Hi
Tony
May be aggressive is a
subjective assessment ,
If CW tx , could be
described as Hard/Aggressive Keyed , that would give
the same results , Ie , Soft keying / envelope shaping
, produces , less side bands or Click's , less envelope
shaping , produces a much harsher / aggressive / wider
signal
A good comparison is
the original MFSK mode and, say, ROS-HF ,
In terms of the on-air
presence , MFSK and ROS are ''identical'' both use
single tone , both change the tone frequency and
duration, as directed by the resolve of the mode coding
and modem design , both are 'base band heterodyned systems
', each may transit via, none linear systems [ OLIVIA has
a phase component to the modem modulation scheme , and as
such , requires linear amplification ]
But, where as the MFSK mode ,
produces a set of near in ‘side band's’ , [ even marked on
the spectrum plot in Patrick’s Multi-psk, as additional B/W
] , ROS-HF can be seen to be clean and producing only
the on air tone set .
The
modem in ROS is Phase continuous , may be other systems are
also, but , the ROS system , embodies design features that
are missing/not as developed from other systems , ''Gray
noise'' is the general term
The audio level
supplied to the Transmitter , remains constant ,
However
, fluctuations may be observed on the TX power meter ,
these , appear to be a by product of the filtering in
the TX . the abrupt changes in Tone , appear to be
subjected to the filter characteristics , phase shift ,
group delay etc, which in turn , adds phase / time
distortion , the resolve of which is amplitude variation
Racal
listed various option fit filters , some , voice , some
data , so i suspect the problem was known about some time
back , two filters in the tx/rx path , 40 MHz roofing and
the 1.4 MHz pass/band , using the widest possible filter ,
can reduce the ‘side bands’, the DSP compensates for
disturbance , but , from a transmission aspect, its better
to maintain the ''waveform''
That probably explains
the different on-air signals , interims of additional
side bands , from a single tone , or at least that’s my
general observation , Tx [ and unseen RX issues] serve to
degrade the signal quality , the claim, no filter is
required , hold quite true , if the DSP is correctly
designed ..
73-Graham
g0nbd