XL6019 output to 5V radio

[zalves]

Hello Electronics Enthusiasts!

I'm 42 and recently embarked on my electronics journey. Currently, I'm enrolled in Andre LaMothe's Udemy course, which I find fantastic!

I've successfully assembled a DIY radio from Aliexpress. It operates well with excellent sensitivity tuning, and the audio quality is pretty good when connected to a proper speaker. The power input options are either 5v via microUSB or two AA batteries. Since I want to enhance the speaker setup, I plan to 3D print a new enclosure. My goal is to use the additional space to have 18650 batteries for power and include a USB-C port for charging.

In the process, I connected 18650 3S batteries with a BMS to an XL6019 to regulate the voltage to 5v, I connected the 5v output to where the microUSB input is. Unfortunately, this setup doesn't work as expected. The radio turns on but struggles to tune into any station, only producing noise. When directly connected to a bench supply with a 5v output, it functions perfectly.

I experimented by having the radio connected to the output of the XL6019 while simultaneously being connected to the bench supply (with its output turned off). Surprisingly, the radio received signals quite well, though not as efficiently as when connected solely to the bench supply or via its microUSB port.

I've conducted various measurements using a simple portable oscilloscope (DSO-TC3) and tested different capacitor values (10uf, 220uf, 470uf) between ground and 5v, thinking it might filter AC, but there was no noticeable change. I'm anticipating getting a better scope in a few weeks, but my current understanding limits my ability to grasp the underlying issue.

I'm eager to make it work with the 18650 batteries. Is there anything I can do to troubleshoot or improve the setup? Should I consider using something like an LM7805 and build my own voltage regulator, keeping in mind concerns about power efficiency?

I hope this clarifies the situation, and any guidance would be greatly appreciated.

[tunk]

Two new alkaline cells are around 3.2V, so one 18650 (or several in parallel) should work fine.

[wasedadoc]

The XL6019 is a switching regulator.  It will be chucking out a lot of RF which may be drowning out the wanted broadcasts.

[zalves]

I see maybe I can build a filter for it

[Jeff1946]

Look for modules using a TP4056A chip.  They have a USB socket on them.  They are specifically for single cell Li-ion batteries which must not be charged to more than 4.2V and also NOT discharged to less than 3.7V.  See https://www.addicore.com/products/tp4056-tc4056a-lithium-battery-charger-and-protection-module

[wasedadoc]

I see maybe I can build a filter for it

A filter is unlikely to help much. as the interference is radiated through the air whereas your filter will only tackle what is conducted along the wires.

If you have a long length of cable use it between the XL6019 and the radio so that you can greatly increase the distance between them and reduce the noise received by radiation.  If reception improves it proves the point and you will have learned something.

[Jwillis]

Try twisting the power wires. Loose wires act like broadcast antennas so twisting then acts like a common mode choke cancelling out the noise generated from the power supply.

[wasedadoc]

Try twisting the power wires. Loose wires act like broadcast antennas so twisting then acts like a common mode choke cancelling out the noise generated from the power supply.

That will not help if is the board itself that is radiating.

[radiolistener]

You're using DC/DC converter which produce a lot of noise, this is why your radio is flooded with noise.
You can reduce noise with using filter and more expensive better quality DC/DC.
But with using DC/DC you can't eliminate noise at all, some amount of noise still will be present.

DC/DC converters and radio are incompatible things 

Just use two 18650 in series (6.0-8.4 V) with LDO linear regulator for your radio and it will works ok.

[tunk]

If I found the correct schematics, the 5V input has an ams-1117-3.3
regulator. So it should be possible to connect a 2S battery directly to
the micro-USB. You could also see if it works with a single cell (1S).