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References: <4DAF42C1.8010401@telus.net>
Date: Wed, 20 Apr 2011 21:50:59 +0100
Message-ID: <BANLkTik1nVPsUHhN=OM=2Vco5X=_7=SQoA@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@gmail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: MSK with a Class D transmitter...?
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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
www.g4jnt.com

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 <sthed475@telus.net> 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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<div>I assume you are genrating the MSK=A0from soundcard output, in which=
 case two options come to mind:</div>
<div>=A0</div>
<div>1)=A0 Double the frequency.=A0 Full wave rectify the audio sinusoid,=
 pass the AC part of the result into a comparator and into=A0the divider.=
=A0 Alternatively,=A0as the signal bandwidth is probably quite low, square=
 up the audio to start with, feed into one inpiut of an XOR gate.=A0 Delay=
 the waveform by 90 deg and feed this into the othe side of the XOR.=A0=A0=
=A0 Output of XOR to divider as before</div>

<div>=A0</div>
<div>2)=A0=A0 Remove the=A0 divide by two, and replace with an inverter /=
 buffer pair to generate the out of phase drive signals.=A0=A0 The=A0=A0in=
put now needs to be close to a 1:1 squarwave at output frequency.=A0=A0 Pa=
ss the soundcard audio into a comparator and make sure it gives a 50% duty=
 cycles.</div>

<div>=A0</div>
<div>=A0</div>
<div>Andy</div>
<div><a href=3D"http://www.g4jnt.com/">www.g4jnt.com</a></div>
<div>=A0</div>
<div>ps.=20
<div>or 3)=A0=A0=A0 Convince the software author the S/W needs modifying=
 to give a 2.F output</div></div>
<div>=A0</div>
<div>=A0</div>
<div class=3D"gmail_quote">On 20 April 2011 21:32, Scott Tilley <span dir=
=3D"ltr">&lt;<a href=3D"mailto:sthed475@telus.net">sthed475@telus.net</a>&=
gt;</span> wrote:<br>
<blockquote style=3D"BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8e=
x; PADDING-LEFT: 1ex" class=3D"gmail_quote">Hi All<br><br>I wonder if some=
one can explain to me how to feed an MSK signal into a typical Class D tra=
nsmitter?<br>
<br>I mean by typical that the TX has a 4013 type /2 system feeding two FE=
T drivers to drive FETs in a push-pull configuration.<br><br>If I understa=
nd correctly due to the fact MSK does not have amplitude component to its=
 signal that a non-linear transmitter can be used.<br>
<br>So, how do you do this with a Class-D TX as often used in LF/VLF?<br><=
br>Thanks,<br>Scott<br>VE7TIL<br><br><br><br></blockquote></div><br>

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