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Re: LF: WSPR sidebands

To: [email protected]
Subject: Re: LF: WSPR sidebands
From: DK7FC <[email protected]>
Date: Sun, 27 Mar 2016 23:14:43 +0200
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...AM key-clicks. Hasn't that been a quality title in the good old QRSS times, called dog-boning?
I've always been happy when i saw some of them in W1VD's captures :-)

73, Stefan

Am 27.03.2016 23:01, schrieb Graham:
Opera's AM key-clicks ,
VERY  True , there  has to be an associated  bandwidth, however ,  hard  non-conditioned on off  keying  of  a  carrier  will  produce , key-click's  , this was the  subject of a  e-mail , sent to  me some time  back, over my  TX bandwidth  on  477 /op8 .
Notably , the  email  enquired as  to  how  my Tx b/w  was  in the  order of  10 MHz or  less and not  the  mode usual  400 / 500 MHz
Its quite  simple,  I use  the  audio  drive  , via a  totally  linear  TX path  ma1723 > skanti amp
What appears to be a  simple  task,   is often quite  complex , as is the  use of the  R-PI as a  rf carrier  source
The  integrity of the  timing loops [ as before] are  compromised  by the  higher order  IRQ requests ,  hence  setting  a  flag high/low , with  a  executed code routine  to  generate a 'stable'  carrier  source  cannot be relied on.
In the  development of the  Opera  R-PI tx code ,  the  action  of the  IRQ's could be  observed as random  noise , acting   cycle  by  cycle , hence any  long persistence  in the  spectrum plot , simply  masked the  spurs , however , the  Opera  dsp  returned varying  s/n  levels  for the  same  test  set up , indicating the  channel  background noise varied. [ opera decoder  is a  sampling system running far faster than the  data  rate ]
The  project was  shelved , other than for  hard on-off  keying  of a  free  running  carrier ,  in this the  clock  jitter is  of no consequence.  

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