Ten-Tec OMNI-VII User Manual page 31

The two most-used SSB transmit controls
will be mic gain (accessible from the
MIC/MON button on the front panel) and the
speech processor (accessible from the
SP/VOX button on the front panel).
Mic gain is set by pressing the MIC button
and talking into the microphone. When you
have reached proper ALC, the red ALC LED
located next to the S-meter on the front of
the radio will flash on voice peaks. Adjust
the mic gain upward until the ALC light is
flashing on and off while you are
transmitting. Different microphones will
require more or less gain.
To account for differences in microphones
used with OMNI-VII, a hardware mic gain
control is also provided. This control is
accessible via an access hole at the front
bottom of the transceiver, near the mic jack
at the junction of the molded front panel and
metal bottom cover. This hardware mic gain
control is before the microphone input
amplifier. A simplistic description of the
signal path input would be: microphone >
hardware mic gain potentiometer >
microphone amp > A/D converter > DSP.
The software mic gain control adjusted with
the MULTI knob is at the DSP level.
The hardware mic gain control is set to
maximum as supplied from the factory to
accommodate proper level for Ten-Tec
microphones. Should your non-Ten-Tec
microphone of choice be subject to easy
overdriving, the hardware mic gain can be
reduced. Please note that the hardware mic
gain pot at full CLOCKWISE is at minimum,
and full COUNTER-CLOCKWISE is
maximum. This is as seen with the
transceiver upside down and a tool inserted,
not as if the transceiver is right side up and
facing you.
Speech processing (SP) is provided to give
the operator more "punch" to the transmitted
signal. Speech processing increases the
average amplitude relative to the peaks for
an increase in average power transmitted.
Press the SP button (if desired) and use the
MULTI knob to adjust the speech processing
level. Speech processing is generally not
used for higher-fidelity SSB audio; its use is
primarily for added intelligibility for
communications-grade SSB audio. It is also
possible with high levels of speech
processing and combinations of microphone
588 manual
Part #74409
Printed in USA
and other settings available to send the
transmitter into distorted SSB output. Use
the monitor function to listen to what you are
transmitting and avoid this.
The speech processor used in the OMNI-VII
is a DSP generated RF compressor.
Human voices have peak-to-average ratios
as high as 15 dB. At 100 watts PEP output,
the average output power might be as little
as 3 watts! RF compression raises the
average output power and tends to improve
intelligibility by bringing out subtle parts of
speech. With a digitally generated RF
speech processor, we have the advantage
of calculating the RF envelope before
modulation is performed.
Note on wide SSB transmit bandwidths:
Audio fidelity generally improves with the
use of wider SSB transmit filtering. Using a
3.0 kHz or higher bandwidth will have a
more "well-rounded" audio response than a
narrower bandwidth. As transmit bandwidth
widens, so does the potential for
interference with stations using adjacent
frequencies.
Part 97 of the FCC regulations governing
amateur radio operation does not specify a
maximum transmit bandwidth usable by
amateurs for SSB communication.
However, FCC regulation 97.307(a) requires
amateur stations not to occupy more
bandwidth than is necessary for the
emission type being transmitted in
accordance with good amateur practice.
Regulation 97.307(b) requires that
emissions outside the necessary bandwidth
must not cause splatter interference to
operations on adjacent frequencies.
While these are broad regulations subject to
interpretation, the responsibility for
complying with the regulations rests with the
operator. Using an SSB transmit bandwidth
wider than necessary for communications
and causing interference to adjacent
stations while doing so is specifically what
these regulations are addressing. In
summary, what may be an acceptable
bandwidth on a given band at a given time
may not be on another band at another time.
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