Linear power supply

Suffolk_guy61Suffolk_guy61
in Installation, Antennas and Interference

Hello


re powering the Kiwi, I am wondering if this linear power supply would be any better than the Apple 20w charger I am using at the moment.



Comments

  • G8JNJG8JNJ

    It depends...

    If the Apple charger is actually contributing noise in the first place, but it may not be.

    There are so many potential noise sources, in, and around the home, that it may not be possible to observe any difference if you swap out the Apple supply, as its contribution may be masked by other stronger sources.

    With noise, it's a bit like peeling an onion, as soon as you remove one layer of skin, there is another thinner layer underneath.

    Personally, I'd attempt to identify other noise sources first, and try and deal with them, and work your way through the increasingly diminishing returns.

    I use a TinySA Ultra with a telescopic antenna to "sniff" for noise sources around my property. But with care the KiWi can also be used for this purpose, by connecting a "sniffing" antenna via a long length of coax. Just be aware that when moving the antenna around, there is a short delay before received signals produce an output or appear on the waterfall.

    Regards,

    Martin

    F5AFY
  • Suffolk_guy61Suffolk_guy61

    Thank you for replying. I know I do have a lot of other RFI, but I have always read that linear power supplies are the 'quietest'.

  • G8JNJG8JNJ

    Linear supplies tend to be quieter than switched mode supplies. But they can generate some noise.

    The biggest problem is often that they can introduce an additional noise route via the mains earth, which may not happen with small switched mode units, as they tend to be double insulated, and their design reduces coupling between the mains and DC sides of the supply.

    At my Wessex remote hilltop site, I replaced all of the existing switched mode supplies feeding the sdr's and antenna distribution system with linear supplies, but it made very little difference to the (admittedly already very low) existing noise floor. But I did notice that the VLF noise floor increased slightly, due to the earth loop problem I previously described.

    Regards,

    Martin

  • Suffolk_guy61Suffolk_guy61

    I am going to make a mains filter which may or may not help, I don't have enough battery packs to run everything on batteries to see if it makes any difference. My noise floor is about S5 - 7, but is it caused by the mains or not ?

  • G8JNJG8JNJ

    No, a lot of the interference you have is being radiated by the noise source itself, and received via your antenna.

    I commented on the various ones I could identify in a previous thread.

    https://forum.kiwisdr.com/index.php?p=/discussion/3666

    Regards,

    Martin

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