[aprssig] Persistent EMI/RFI Problem Solved (Stephen H. Smith)
g8kbvdave at googlemail.com
Mon Mar 14 13:48:10 EDT 2016
Hate to say it, but leaving a SMPS idling with no output load is asking
for trouble, and almost guaranteed to cause such odd EMI issues. Even,
if the same SMPS is clean(ish) when working into a load (check it just
The difference in radiated/conducted EMI between continuous and
discontinuous conduction modes, combined with it's controller no doubt
seeing over voltage events at the output so cycling the converter on/off
in a random way.
You might find an improvement by aggressively filtering the input to the
converter, but the only cure is to power it down when not used.
This is a common problem, especially with AC powered (wall wart) battery
chargers for things like power tools and golf trolley’s, invalid carts etc.
And don’t get me started about low voltage LED lighting! You'll be
amazed at how far up the spectrum the EMI from that technology spreads
Especially a problem, when the original high current electronic
"Ballast" has not been replaced with one more suited to the much lower
currents the LED's use. Again, SMPS's working outside their intended
operational mode, as a result, any EMI mitigation filtering is often
Lastly, always go EMI hunting with a mk1 AM RX. Unless it's a clean
carrier, then SSB/CW mode is the order of the day.
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