Holy Mackerel!
--- Radio WC6W <wc6w@juno.com> wrote:
>
> Here is my entry into the interesting project
> category -- A Kilowatt
> transistor SSB/FM/AM/CW/etc. transmitter for 160
> through 6 meters.
>
> The transmit chain consists of:
>
> 1. A Mike preamp connected to a 16 Bit Analog to
> Digital converter
> running at a 24 KHz sample rate -- one of the tiny
> ones with serial data
> output.
>
> 2. A 16 Bit Digital Signal Processor chip good for
> about 40 mips. This
> chip can perform an intelligent VOX function (no
> missed syllables) by
> delaying the input signal 10 mS. The same buffer
> can be used to
> implement a Hilbert transform compressor (similar in
> function to RF
> clipping). Transmit bandwidth will be set by
> mode... or whim.
>
> SSB will be generated by the Weaver (third)
> method & the resulting I&Q
> signals will be up sampled by a factor of 32. These
> signals will be
> delayed to compensate for the output filter delay in
> the envelope
> re-modulator filter (part 5 below). A digital
> representation of the SSB
> envelope will be loaded directly into the modulator
> at a 96 KHz rate.
>
> For CW, this critter will also be able to create
> a variety of envelope
> shapes... from textbook perfect to simulated chirps
> & clicks. :-)
>
> FM is created directly by adding the digitized
> value of the mike
> audio, 16 bits - up sampled to 192 KHz, scaled for
> the desired deviation,
> to the nominal carrier setting (32 bits) and
> updating the DDS registers
> with those results (also at a 192 KHz rate). This
> method gives perfect
> FM with ridiculous control over the deviation: 1 LSB
> = .075 Hz @ 5 KHz
> total deviation.
>
> AM is made in the old way, by directly modulating
> the final amp.
>
> And of course PSK, FSK, etc will be doable.
>
> 3. A combination up-sampler, Direct Digital
> Synthesizer & I&Q modulator
> (a single IC) that can directly output on frequency
> up through 6 meters.
> SSB is created by completing the Weaver modulation
> with the second mix
> directly at the output frequency.
>
> 4. A limiting amp (to make Class D) followed by a
> two watt stage which
> may operate either Class A for test or Class D for
> real.
>
> 5. A legal limit Class D amp modulated by a
> switching amplifier powered
> by a power factor corrected (PFC) input circuit.
> Output filtering &
> tuning will be by means a whole bunch of coils &
> capacitors switched
> by... about 32 relays. An independent SWR protection
> circuit will
> directly reduce the voltage to the finals, to
> prevent awful things from
> happening should something screw up in the software.
>
>
> The modulator, sampled at 96KHz, will be driven by
> a digital pulse
> width generator with 11 bit resolution (ECL parts
> -- clocked at 200
> MHz). It will implement the envelope restoration
> for SSB, envelope
> shaping for CW, direct modulation for AM and power
> control for FM, CW,
> AM, & SSB.
>
> The RF amplifier and modulator stages can be line
> isolated by means of
> RF transformers, plus optoisolators for the control
> signals, so no big AC
> power transformer will be required.
>
> 6. and almost forgot -- An 8 bit microprocessor
> to handle the mode
> selection, tuning, etc.driving a Vacuum Fluorescent
> readout for all the
> words & numbers.
>
> Finally, a 24.576 MHz master clock multiplied (by
> 8) to 196,608 MHz to
> clock the DDS & ECL stuff; and divided as necessary
> to run everything
> else.
>
> ******************************************
>
> While this sounds like a lot of stuff, it will be
> rather compact in the
> real world -- except for part 5. :-)
>
>
> Comments, suggestions... anybody want to help?
>
>
> 73,
> Marv WC6W
>
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________________________________________________________________
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>
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