USB-C as a KiwiSDR Power Source?

I am routinely powering my Perseus and Cloud-IQ SDRs from USB 3.0 ports of my PCs. This introduces no extra noise, compared to a linear PSU. Running a KiwiSDR off a 3.0 port is not possible, but I understand that the new (or not so new) USB Type C will allow 1.5A. So, my question is: Has anyone tried?


  • I have found the Kiwi running takes about 720mah here (5.V) I think that is possible on USB desktop ports of most versions (pretty sure 1A on desktops -500ma on laptops) but I'm not so sure about the requirement while booting.
    They do seem to like a good solid 5.0-5.2V to cleanly boot, if your USB ports are like mine they seem to idle at 4.9V and then ramp up to suit the load (if this little Chinese usb in-line meter is accurate).
    If they current limit while booting that would not be a good scenario.
    You could do what they used to with spinning hard enclosures for laptops and have a two port cable (one was data and one just power). I think I did try from an extension cable with powered USB 2/3 ports on, that was noisy.

    I've not tried to a PC but I would be quite surprised if doing that doesn't introduce some noise, would be happy to find out I'm wrong.
  • 720 mAh? Are you sure? I believe the specs say >1Ah, and I haven't been able to start up the Kiwi with a 1A PSU, or with a USB 3.0 (typically 950 mA) port.
    Yes, voltage is a concern. All USB 3.0 ports on my PCs are 5.02 to 5.04 VDC (measured with two different DVMs). My current PSU is running just south of 5.2VDC as per John's advice.
    As for noise, I did a write-up some time ago, link here. Of course this is anecdotal evidence only, but at least it shows that you can power your SDR from a PC.
  • edited November 2018
    I ran two on the same Linear PSU, the built meter read 1440mA or thereabouts, I left it at the lowest it would go *(Nobsound 25W USB DC5V-24V Adjustable).
    Checked it yesterday and one Kiwi SDR with a TP-Link mini wifi on the same supply was ~925mA
    I have run one Kiwi and a RouterBOARD 941-2nD off the original 1.5A switcher without any issues.
    I think Martin on here said his Kiwi was even less so I assume it is in the right area (maybe he has a more accurate current meter).

    As I said "running", I could take one to work and look at the current draw on start (digital scope) if it became that critical.
    I do believe there is a rule something like - complete guess- "must not dip below 4.95V during boot" linear supplies with decent caps seem to be a good move but even they should not start near the trip point.

    I'll look at your PSU post later, too much to read in a work tea break.

    *please note I'm not recommending that PSU, it's just what I'm trying right now, the improvement over the orginal switcher was not as much as I was hoping for and I really need to disconnect the fan as I'm not running it hard and the thing is bit noisy (small fast fan) I do like the display though, not 100% sure if that creates any RF noise.

  • Would it be possible to 'buffer' the USB port with something like a rechargeable power bank ?

    PC to charge port on power bank and 5v output to KiWi ?

    When I checked one of mine the other day with a cheap DVM, it was drawing about 600mA, but it could easily be peaking much higher than that for short duration periods.

    I find I have to run at about 5.4v into the KiWi to get 5.0v at the Beagle. The KiWi also provides a common mode choke and RF filter capacitors on the DC in socket.

    I'm not sure what voltage you would require if you powered it directly via the USB socket.


    Martin - G8JNJ
  • Kiwi starup inrush is high but the run-time power is < 1 amp.
  • edited December 2018
    As a bit of follow up on the PSU I mentioned above (Nobsound 25W USB DC5V-24V Adjustable).
    I have found it is potentially dangerous as delivered to me.

    I was going to look how easy it was to disconnect the small fast fan as that is the biggest drawback with this PSU, it's a bit noisy. I started dissembling it and spotted a mark on the top metal cover where the centre bolt of the toroidial transformer mount was hitting the top cover, I know that is a bad idea as it creates a shorted turn through the case so then I looked at how I would take it apart to cleanly cut the bolt without leaving swarf in the PSU. The connection from the mains inlet earth goes via a tiny wire to a M2.5 screw through the back panel (Anodised) long story short there was no continuity between earth and the chassis.

    A couple hours later (lol) I had cut the centre bolt down and made new earthing connections to upper, lower covers and back panel (front panel is plastic).

    Not brilliant but I feel happier handling the thing now.
    I forgive some Chinese stuff as it is often really cheap but this was about £80, just poor IMO.
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