Checking DC/DC Step Down Converter for Spectral Purity

I just finished a video where I use a Tiny SA to check the output of various transceivers when powered by a switching DC/DC voltage regulator:

Please let me know if I missed anything or can improve my method.
73 de OE6FEG


Interesting, thank you.

I used a DC/DC Step Down Converter when I started using 4S LiPo’s for SOTA.

With the particular model I happened to have available at the time, I noticed a significant increase of the received QRM. Since then I use diodes in series to drop the voltage when the batteries are fully charged (cheap, light and reliable).

It is interesting to see that transmit spectral purity does not appear to be affected, but for SOTA activations, I would recommend checking if the reception is not impacted on the bands of interest with the particular model of DC converter one intends to use.


Unfortunately the EMC of DC-DC converters varies widely depending on the design (and cost). I have seen ones that were generating RFI from LF to VHF, and another that was perfectly clean as far as I could tell.

CE marking is no guarantee - as with other products I have seen marked units with spaces on the PCB for suppression components - which were then omitted !

Also have you heard of the “China Export” problem ? They have created a logo which looks just like CE but isn’t - see here

The only way to know is to do your own testing - which is is exactly what you did :slight_smile:


RX is clean as well; that is a prerequisite for any DC/DC converter I use.

  73 Matt
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Urban myth. They are simply poorly rendered CE marks, and of course, not valid.

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Could be - I’m perfectly prepared to believe they will stamp anything on anything - whatever the customer wants …


Yep, debunked by the European Commission.

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