PSU - identify the 34p one

Bit of a scam this as I'm not including the price of the supply before it but one of these three screen dumps is from a variable DC-DC 3A adapter that I purchased ten for less than £4

The other two are the stock 1500mah/5V switcher and a Linear PSU that cost me £80

The supply feeding the DC-DC is a 12V/1A BTW, linear type but nothing special.

When I see PSU noise it is normally down that end and the full spectrum didn't show much more. Yes I know that I live in a noisy place and sorry if the screen looks dark I use F-Lux and was trying to get this tested while my neighbour was out (very rare).


  • edited December 2018
    the middle appears to have the least noise.
    is this linear or switched ?
  • OK so you spotted the Linear.

    I checked if these DC-DC where still about the same price (Banggood not Ebay, Ebay are expensive now) and they are a bit more expensive, if someone has £10 they could afford 20 (£9.87 - mp1584en x20), sorry to mislead anyone by 15%!
    Also they may need a cap on the output or some other work as my Kwi did the "start but no network" thing which can happen if the voltage dips during boot.
  • I'm able to use an smps on my kiwi with no significant difference in noise level between that and a linear DC supply.
    this mainly has to do with the build quality of the smps being used.
    the smps I'm using is charger/DC supply for a 90's Sony camcorder I modified.
  • I'm sure there are many older supplies designed when compliance was "a thing", I've got a few that seem pretty good but I'm keen to find resonable current options for those people without decent "junk" reserves ;-).
    I hadn't tried these tiny PCB's simply as I had assumed the noise would be too intrusive but a comment on here prompted me to look. Linear supplies are getting harder to find more so considering switchers are often listed a "linear" now. In fact I'm getting annoyed with the amount of fake carp on Ebay, can't trust many listings now around power supplies, I still look for older stuff with full traceable approvals.
  • One thing that I have noticed can cause significant interference below 1 MHz is if the metal case of a KiwiSDR touches anything else - particularly another Kiwi: Clearly the result of a ground loop somewhere as sharing a common antenna ground and/or power supply between Kiwis doesn't seem to cause a problem.

  • My Kiwi is in a different case type (old alloy hard drive enclosure) with the receiver grounded through the SMA connectors only, that would be a different beast as the path to ground (via 9 meters of 10mm copper and two 3/8" rods of about 1.6m total) touching the case doesn't do much. I have spent a long (too long) time trying stuff here, not following text books just changing things incrementally. To save going over the issue again I'm in a small house (shed by US standards) with lots of other small houses close by, I'm the nutter who gets all exited about power cuts as I jump out of bed put the SDR's on and listen for what fires up as it comes back on. One new irritation is one neighbour must have run out of data on their network plan as I believe they have unplugged the VDSL modem and it tries to sync every twenty seconds, will have to knock on the door at the weekend, see if they will let me put some ferrite on the leads.
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