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Its the shift that's the
problem , going for a x2 audio may
drop you out side the ssb filter pass
band .....
Sent: Wednesday, April 20, 2011 10:09 PM
Subject: Re: LF: MSK with a Class D
transmitter...?
Bin too quick to type..
NOt thinking straight...
You need to the upconvert either the resulting doubled audio tone by twice
the RF carrier, or upconvert first and double the final RF. Same ideas for
frequency doubling can be used.
Must fully check before hitting SEND !
Andy
G4JNT
On 20 April 2011 21:50, Andy Talbot <[email protected]>
wrote:
I assume you are genrating the MSK from soundcard output, in which
case two options come to mind:
1) Double the frequency. Full wave rectify the audio
sinusoid, pass the AC part of the result into a comparator and into the
divider. Alternatively, as the signal bandwidth is probably quite
low, square up the audio to start with, feed into one inpiut of an XOR
gate. Delay the waveform by 90 deg and feed this into the othe side of
the XOR. Output of XOR to divider as before
2) Remove the divide by two, and replace with an
inverter / buffer pair to generate the out of phase drive signals.
The input now needs to be close to a 1:1 squarwave at output
frequency. Pass the soundcard audio into a comparator and make
sure it gives a 50% duty cycles.
Andy
ps.
or 3) Convince the software author the S/W needs
modifying to give a 2.F output
On 20 April 2011 21:32, Scott Tilley <[email protected]> wrote:
Hi All
I wonder if someone can explain to me how to
feed an MSK signal into a typical Class D transmitter?
I mean by
typical that the TX has a 4013 type /2 system feeding two FET drivers to
drive FETs in a push-pull configuration.
If I understand correctly
due to the fact MSK does not have amplitude component to its signal that a
non-linear transmitter can be used.
So, how do you do this with a
Class-D TX as often used in
LF/VLF?
Thanks,
Scott
VE7TIL
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