ROS QRG 70.074.0 USB NOTES ON USING ROS

[G0NBD]

NOTES ON USING ROS

Some may know , some may not , listed are some points that may be useful , as the operation is not quite as expected , when used to digipan etc



The ROS digital mode package contains three separate data transmission systems, all the modes are ‘live’ keyboard modes , the baud rate / bandwidth determining the performance ,ie, maximum from wide/slow minimum narrow / fast . There is NO requirement for time locking of the pc , tx/rx must be the same mode , usb is the norm

All the modes are single tone MFSK and may be transmitted via non linear systems

EME , centre frequency 1500 Hz 50 hz b/w– fixed b/w & speed

HF centre frequency 1500 Hz 2.0 K and 1 Khz 500 Hz mode , 4,8,16 baud

MF centre frequency 1500 Hz fixed 98 Hz B/W , 7 & 1 Baud

Why define a frequency, ? , Operating frequency 70.074.0 USB dial

To receive a ros transmission , the initial synchronisation frame of the transmission ‘must’ be received , with out this the software will not lock . It is ‘not’ possible to causally intercept a ros transmission , the receiving station must be available and within the AFC range at the start of the transmission for the syc process to start , unlike conventional rtty or psk etc.

As it is possible for reception to take place at a signal level below the audible threshold or visibility on spec-lab , interception is only practically possible in such cases by prior tx/rx frequency alignment.

All of the data systems are suitable for use , the eme mode has a wide afc range , where as the HF and MF modes afc lock are much less , the MF mode is so called as it was coded to fit the 100hz data bandwidth of the EU 500K permits, MF-7 offers significant advantage over psk31. A 1 Khz audio test tone is available with in the set up menu

The AFC function serves only to allow the RX to lock to the transmission and displays the offset in Hz , it will ‘not’ follow a drifting signal . The TX frequency is fixed and there is no provision for NET as in the more usual spectrum/waterfall tuned packages .


For monitoring purposes, it is possible to run more than one session of ROS , set to different modes / bandwidth , i.e. ROS HF 2.2 K all speeds and ROS HF 500 all speeds , while maintaining the same usb dial set.

http://rosmodem.wordpress.com/


G ..

[G0NBD]

First qso G0NBD/G4WGT

Main problems with the frequency stability of my transverter ...ok after warm up but still drift , also 145 meg drive freq is perhaps not the best as well

could be some issues with aircraft flutter

Netting was major problem , the 1 K tone helped to keep netted onto Gary ..

Frequency netting is important