Spectrum DSP M2 User Manual page 64

Spectrum DSP M2 User Manual V1.1
The use of RX LO HIGH or RX LO LOW is entirely up to the operator's preference, but it may
be observed that additional rejection of some of the noises (e.g. the "tick" from the SPI
communications of the waterfall update to the LCD) may be reduced when one setting is
selected over the other.
For various reasons (e.g. the use of USB on higher bands where the potential for zero-
HZ interference is highest) the use of "RX LO LOW" is recommended for best
performance!
Frequency translation mode is necessary for AM TX and for FM RX/TX operation.
Side-effects of the frequency translation mode:
Spectrum Scope/Waterfall Display offset:
If the menu item "Spec/Waterfall magnify" is set to Off when the translate mode is activated,
you will note that the receive signal is no longer in the center of the spectrum scope or
waterfall display, it is shown at it's offset frequency. Along the bottom of the spectrum scope
you'll observe that the frequency display is changed, with the frequency in kHz being
displayed in full under the graticule, being shifted left or right as noted above. If you have
used other SDR software – particularly "sound card" SDR rigs on computers – you will
already be familiar with this sort of shift!
If "Magnify" mode is activated, the receive frequency is always displayed in the center of the
screen.
Slip-tune mode: [Slip/SP]
quick press & the button shows green when active.
In this mode the stylus is used to drag the receiving frequency and it's carrier bar, across the
spectrum, which if not zoomed, is 192 Khz wide. You can instantly tune across the band
without changing the transceiver frequency, when [Slip/SP] is pressed again, and the CAT
connection is in use, the transceiver will be returned to the current frequency ready for use.
Translation in transmit mode: (for Spectrum's fitted with TX module)
This frequency translation is used on SSB transmit as well, slightly improving the SSB audio
quality when this mode is activated and it also makes it possible to implement the
transmission of AM signals using this type of hardware.
Effects in AM mode:
The use of frequency translation [TUNE/O long-press] removes the DC Zero offset
interference that may occur when using "AM" mode, eliminating the need to off-tune the signal
to prevent its carrier from being at "zero IF". As noted above it has also allowed the
implementation of full-carrier, double-sideband AM: It is also possible to implement single-
sideband, full-carrier AM, but this feature is not implemented at this time.
P 64