Selective decoding/ Facility update
- Selective decoding/ Facility update
From 3 August 2011, A new ROS Mode will become active , this mode, now has
provision for selective decoding and it will not be compatible with the
present ROS Mode.
A new switch is added, All / `call-signe'
In position ALL , ROS will decode any message (recommended for SWL operation),
In position `call-signe' it will only decode transmissions from the
station with the entered `call-signe'.
Thus , with two stations in qso, the channel may be used by other
NB This facility is only available to the ROS-HF modes , MF and EME
being FSK based and of very narrow bandwidth, are not afforded this
The single hop digital repeating facility
The single hop digital repeating facility is also now made avaialble,
repeating is under the control of the station opertor, who may select
the mode from the menu, then , station with the pre-fix R- to the
call Signe will be re radiated , with crc check on the data content .
This facility may provide , via the cat link, cross band operation , it
is not intended to replace a full packet network , but provides a
useful extension to operations in difficult locations and cross linking
, noting this may also be accessed via the established internet remote
Of particular interest to those operating under the SS directive.
On a more finer technical point , one that has to date been some what
over overlooked , I must admit , I had not noticed this until , looking
back over some off air captures of 500 khz beacon tests, however I have
confirmation this is accurate.
Where as the ros system is distributed as a single .exe file, the
composition of the ROS EME and MF modes is in actuality fundamentally
The MF modes , being unable to take advantage of the BW=Noise gain , the
coding is restricted to FSK , and is therefore eligible for operation
within the existing fcc/ss dictates
Operators are invited to observe a eme or mf mode beacon, using ,
eg, speclab and it will be noted the transmitted pattern is repeated ,
demonstrating in the most simple way , that , no randomizer is deployed and
at 50 and 100 Hz B/W respectfully , clearly the concept of spectral
dispersion is not applicable.
This information , I feel will be of interest to those who are genuinely
involved in the development of data modes as it demonstrates dispersion
techniques are in fact self limiting , noting that the existing
directives of 300 baud and ss are not seen to sit comfortably , untill
other such changes are implemented , this may present a area of development
For example the mf-7 mode affords a s/n gain round 10db over the well
established psk31 , coupled with a total loss of 'gray' noise , due to the
phase cont modulation schema.