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My suggestion:
Use two outputs from the stereo soundcard:
An "amplitude" and a "phase" channel. The output from the phase
channel will be a square wave, coherent, constant amplitude, fed
to the divider chain. The "amplitude" channel delivers, well, the
amplitude (as a waveform with variable voltage) which, after
rectification, drives the final voltage via an additional mosfet.
I think the software option is already there, and iirc it has been
used (by Jim ?) for an LF PA.
This way, you could even use amplitude shaping if the bandwidth
(from the hard-keyed PA) was a problem - which I don't think it
is, on VLF.
Cheers,
Wolf
(p.s. problem with the "very long command lines" already fixed,
new SL version will be uploaded soon).
Am 29.12.2013 02:43, schrieb Stefan Schäfer:
Am 28.12.2013 23:33, schrieb Markus Vester:
[...]
PS Any progress on bypassing
the
divider in your VLF transmit chain?
Aaah, no, i forgot that. So i cannot transmit OP32 on VLF
because it
would be incoherent then. So i have to key the PA via a VOX
and OP32
tones, still :-/
In this H bridge PA config, an exact 50% duty cycle isn't
needed, so i
may actually remove the divider. But then i need a solid and
defined
input signal wave form! How do i get an inverted signal then?
A
transformer isn't possible since i like to have a wide
frequency range
of the PA. So far it works from 10 Hz to > 100 kHz. With
the
frequency divider, the wave form can be quite distorted, no
problem
unless the peak reaches the necessary voltage level. So maybe
it is
better to build the VOX circuit instead? Also i want to leave
the PA
circuit as it is, for nostalgic reasons :-)
Or do you have another idea? I remember that circuit with the
XOR
gates...
73, Stefan/DK7FC
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