Ken -
What you are actually seeing on the Panadapter are the low audio
frequencies in a 'HiFi SSB' signal ie., freq. from about 50Hz to 250Hz. In
an adult human voice, the greatest power in the spectrum is in that region
and it falls off 6 to 10dB /octave. If for example, at 100Hz the power is
-50dBm, at 200Hz it could fall to -58dB, at 400Hz down to -66dB, at 800Hz
down to -74dB and so forth. What is displayed is NOT carrier, but low
frequency audio energy! This is why it is important for folks experimenting
with high quality SSB audio to understand how to control the dynamic range
and frequency passband of the transmitter. IMHO, some operators have far
too much low frequencies in their signal, but, that is another topic!
If we allowed a tiny amount of the suppressed carrier to leak thru, then
we could 'auto-tune' such an SSB signal by using the SAM mode ie.,
synchronous AM. In the early days of SSB, experiments were done using a
'pilot carrier' about 20dB down from full output ( 1% ) and this allowed
PERFECT TUNING of an SSB signal automatically! There are other ways to
autotune SSB too and DSP might make the job easier.
Hope this makes sense!
73, Alan Davis -K2WS-
From: Ken N9VV <[EMAIL PROTECTED]>
To: FlexRadio Reflector <FlexRadio@flex-radio.biz>
Subject: [Flexradio] SSB carrier visible on some signals?
Sent: Sunday, June 5, 2005 7:49 AM
Dear smart Panadapter guys,
I frequently see SSB signals on 75m and 20m that have a vertical line right
under the zero line on the Panadapter. The line amplitude seems to vary with
the speech and the bandwidth of the guy who is talking.
Some signals (many) seem to have what looks and sounds like a carrier
bouncing up/dwn at about 30db below their speech peaks. Is that their
carrier?
why do their rigs generate a carrier when on SSB? most of the modern rigs
advertise 50db or more of carrier suppression.
Is the Panadapter so good that we can actually see the carrier? if so - that
is w-a-y cool!
de Ken
