[hpsdr] thor

[Phil Harman]

Hi Alex,

That is exactly what is planned. Basically you build a switching PSU
running at say 200kHz.  You use the your modulation envelope signal to PWM
the PSU and that gives you a DC voltage that varies in sympathy with the
modulation.

At bit like the AM modulators we built years ago. There is one significant
difference.If you think of the envelope of an SSB two tone test signal
then as the envelope passes through zero volts the signal rapidly changes
direction. You need a wide enough  LPF to pass this signal but still able
to attenuate the (200kHz say) switching frequency.

This is one of these techniques that 'works beautifully on the white
board' :-).

Not sure about Murray's comment on rectifying the mains directly. Our
washing machine does this and does not have a mains transformer to be seen
- and produces the most QRN of any device I've ever come across!

73's Phil...VK6APH



> ***** High Performance Software Defined Radio Discussion List *****
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> alex wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> why bother having a separate modulated psu, why not run the pa off
>> rectified mains and modulate the duty cycle.
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> Hi Alex,
>
> I don't know about the US, but in Australia I think it is illegal to
> rectify the mains directly. There must be a transformer first.
>
> Murray VK6HL
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