O P E R A T I O N C H A P T E R 6
Set the TX Meter (4) to ALC and adjust for 0dB to calibrate transmit. Click on Receive on your
digital mode program and PowerSDR should switch back to receive.
6. You are now ready to begin a QSO. If a 50 ohm dummy load was connected, connect an
antenna in its place. Tune to the desired frequency using one of the methods outlined in the
Tuning Methods section above. Select either DIGL or DIGU (6) for lower or upper side band
digital mode operation respectively. Select DRM (6) for DRM mode operation.
Note 1: The DIGL, DIGU and DRM (6) mode buttons bypass all signal
processing in PowerSDR, except for AGC and Filtering. With DIGL and
DIGU you have control over the filter width using the filter buttons
(7). DRM mode invokes a fixed 10kHz wide double side band filter.
Note 2: DIGL and DIGU (6) apply an offset when using Spectrum Click
Tuning (see page 67). By default, the offsets are set to 1200 Hz
(SSTV) in DIGU mode and 2210 Hz (RTTY) in DIGL mode
respectively. These offsets can be modified on the Setup Form -
General Tab, Options Sub-Tab.
Separately, so called RTTY Offsets (for DIGU and DIGL mode) can
be applied to the VFO A (and/or VFO B) frequency, before CAT
reports it to a third party program (see page 105). These offsets can
be modified on the Setup Form – CAT Control Tab.
Hint 1: When operating digital modes you have two options with regard to
using filters. On the one hand you can use a wide band-pass filter in
PowerSDR and use the filters within your digital mode program for
selectivity.
On the other hand you can home in on a specific signal with
PowerSDR’s filters and ignore the filters in your digital mode program.
Although circumstances and operator preference will dictate which to
use, many operators have found the second option to be especially
valuable to them. However for very narrow and/or steep filters, the
latency versus minimum filter bandwidth trade-off holds just as much
as with CW. See Appendix A for more detail.
Hint 2: Please check our Knowledge Center (http://kc.flex-
radio.com/search.aspx) for more articles on how to use PowerSDR
with various digital mode programs.
If you already have VCOM and VAC up and running, you may ignore the following sub-sections.
We will now focus on installing and setting up N8VB’s VCOM driver and VAC. We will then use MixW as
an example on how to use these utilities to operate digital modes.
148 2003-2009 FlexRadio Systems
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