[RFI] Anyone know if this 12v ps is RFI-clean?

[Roger (K8RI)]

On 11/6/2010 12:31 PM, Dale Svetanoff wrote:
> Doc,
>
> I've said it before and I'll say it again:  unless a power supply is
> designated specifically for communications applications, assume that it is
> NOT "clean enough" for communications usage.
I purchased a 40A lab supply at a very good price, (one Doc mentioned 
earlier) with digital read out it took a bit of testing but it turned 
out to be well regulated, and clean. Which BTW is also a switching 
supply.    Those big "conventional" supplies run just about a pound per amp.
The specifications for the PS will tell the story. There are many good 
switching supplies out there, and there are a lot more that are not 
suitable, but when you get ripple and noise figures in the 0.1% they are 
likely pretty good.

73

Roger (K8RI)
>   The unit in question is
> almost surely a switcher, and if intended for commercial applications, it
> will only meet FCC Part 15 Class A emission specs, which are several dB
> worse (higher) than the Class B requirements for computers and digital
> equipment used in the home.  (Note that the seller is including shipping in
> the $50 price - that tells me that the unit is light weight, virtually
> guaranteeing it to be a switcher.)
>
> For truly "clean" power, get a "hernia-maker" - meaning a linear power
> supply, not a switcher.  You only have to worry about 60 or 120 Hz hum and
> ripple with those.  If you don't want big iron like that, then stick with
> the select group of switchers that are designed for communications
> applications.  Those units will exceed performance of FCC Class B equipment
> by controlling both the radiated and conducted emissions.  Yes, you will
> pay more, but you get what you pay for.
>
> If you watch closely, there are surplus equipment dealers (and people at
> hamfests) who sell off big linear power supplies very cheaply.  They were
> the norm 20 or 30 years ago, and you can probably get one for under $50.
> You'll want to find it locally, however, as these babies usually weigh 40
> pounds or more when you start talking 50 amps (or greater) output current.
> Unless malfunctioning, they usually deliver clean power to the loads.
>
> 73, Dale
> WA9ENA
>
>
>> [Original Message]
>> From: doc at kd4e.com<doc at kd4e.com>
>> To: RFI List<rfi at contesting.com>
>> Date: 11/5/2010 9:35:04
>> Subject: [RFI] Anyone know if this 12v ps is RFI-clean?
>>
>> Anyone know if this 12v ps is RFI-clean?
>>
>> "12 Volt 47 Amp Power supplies"
>>
>> See picture here:
>> http://swap.qth.com/view_ad.php?counter=866425
>>
>> It looks like some sort of modified surplus server PS.
>>
>> I have asked the seller a couple of times but no clear
>> answer yet.  Does it look familiar to anyone?
>>
>> -- 
>>
>> Thanks!&  73, doc, KD4E
>> http://KD4E.com
>> Have an http://ultrafidian.com day
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