HF Explorer Help

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 Command Line Switches:

	-c	DDC center frequency, set band.
		-c 7.2e6 or -c 7.2M for 40 meter ham band.
		Default is 3.9e6 80 meter ham band.
		Example:

		hfx.py -c 9500k 

		starts up in the 31 meter band.

	-a	Audio output file. Output file for 32kHz two channel
		signed word audio. Two channels are used for
		independent sideband. This file can be converted
		to a wav file with sox. Example:

		sox -c 2 -r 3200 file.sw file.wav

		sox needs the .sw extension to indicate file type.
		If not specified no audio file is created.

	-r	Radio output file. File to write RF data to for later
		demodulation. Records the entire band to disk, width
		determined by sample rate/decimation. Be sure to
		note the decimation and center freq for later use!
		Example:

		hfx.py -c 900e3 -d 80 -r rf_data_AM-c900e3-d80

		writes a pre-demod rf file centered on 900kHz with a
		bandwidth of 800kHz (That's 80 AM stations!). The
		center and decimation could be put in the filename for
		proper use later.
		If not specified no rf data file is created.
		At default 250 decimation disk usage is about
		8Gb / hour.

	-i	Radio input file. Use to play back a previously
		recorded rf data file. Example:

		hfx.py -c 900e3 -d 80 -i rf_data_AM-c900e3-d80

		plays back the previously recorded band, no
		usrp hardware needed. Tune about the 800kHz wide band.
		When playing a recorded file, time controls
		fast-forward and rewind are available.
		
	-d	Decimation. Sets sample rate and bandwidth.
		This is the factor that the usrp sample rate, 64e6,
		is divided by. Default is 250 for 256kHz bandwidth
		which is enough to record a ham band without 
		eating up disk space too fast. The 64e6 sample
		rate limits the upper practical frequency to 32MHz.
		The Basic RX transformer limits the lower frequency
		to about 200kHz. 


 Powermate Knob:

	A Powermate knob is recommended but not necessary. If a knob
	is used, it is in one of 3 or 4 modes controlling frequency,
	volume, filter and (if playing a recorded file) time.
	Pushing the knob switches mode and the buttons on the HFX panel
	change to show which mode is in effect. Then just turn the knob
	to set frequency, volume, filter or go fast forward or rewind.


 Bandswitch:

        Across the top are a set of predefined bands and buttons
        to rapidly switch to the center of that band. To change a band,
        type the frequency in Hz into the box under "Center Frequency",
        then press "Set" on the left, then the button you want to
        program. From then on (untill the program is exited) pushing
        that button takes you to that band.  To make a band button
        permenant edit the hfx.py script with whatever frequency you
        want assigned to what button.


 Frequency:

	There are 6 ways to set the frequency.
	1) Move the slider with the mouse
	2) Use the Spin Control up/down arrows (very fine 1Hz control)
	3) Type the frequency in Hz into the Spin Control
	4) Turn the Powermate knob
	5) Web control.
	6) Clicking on the FFT display to set demod center. This is very
	   convenient for tuning +-15kHz when you see a signal on the
	   display. If in Lower Sideband, clicking just to the right of
	   a signal will tune to it immediately. Clicking several times
	   on the far right right or left of the display will rapidly
	   tune up or down the band.


 Volume:

	Move the volume slider with the mouse, or push the Powermate knob
	untill the volume button is active, or click on the volume button,
	then turn the knob. Volume can also be set by web control if web
	control is setup and enabled.


 Filter:

	Similar to volume, switches in any of 30 audio filters from 600
	to 3600Hz in Sideband or up to 5kHz in AM.


 Mode:

	Demodulation modes are chosen by clicking on the buttons for
	Lower Sideband, Upper Sideband, or AM.


 PGA:

	PGA slider sets the rf gain in the Analog-to-Digital converter
	before digitizing. 0 to 20db gain easily shows up on the FFT
	display.


 Time:

	When playing back a recorded RF data file, you can enjoy the
	freedom of rewinding or fast-forwarding. Replay a weak signal
	or skip through annoying AM commercials.


 Antennas and Preamps:

	The USRP Basic RX board is not sensitive enough for anything but
	the strongest signals. In my experience about 40 db of small
	signal gain is required to make the HFX as sensitive as other
	receivers. Some working amplifiers are the Ramsey PR-2 with 20db
	gain, fairly low noise and more bandwidth than we can use here.
	Also the amp modules from Advanced Receiver Research are nice.
	I use an ARR 7-7.4MHz GaAsFET 29db amp with .5db noise at the
	apex of a 40 meter dipole with excellent results. Another
	amp I like is a Minicircuits ZHL-32A 29db amp but they are
	expensive and hard to find. Also it may help to use some filters
	to keep strong local signals from the ADC, or limit rf input
	to the band of interest, etc.  
	Resonant outdoor antennas, like a dipole, in a low-noise (away
	from consumer electronics) environment are nice.  Long random wires
	with a tuner work. I like a small indoor tuned loop made from 10ft
	of 1/4" copper tube, a 365pf tuning cap and a pickup loop connected
	to rg-58. 


 Web Control:

	To control your radio remotely, ensure you have a web server
	(Apache, etc) working and a compatible directory structure in
	place. Directories /var/www/cgi-bin/commands and
	/var/www/cgi-bin/state must already exist. You will need a
	home page with forms and a set of scripts to put commands in
	and put the current state on the home page. email me for further
	help. Setting WEB_CONTROL to True in hfx.py turns on the timers
	that check for commands and update the state.


 IF Output:

	There is a provision for outputting un-demodulated complex 
	through the audio out in stereo for use with Digital Radio
	Mondial (DRM) or using a seperate demodulation program like
	SDRadio (by I2PHD).
	Set IF_OUTPUT to True in weaver_isb_am1_usrp4.py.


 --Good luck and happy LW/MW/SW Exploring.
	Chuck
        chuckek@musicriver.homeunix.com