VK6KCH
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Allow DRM to preempt autorun FT-8 and autorun WSPR [fixed in v1.806]
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Quiet switch mode power supply (SMPS) for KiwiSDR
As part of cleaning up the RF environment at my QTH, I ran a quick Apples-vs-Apples comparison on two switchmode power supplies.
At least down at the VLF part of the spectrum, the newer Apple A1444 power supply (the compact little brick without the ability to change the 230V pins) is significantly quieter than the older Apple A1205 SMPS (the one that allows you to swap out the 230V connector when you're roaming to another country, etc).
The image below shows the cleaner spectrum of the A1444 below, versus the slightly noisier performance when powered from the A1205. Nothing else was changed, and the comparison was made just a few minutes apart, and then re-confirmed back the other way a few minutes later.
At a subjective level, it was much easier to copy the Pearce NDB on 340kHz when using the A1444 SMPS, versus the NDB being detectable but virtually unreadable on the older unit.
[ 281kHz and 340kHz are the YPJT and YPEA NDBs, whereas 158, 238, 316, 397, 476kHz are noise coming from source(s) that I'm yet to find and mitigate. I suspect they are coming from other SMPS ]
Of course, this is just from a sample size of one, but I thought I'd share this observation in case it helps anyone else.
73, Chris VK6KCH

