[Amps] Switching Power Supplies

[Will Matney]

Correct, I did mean Steve. Sorry about that.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 7/14/06 at 3:36 PM Tony King - W4ZT wrote:

>I think this was meant for Steve ;)
>
>Will Matney wrote:
>> Tony,
>> 
>> What is the waveform coming out? Is it a square wave, or is it a
>> modified sine wave (a stair steeped square wave that supposed to
>> mimick a sine wave)? If it were me, I'd want the square wave, rectify
>> it, and then filter it well. All older modile tube amps worked this
>> way, so did automotive radios that used a vibrator, and later semis
>> to switch with. One needs to rectify it first, then filter it
>> thoroughly the same as any other supply. In your case you'd probably
>> be using a choke instead of a transformer, or will you be switching a
>> transformer? There's several ways to set these up. In any instance,
>> the weight savings is due to using a higher frequency.
>> 
>> Best,
>> 
>> Will
>> 
>> *********** REPLY SEPARATOR  ***********
>> 
>> On 7/14/06 at 2:56 PM Tony King - W4ZT wrote:
>> 
>>> Tom W8JI wrote: <snip>
>>>> I can't imagine why an amateur would want to use a switching
>>>> supply for a filament. What reason is there to do that?
>>>> 
>>>> 73 Tom
>>> Tom,
>>> 
>>> The reason I chose a small switcher for my filament supply was to 
>>> provide a stable DC filament voltage over changing input line
>>> voltages. The switcher I found was a fully shielded commercial
>>> variety that appears to be relatively RFI free, weighs less than
>>> the transformer normally used and generates none of the heat an
>>> analog regulator produces.
>>> 
>>> My experience with switchers may be limited compared to others but
>>> most of the problems I have seen have been noise coupled to and
>>> radiated by the incoming power line. The switcher for the amp
>>> filament has an output which is very clean on the scope over
>>> varying loads and input voltages. At the same time, there was very
>>> little detectable RFI from the line cord sniffing across the HF
>>> bands.
>>> 
>>> Well built switchers do exist but it certainly demands a proper 
>>> application of that technology as you pointed out with the coupling
>>> in the ICOM and MFJ examples.
>>> 
>>> Thanks for your comments.
>>> 
>>> 73, Tony W4ZT