This version of the  ROS MF data  mode  is coded to  allow  the  direct use of a  sound card  for  -on frequency-  transmission and  reception  on the  8Khz band ,

 

As the  mode is  coded  with a TX and RX  centre frequency  of  8962.5  Hz , the  PC becomes  a software  defined  stand alone ?radio?

 

To  accommodate  the  use  of  class  e/d  amplifiers  with  ?divide by 2? function  in the  drive chain, the tx toned  may be  switched to   16 Khz with   X2 deviation , which after  amplification, reverts to  the  8 K  parameters

 

Notably this  is a  live data  mode  (as all  ros modes)  so  there  is no  requirement for  accurate  PC  time setting  and  offers  a  wide ?AFC?  range of  78 Hz negating  the  need  for  high  initial  frequency  stability or ?net?  the  system  is tolerant  of upto  5 Hz drift  after  initial  lock

 

Notes for its installation / use are posted along with the zip exe file,

 

Note -  you  will  need  to  have the  normal HF/MF  version  installed  and working  , before the  vlf  exe  will  run   

 

Obviously  Ros-vlf  cannot bend the  laws  of physics and is a  live  keyboard  data  mode  with  0.4  baud  rate , so  signal  levels will  need  to  be  higher than  those required for  slow time base  ?trace?  observations  , however from initial  tests , it is  functioning well  below  audible  levels ..  Its  advisable to  observe the  mode working at HF at the  higher  baud rates to  gain a overview of its  operation.

 

https://sites.google.com/site/uk500khz/ros-vlf---exe

 

 

Data  summery

 

Frequency  tx/rx           8950-8975  Hz           

Bandwidth                    25 Hz

Baud rate                     fixed  0.4   /  (0.8 not posted)

Rx AFC range              78 Hz

Drift tolerance               5 Hz

S/N  0.4  Baud             -38 dB