User's Manual
Table Of Contents
- Table of Contents
- Introduction
- The Hardware
- Installation
- Getting Started
- Inside the Excelsior
- Resizing the Application Window
- Drop-Down Menu Controls
- Tuning the Excelsior
- Receiver Selection
- Mode Selection
- Function Tabs
- Spectrum Scopes
- Recording Functions
- Attenuator
- Preamplifier
- S-meter
- Top Menu Bar
- File
- Options
- Auto-mute RX not in focus
- Enable second RX
- Filter Length
- Front Panel LED
- Display Offset
- Time
- Keyboard Shortcuts
- VSC Set-up
- Audio Buffering
- AMS Capture Range
- Audio Output
- Show Measurements
- Show Data Rates
- Of particular interest to many users will be the CPU load (excessive CPU load may cause sluggish behaviour or freezing of the computer), and Audio latency. Apart from DDC bandwidth, CPU load may be minimized by reducing the Demodulator filter length (...
- Note: When measuring sensitivity using SINAD, it is very important that the Audio Filter is enabled and the cut-off frequencies (and for FM measurements, also the de-emphasis) are set according to the specified test conditions. Proper audio filtering ...
- Show Waterfall Timestamps
- Calibration
- Hand-Off Receiver
- Color scheme
- Restore factory defaults
- Memory
- Scheduler
- Scanner
- Logger
- Plugins
- Power Switch
- Date and Time Display
- Appendix A – SDR and DDC Primer
- Appendix B – Troubleshooting
- Appendix C – USB Interface Diagnostics
- Appendix D – Dealing with Interference
- Appendix E – G39DDCi PCIe Card Connections
- Appendix F – Waterfall Spectrum Palettes
- Appendix G – Recording File Formats
- Appendix H – Compliance Declarations
- Appendix I – Safety Disposal
WiNRADiO G39DDC User’s Guide
20
Achieving Best Selectivity
In any software-defined receiver, the maximum achievable selectivity is a
function of the processing power of the host computer: The greater the CPU
power, the “longer” (and therefore sharper) can the digital filters be made.
The selectivity of your receiver can be adjusted using the function Filter
length under the top bar menu Options. The greater the Demodulator filter
length parameter, the better the selectivity:
This function also makes it possible to observe the CPU load, which will
depend on this setting. It may not be advisable to select a value resulting in
more than say 30% CPU load as the computer may then become sluggish.
Should the computer become sluggish or even “freeze” as a result of this
adjustment, please reduce the demodulator filter length to a lower value.
Note also that the CPU load can be lowered (while keeping selectivity
high) by reducing the DDC1 and/or DDC2 bandwidths (DDC1 and DDC2
values shown above the two respective spectrum displays). For example,
HF signals can be demodulated with 20 kHz DDC1 and DDC2 bandwidths
without a decrease in the demodulation quality. Wider DDC bandwidths
affect display and recording, while increasing the CPU load
considerably.