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
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