[hpsdr] Analog Vs. Switching power supply for OZY Janus...

[Neal Campbell]

Does anyone know the current requirement of the +-15v feed for the SDR1K? I
am interested in bypassing the chopper on mine but want to know how much
current it needs.


73
Neal

On 6/11/07, Tony Langdon <vk3jed at gmail.com> wrote:
>
> ***** High Performance Software Defined Radio Discussion List *****
>
> At 05:50 AM 6/12/2007, k5nwa wrote:
>
> >The problem I see with switchers is that although they could be made
> >quiet, many do so at different degrees of success, so buying one is
> >somewhat of a gamble unless someone else has had experience with the
> >particular model that one is interested in. With an analog supply on
> >the other hand, it's a non-issue.
>
> I'd agree switchers can be a gamble.  My experience with cheap
> computer switchers is they are highly variable, from quiet to
> noisy.  On the other hand, the 40A switchmode I use in one of my
> shacks is quiet as a church mouse.  One of the local hams actually
> disassembles his and found at least 5 separate stages of
> filtering.  On HF, there were some birdies that were barely
> detectable with no antenna on the radio.  When the antenna was
> connected, the HF noise floor swamped any noise from the power
> supply.  My experience is identical.
>
> OTOH, the difference in heat dissipated and the light weight of the
> power supply are readily apparent.  The supply powers a small
> repeater, and it's nice to not have to worry about how hot the thing
> is getting.  The previous linear supply used to have a 5" fan aimed
> at its heatsink to ensure proper cooling.
>
> Another subtle thing - a common failure mode of linear supplies is
> for the pass transistor to fail shorted, so you need a good crowbar
> to protect the radios.  Switchmode supplies most commonly fail with
> no output, so if it smokes, the radios have better odds (though like
> everything else, there is always the possibility of linear supplies
> failing dead and switchmode ones putting excessive voltages onto the
> supply rails, as anyone who's had computer parts fried by a wonky
> power supply can attest to.
>
>
> >Hopefully as people try out different models they will publish their
> >results so a list of good switchers can be compiled.
>
> Well, once a good switcher is identified, that's what I intend to go
> with for weight, space and power consumption reasons.  Just have to
> find a suitable one that's as quiet as the big bench
> supply.  Speaking of which, I've seen another 13.8V bench supply
> (switchmode) come onto the market - the other shack is likely to get
> one of those, and the linear supply retired to light duty elsewhere
> in the house. :)
>
> 73 de VK3JED
> http://vkradio.com
>
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