[hpsdr] PWM / PDM

[Mack Rogers]

Frank, you goofed on Steve Cloutier's callsign, it's
WA1QIX, website is
http://www.classeradio.com/wa1qix.htm .

Mack Rogers
N4VGB


--- FRANCIS CARCIA <carcia at sbcglobal.net> wrote:

> ***** High Performance Software Defined Radio
> Discussion List *****
> 
> > Hi Guys,
>   I've been playing with PDM am since the early '80s
> and would be glad to answer questions provide
> information links to anyone who requests them. There
> is a basic problem with pdm and any switcher at low
> duty cycles. The filter after the switch isn't
> perfect so at some point a pulse goes in but no DC
> comes out. This is usually around 10 % modulation
> and lower when there is a step of distortion. My
> current mode modulator in my 160 meter AM rig does a
> bit better close to 6 % but I still see the step.
> I'm working on a modulator to support my big 75
> meter class e final motivated by a pair of 2.5 KVA
> isolation transformers. The high voltage switching
> part is actually fairly easy with isolated drivers
> or opto isolation and floating circuits. Check out
> WA1QEX's web site on class e transmitters and
> modulators.
>   Steve has collected a pile of stuff over the past
> 10 years and sells boards for different projects.
>   I am presently looking at an interleaved buck
> design using a TI chip. I'll be glad to share the
> design after it is working. 
>   I've built the CCI- MRF 429 300 watt final for a
> friend and it worked well. Efficiency went down a
> bit on 160. I think the transformers were running
> out of steam. Quality stuff otherwise. 
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