Topband: ROKU 3 QRM

[Paul Christensen]

>" from a 12V battery that is floated by a small linear supply. (A year or
so ago, I went through my home and got rid of all the switch-mode crap).

At last count, I have more than a dozen linear supply replacements here. 
Some are built into consumer A/V equipment, others are used to power 
routers, Ethernet switches, cell phones, etc.   I like the PowerOne, Condor, 
and International Power branded open frame "OEM" supplies.  I grab extras 
any time they come available on the surplus market - and often for well 
under new prices from Mouser and Newark.

Tackling EMI is always a maddening exercise here.  If there's the slightest 
noise bump on a panadapter display, I can't rest until it's gone.   Just 
this morning, I replaced what I thought was a quiet Toshiba laptop supply. 
It was being used to power a low-power SDR transceiver.  All was fine until 
I ventured down to the middle of the AMBC band this morning.   The grunge 
level increased over 30 dB when compared to 160m.

Paul, W9AC