The new VARA FM 3.0 modem #VARA


Graham
 
Edited

The new VARA FM 3.0 modem
Some notable  new features in the  latest version of the  VARA-FM  

The modem is  configured  as  two  bandwidths , as well  as automating , level
and link  set up
 , whilst providing  gateways with the  option to  allow , connecting  stations to 
automatically  determine the  mode , wide or narrow  

Narrow , as replacement for the  traditional  1200  Baud voice  channel

9 Speed levels:   1098-12091 bps

Wide  , to replace   9600  Baud , 

11 Speed Levels: 1098-25210 bps

Thye new modem offers  improved  sensitivity , resulting in higher  transfer rates , compared to
the  previous  versions , compatible with  established Vara-linked  e-mail  systems  and the  Chat module ,  

Note- The  tag 'FM'  is used to  imply that  , no frequency  error  can be  tolerated 
ie , FM channel  , where the  modulation  'audio' spectrum is  not  dependant 
on the  tx/rx off  set as in SSB ,

The new  modem is  capable of  providing  cross  connections , as  in , stations set up  for a  particular  b/w  , may now  interconnect, with  its opposite . Narrow > Wide , 

A gateway , for  example , may  [now]  be  configured   'wide'   
and still  allow  connections  , from a   station ,  configured  
'narrow'  A compatibility  chart  is  provided  :-

Mode compatibility

Client

Gateway

Connection

NARROW

NARROW

NARROW

WIDE

NARROW

NARROW

NARROW

WIDE

NARROW

WIDE

WIDE

WIDE


Auto TX Delay.

The new VARA FM measures and shows the TX Delay of your station  and Optimises  the link,  , where  as previous versions , required  user input , this is now automated 

NB:This TX delay mechanism support's  PTT via VOX,  such  as provided by the Signalink USB interface.

TXmeter.png



Auto Drive Level adjustment. VARA FM has a new AutoTune button, which optimises the  drive level , ensuring link establishes 'at maximum  speed / best s/n

Autotune.png


Overall  view of the  modem  structure / speed levels  

 

VARA FM WIDE

VARA FM NARROW

Level

Symbol Rate

Carriers

Mod.

Net Rate (bps)

Symbol Rate

Carriers

Mod.

Net Rate (bps)

1

42

55

4PSK

1098

42

55

4PSK

1098

2

42

55

4PSK

2253

42

55

4PSK

2253

3

42

98

4PSK

4040

42

55

4PSK

3022

4

42

98

4PSK

5387

42

55

8QAM

4032

5

42

98

8QAM

7185

42

55

16QAM

5375

6

42

98

16QAM

9580

42

55

32QAM

6720

7

42

116

16QAM

11340

42

55

64QAM

9072

8

42

116

32QAM

14144

42

55

128QAM

10585

9

42

116

64QAM

19003

42

55

256QAM

12091

10

42

116

128QAM

22102

 

11

42

116

256QAM

25210

 






73-Graham 
g0nbd