Removed unecessary dependencies on librtlsdr and libusb

• File source plugin does not need libusb nor librtlsdr
• The base software does not need libusb
• FCD libraries should not be included if libusb is not available
• Added a few cosmetic changes to SSB demod and Channel Analyzer

Normalized font face and size so that the text looks similar in all environments

Key features

- Normalized font face and size so that the text looks similar in all environments. Previously some pieces of text were rendered with the default font which resulted in the text looking different depending on the Linux distribution used and./or the global preferences selected. Now the font has been explicitly set to Sans Serif family with a point size of 9 so that text is always rendered in a similar way. - Added instructions in the readme to build in Mint, openSUSE, Fedora and Manjaro

Other changes

- Added in the readme the references to the pre-built packages for openSUSE and Arch (Manjaro) - Added missing tool-tips in the various GUIs - NFM demod pushed volume by 2x - Added some missing dependencies in the readme (puseaudio is mandatory to run the program) - Added paragraph about code organization in the readme - Added frequency units for center frequency in all sample input GUIs

First official release

Changes from SDRangelove

New features, enhancements and fixes

• Added ppm correction for the LO of RTL-SDR. This uses the corresponding function in the librtlsdr interface (range -99..99 ppm)
• Added a preset update button (the diskette with the yellow corner) to be able to save the current settings on an existing preset
• Added variable decimation in log2 increments from 2^0=1 to 2^4=16 allowing to see the full 2048 kHz of spectrum if so you wish
• Better handling of rtlsdr GUI display when settings change (initial load, load of presets)
• Added display and precise control of the shift frequency from center frequency of the NFM receivers.
• Removed useless spectrum visualizer in NFM receivers. Created a null sink class to fit corresponding parameter in NFMDemod class constructor.
• Added display and precise control of the shift frequency from center frequency of the SSB receivers.
• SSB filter bounds are tunable so that filter can be set off from center frequency allowing aural decoding of CW
• Make the sidebands appear correctly on SSB channel overlay. Limit to +/- 6 kHz to fit channel spectrum analyzer window
• SSB bandwidth can now be tuned in steps of 100 Hz
• NFM and SSB receiver in focus trigger the display of the central frequency line on the spectrum frequency scale thus facilitating its identification
• Added AM demod so now you can listen to air traffic!
• Added the possibility to change the brightness and/or color of the grid.
• Make the low cutoff frequency of the SSB filter variable so it can be used for CW also.
• NFM demodulation without using atan and smooth squelch with AGC suppressing most clicks on low level signals and hiss on carrier tails. Only useful modulation comes through.
• Added working WFM demodulation. Optimized for no atan2.
• OsmoSDR and GNURadio plugins removed from the build as they have too many bugs that are too difficult to correct
• New plugin for BladeRF interfacing libbladeRF directly
• Corrected the nasty audio band resampling bug preventing use of sample rates that are not power of 2 multiples of 48kHz. This was because the resampling ratio was calculated with an integer division instead of a float division.
• As a consequence of the above added more interesting values for the available sampling rates of the BladeRF plugin
• Variable span for the SSB demod down to 1.5 kHz
• Filter out CTCSS tones for audio and full CTCSS support in NFMDemod
• Enhancement of the NFM squelch mimicking professional analog squelch circuits (based on balance between two AF filters)
• Added a channel analyzer plugin focusing on measurement (DSA/DSO functionnality). Basic functions.
• Added a scope widget in the channel analyzer plugin
• Channel analyzer bandwidth up to half the available RF (IF) bandwidth (was 48k fixed)
• Enhanced scope display and controls: scale display, better X (time) and Y scales control, grid fit to scale, effectively implementing triggers, trigger on magnitude and phase, properly handling time shift, ...
• Enhanced spectrum display: Histogram: wider decay range, make stroke and late holdoff adjustable. Added option to show live spectrum (had only max hold before).
• Enhanced channel analyzer: enhanced scope and spectrum displays as mentioned above, make the spectrum display synchronous to scope (hence triggerable a la E4406A).
• Sort channel plugins by delta frequency and type before saving to preset
• Implemented scope pre-trigger delay
• Implemented variable scope memory depth
• Implemented trigger delay
• Trigger on both edges
• Spectrum histogram clear
• Trigger line display for all trigger modes
• Coarse and fine trigger level sliders
• Minimalist recording (no file choice)
• File sample source plugin (recording reader)
• Scope: trace history
• Scope: trigger countdown
• Scope: multiple trigger chaining
• Scope: new mode with linear IQ (two traces) on the primary display and polar IQ on the secondary display
• New UDP source plugin to connect to an external demodulator (ex: GNU radio) via UDP ports
• Binaural option for SSB demod
• DSB option for SSB
• Mute option for NFM channel
• New Broadcast FM demodulator with stereo support
• RDS support in Broadcast FM demodulator

Major redesign

• Make the DSP engine global static simplifying access to it. Have a distinct object to handle the thread
• Fixed startup initialization sequence. New initialization phase in DSP engine and new ready state
• Synchronous messaging class to push message to thread and wait for completion relieving the message queuing mechanism from this role
• Message queuing and handling redesign. Still not completely satisfactory
• Objects have their own input and output message queues
• Dedicated message queue to communicate to the GUI for objects coupled with a GUI
• Optimizations with Valgrind cachegrind
• Corrected decimators bit shifting so that the number of effective output bits is constant and fill the internal sample width
• Separate library to support all flavours of FunCube dongles. Rewritten FCD plugins.
• Allow several sample source plugins to share the same presets for what is common
• Prepare grounds for future Tx operations with Tx spectrum display in the main window
• Merged include-gpl into include and removed GPL dribble in About dialog
• Many other little things...

Recent fixes

• Fixed typo in cmake file
• Added .desktop file
• Fixed RTL-SDR sample rate slider range