JTDX  is a  computer  program  designed  to  facilitate basic  amateur
radio communication using very weak signals.
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JTDX  Version  2.2 offers six different  protocols or modes: FT4, FT8,
JT9, JT65, T10 and WSPR.
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FT8 is the most popular mode of communication, JTDX  provides  matched 
filter and own statistics based FT8 decoders with possibilty to decode 
some signals as low as -30 dB SNR in  a  2500 Hz  bandwidth.  JTDX FT8
decoders do use  information  collected  from  previous  intervals  to
decode signals in last interval.
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FT4 mode was initially designed for contesting, now being also used to 
make fast contacts usually within continent.
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T10 is forked JT9 mode especially designed  to  withstand   HF Doppler 
frequency spread caused by radio wave dissipation by ionosphere or  by 
reflection from fast moving polar  lights. T10  mode  uses  dual  tone 
synchronization pattern allowing to decoder distinguish harmonics from 
base signal. Also T10 provides excellent band capacity  with  improved 
decoding of overlapped signals versus JT9 mode.
Both JT9 and T10 decoders can decode signals as low as -28 dB  SNR  in 
a 2500 Hz  bandwidth.
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WSPR (pronounced  `whisper`) stands for (W)eak  (S)ignal (P)ropagation
(R)eporter.   The WSPR  protocol  was designed  for probing  potential
propagation  paths  using   low-power  transmissions.   WSPR  messages
normally carry the transmitting  station’s callsign, grid locator, and
transmitter power in  dBm, and they can be  decoded at signal-to-noise
ratios as  low as  -28 dB  in a  2500 Hz  bandwidth.  WSPR  users with
internet  access  can  automatically  upload reception  reports  to  a
central  database called  wsprnet  that provides  a mapping  facility,
archival storage,  and many other  features. WSPR has a  new companion
FST4W which has  a similar message content but offers  up to 30 minute
transmission periods for greater sensitivity on LF and MF.
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JTDX  provides spectral displays for  receiver passbands as wide as 5
kHz,  flexible  rig control  for  nearly  all  modern radios  used  by
amateurs. The program runs equally well  on  Windows,  Macintosh,  and  
Linux systems, and  installation packages  are available for all three
platforms.
