sure both setups were feeding ~5.14 v .26 amps .

I am looking for any thoughts on what is going on? or better yet what I am missing between the two configurations. any guidance would be appreciated


One of these units is not correct :wink:

Check if the Pi itself thinks it is seeing undervoltage.
Other than that - different RF noise environments?

I assume he means Wh, not only W

My device is connected to a managed power unit which can measure the power used.

This is the result the last 30 days, it shows approx 0,15kWh per day:

An 12V->110V inverter will have it’s owns standby current (not insigificatn) and you get losses both going up in voltage and going down.
Using just a buck converter is a much better setup in regards to power usage.

Anyone thought about noise from supply being injected down wire to Pi?


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Yes it should have been Wh,
Is there a filter to reduce/remove the noise that you would recommend trying?

If this is the case I am surprised that the buck convert has more noise than the inverter, or is noise a good thing?

The buck converter specs says it draws 25mA,

I have several other types of buck converters that I can try and see if that changes anything

here are some pics of my setup (for context):

this is the solar setup, the Pi is to the left on the white shelf

this is the inverter:

here is the pi with buck converter and USB power meter between Pi and USB dongle:

No it’s not.
If you had graphs1090 that would be quite helpful as it provides some more data.

The buck converter in contrast to the intverter will mean you have a common ground between your pi / coax and your 12 V power source.
I suppose that could cause issues in some situations if the grounding for the coax or antenna at some point meets again with the 12 V ground.

You can certainly try cleaning up the power.
If you’re into more technical stuff.

Put some capacitor across the in and output of the buck converter, also put a choke in series with the input and output.
That would probably reduce noise.
I don’t have that much experience with that but the article suggest filtering in and output of the buck converter for some reason, i suppose it makes sense.
I’m sure you can find more info on which values might be sensible or you can just have a look at some old power supply that’s no longer working and just grab some random components that are rated for the voltage (capacitors) or seem beefy enough (coils).

I recently installed a Mean Well LRS-35-5 PSU that powers my RPi4 and the external Bias-T injector. I’ve set it to 5.2V to make sure that I get 5V on the USB3-port I’m using for the Airspy R2.

It didn’t make the reception worse, probably a little better, but since I did that at the same time as I exchanged my Airspy mini for the R2 I really can’t tell if the PSU or the R2 made the difference.

Thought about a buck converter, but this was a better solution for me.

So I tried a couple of things, quick update:

  1. I used a different inverter (300 watt) and the flight count went back up :slight_smile:
  2. I used a second buck converter, it does not have a display so I preset the output to 5.1 volts, the pi would not start so I turned the pot until it did and when it came on i noticed that the flight count was up but not maybe as high as the inverter (but hard to tell), I check the output voltage and it was high (6.03v - after checking a couple of sites they suggested that I could possibly push the to 6.00 volts not more) I’ll back it off to 5.9 and see how long it lives :expressionless:
  3. I ordered a USB-C terminal block that i am going to connect to the buck converter at 5.25 volts, I will see if powering the pi thorough the USB C port rather than over the GPIO will have any effect,
  4. I also want to measure what the USB C power brick is feeding the pi so I purchased a USB C power monitor similar to the usb a one I have now.

I will also install the graphs1090 software for better data logging

If EMI is a problem for that setup, then a switching power supply of any sort would not be the proper avenue to take. I have one just like and while it works very well, it’s not really good for RF sensitive setups.

I agree, that’s probably the simplest/cheapest method to try first to see if it clears anything up. I’ve had quite a few home-made breadboard glitcher setups and that worked the best coming off the buck. Breadboards and up being huge antenna anyhow, but using caps can really tone things down so far as EMI. Not that anyone here is using breadboards for any of this, but the same principle applies.

I have some 1nF capacitors lying around, are they big enough, also " I have never used a choke what is a good size/spec. I am using a RadarBox 1090 mhm antenna with a 10m cable.

One trick I have used is a small AM radio and snoop around the components to look for noise. Your setup maybe too compact to different between noise sources but worth a try.

Was looking for linear PSU’s but locally sourced ones where a bit too expensive, and I suspect that even if I got one, the RPi itself generates noise enough to cause issues. My issue were temporary drops in the +5V line on the USB port and the Mean Well PSU is easy enough to adjust and can supply a reasonably clean voltage. EMI was not the main goal, it may be something I look into in the future, but then I may use something else than a RPi.

That’s their huge drawback - expensive, usually clunky and suck at efficiency as a rule of thumb. Linear is not a necessary for our setups as many probably run with full Bluetooth/Wifi anyhow. USB has its own noise as does HDMI, so it’s sort of a losing battle however you add it up. I always shut the wifi/bt/hdmi off in my setups, but we live in loud environments and spending a ton of money to capture a couple more planes or messages a day is futility. That said some are perfectionists and it’s sometimes worth the conversation, especially since the OP is evidently experiencing such EMI issues.

Another way to quiet the power side of things down is to run from battery. Yet another expense and chain of supplies to get and add to the complexity, but it can be fun to experiment and tinker which is why many (most?) of us hang around here anyway I think.

ADD: Speaking of battery. I just ran some tests on one of my Pi4’s setup to boot directly from a USB stick, overclocked to 2Ghz, running an Argon Fan Hat with an Airspy Mini running 20MSPS, while running a sysbench test maxing out all 4 cores, the lowest voltage I seen from the below unit was 5.19v @ 1.58A:

The above is one of the more rare battery packs that you can buy that supports passthrough charging (IE plugged into the wall while being used). I have a few others, but all of them immediately dropped to about 4.8v or so under the same conditions. To make sure this wasn’t a fluke, I grabbed another identical battery pack from my other son and it tested the same. I also stuck my load tester on the 2nd port while running the sysbench and I was able to keep it above 5.17v @ 1.5a simultaneously.

This may be a good alternative for those looking to run clean power as it doesn’t get more linear than battery. Another advantage is that using something like this will provide you with around 12-14 hours of run-time should the power go out. :slight_smile:

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That inverter puts out power with a modified sine wave. It delivers power via 2 or more turning blocks above and below zero. MSW peak voltage may stay instantaneous for a few milliseconds, and at the zero cross, voltage can be zero for a few milliseconds. I’d suggest trying a pure sine wave inverter; they’re more expensive but they cooperate better with sensitive electronics.

I’ve disabled HDMI, wifi and BT on my setup, but my house is filled with LED-lights, plasma TV’s, computers, wall-warts of various quality and a couple of routers/access points. A faraday cage for the RPi is probably the only way to address the EMI issue. The sheer amount of electronics in the house makes it very hard to have a EMI-friendly environment.
I may have to convert the old pigsty I have to a large faraday cage and build a 30m mast next to it :laughing:

That may be a possible route to take to get clean power. The power bank you have looks interesting.