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Message-ID: <65AECDF1F89AD411900400508BFC869F0D7490@pdw-mail-1.dera.gov.uk>
From: "Talbot Andrew" <ACTALBOT@dera.gov.uk>
To: rsgb_lf_group@blacksheep.org
Subject: RE: LF: PSK sidebands
Date: Fri, 15 Dec 2000 11:36:01 -0000
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We're thinking along the same lines.  I tried a PWM modulator a few
months ago - it is shown in the latest LF experimenters book - but this
required an 8 bit digital input for the PWM.  It could modulate rails up
to 50V at 10A but could be expanded.   Tried the concept with a (badly
generated) PSK31 waveform on 1.8MHz with sucess, but the poor generation
due to the way I encoded the waveform using 6 bit amplitude sampled at
500Hz,  generated unacceptable sideband levels at the 500Hz sampling
rate.  Never carried on any further as this project was not a priority
then.

The only switching PAs I have at the moment are the experimental big
ones, so these look a contender for the next PWM supply controller.
There's a challenge, a 0-100% duty cycle 340V controller using PWM !

Andy  G4JNT


> 
> If one is serious enough about civilized PSK sidebands to 
> consider linear 
> amplification-- which is no trivial matter at the "California 
> kilowatt" > Class C, D, and E amplifiers are not that hard to
modulate.  
>> stages, apply PWM 
> methods to the power supply for the final!
> > If the amplitude component and RF phase/frequency components 
> are reunited in 
> the final amplifier without excessive time difference, the > 


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