Message-ID: <ECD2E2BAE2074AA7AEFC5C06168AC5BF@AGB>
From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <4DAF42C1.8010401@telus.net>
In-Reply-To: <4DAF42C1.8010401@telus.net>
Date: Wed, 20 Apr 2011 22:15:48 +0100
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Subject: Re: LF: MSK with a Class D transmitter...?
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Scot

Big  problem  is if  you  have a  division  in the  drive  train ... depends 
what  mode  you  want to  transmit , if  you  can  select a  shift  x2  or 
x4  the  required  , then  you  can  drive  down the  divider train , which 
in turn  reduces the  deviation to the  required level  by /2  or  /4

harmonics  are  another  way , bit  messy  , but say to  tx  wspr  on 500 , 
take the  first  harmonic  of the 'correct'  500 wspr  drive , 1 MHz @ shift 
x2 , > filter>    then  present this to  the  divide /2  driver  chain , tx 
is then  500  'correct'

Gary  has used this to  TX ROS  and WSPR on 500  in the  past  via his class 
D amp

There  was / is a  version  on ROS MF that  could  be  used to  drive a DDS 
, (although  time  expired  , will  run if the  pc  clock is  retarded)

The  ROS  8 KHz  data  mode  has a  class E/D  setting, where  the  TX audio 
drive  is  outputted at  16KHz  , with  x2  shift , to  simplify the  use 
of a  logic  drive  amplifier ..

Patrick  of  MULTIPSK , did  code a  special test   version  that  produced 
a  x2  shift  , that  may  be  of  use ,

It all  depends  which  mode  you  want to  transmit .......

However  , something  that  may  of  passed  un-noticed  , Jim's   design 
for a  EER  transmitter   uses a  pair  of  complimentary output  devices  , 
thereby allowing   the  direct  amplification  of  any  mode  , without a 
divisional  drive  system to  produce the  'complimentary'  drive  to the 
final ...

G..





--------------------------------------------------
From: "Scott Tilley" <sthed475@telus.net>
Sent: Wednesday, April 20, 2011 9:32 PM
To: <rsgb_lf_group@blacksheep.org>
Subject: LF: MSK with a Class D transmitter...?

>
> 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
>
>
>
>