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
49
Audio Filter
The Filter button turns on the Audio filter. The audio filter is a bandpass filter
with continuously adjustable lower and upper cut-off frequencies:
When the audio filter is enabled, its low and high cut-off frequencies can be
adjusted using the Low and High controls. The De-em control is used to
adjust de-emphasis, relating to the filter’s slope from the highest frequency to
the lowest, which is particularly important for FM signals (a typical de-
emphasis value for narrow-band FM-modulated signals is 6.0 dB/oct).
However, it can be also useful for AM signals: Gently sloping the filter
passband can sometimes make the signal easier on ears and avoid operator
fatigue.
For wide FM modulation (broadcast FM), there are two standard de-emphasis
values to choose from, 50 and 75 microseconds:
In North America, 75 microseconds is the standard value, while most of the
rest of the world uses 50 microseconds.
The audio filter passband is shown as a shaded area inside the Audio
spectrum, which is accessible by pressing the Audio button: