Re: Packet rates HF/VHF/UHF under part-97

Rick Muething


It is important to separate and understand terms:

Modulation type: Common types are: Frequency shift keying FSK, sometimes called nFSK, 4FSK, 8FSK etc) Phase shift keying (PSK, BPSK, 4PSK, 8PSK etc.)   Quadrature amplitude modulation( QAM combination of Phase and amplitude  e.g  32QAM etc )  and a few other less common ones (Chirp etc) . 

A protocol (e.g. Pactor, WINMOR, Robust Packet, ARDOP etc) uses one or more of the above modulation schemes with a complex and detailed set of protocol rules to allow data transmission (FEC or ARQ) and synchronization. Each protocol will have a detailed public document that tells how it works.

The 300 baud limitation (US)  currently applies to all amateur frequencies under 29.0 MHz  It says basically that the max symbol rate (1 symbol per second is 1 baud) on ANY carrier is 300 symbols per second (or 300 baud). [note a symbol may contain 1 or more bits...e.g. one symbol of 8PSK modulation represents 3 bits) ]. Many protocols (Pactor, WINMOR, ARDOP etc) use 2 or more simultaneous carriers and this is usually referred to as OFDM (Orthogonal Frequency Division Multiplex,  which allows multiple simultaneous and closely spaced carriers to not interfere with each other).  In practice symbol rates above 300 aren't too practical on HF because of multipath distortion. Pactor 4 with its mechanism for channel compensation is an exception and has some modes over 300 baud.

There is no "Winlink protocol"  (Winlink is a communication network and currently supports the following HF protocols: Pactor 1-4, WINMOR, ARDOP (using BPQ), Robust Packet (300 baud HF packet).  There has been some experimentation with VARA (a new low baud high number of carriers 2.4 KHz mode).

Different rules apply above 29 MHz and VHF/UHF.


Rick Muething KN6KB  Winlink Development Team, Developer of WINMOR and ARDOP.

On 10/7/2017 12:28 PM, Graham wrote:
Q what  are the  maximum  packet rates  ?

HF  300 baud packet  , limited by the  max  300  baud  rule  ?  
if  using  other  modulation system,  then over  300 baud is  possible ,  eg winlink  etc ?

Is there  max  baud  rate  for  vhf   , norm   is  1200  for   2  meters  and  9600  for  70  cm  
of just  max  b/w  of  signal ?


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