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hfx.py is meant to be a full-featured Long Wave / Medium Wave
and Short Wave (250kHz to 30Mhz) AM and Single Sideband receiver.
It uses the USRP with a Basic RX board, and will need an
antenna and some preamps, about 30db gain will work. See the
'Help' menu or hfx_help for more info.
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Powermate knob supported but not required, tooltip frequency display,
single click tuning, AGC, record to disk, play from disk and record
audio. Ability to tailor the audio passband with two sliders over the
spectrum display. The sliders almost align with the actual
frequency. Preset filter settings for LSB (-3000 to 0kHz), USB (0 to
+3000kHz), CW (-400 to -800Hz) and AM (-5kHz from carrier to +5kHz).
AM now switches in a synchronous PLL detector with the carriers at
7.5kHz. The PLL carrier is displayed in the bottom display and helps
show where on the upper spectrum the demodulated signal
lies. Everything gets shifted up 7.5kHz in AM, center frequency,
tooltips, etc. The target AM carrier needs to be closely tuned in, it
will have a hollow sound untill it is locked, and then the PLL carrier
in the bottom display will jump up and remain relatively
constant. There is a slider "AM sync carrier" to play with different
levels to mix with the signal for demodulation. The filter in AM is
preset to 2500/12500 (7.5kHz +/- 5kHz) and is handy for removing
adjacent channel interference. Change AM_SYNC_DISPLAY in script for
whether to show AM Sync carrier or not.
Run with "-h" for command line help with setting USRP ddc center
frequency, decimation, rf data record, playback and audio data
recording.
There are some controls for controlling a varactor and tuning an
antenna - just ignore them unless you want to build a voltage tuned
antenna to track frequency.
There is also code for Web based control of frequency and volume - so
I can tune the radio with an Ipaq from bed. Disabled by default - it
takes a web server, some directories and scripts to use.
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