THROB v2.6 MFSK & FEC, with RIGblaster
(THROB by G3PPT)
Developed for
ionosphere made distortions, weak signal QSOs.
Digital mode approval: http://www.arrl.org/FandES/field/regulations/techchar/
ThrobV2.6 is an EXPERIMENTAL freeware Multi-Tone
Frequency Shift Keyed (MFSK) transmission program evolved while experimenting
with DSP on a PC soundcard. It uses a palette of 9 tones spaced 8 or 16 Hz
apart giving a bandwidth of 72 or 144Hz. There are enough permutations of the 9
tones when used as tone pairs and single tones to allow the encoding of a
modest character set to be sent in a single tone pulse. The tones are sent as a
shaped pulse with the leading and trailing quarters
raised cosine shaped, and the tones are received synchronously, with the synchronisation being set manually or automatically. There
are three transmission speeds of 1 ,2 and 4 Throbs/sec
giving respectable transmission rates of 10, 20 and 40 wpm respectively. The 1
and 2 Throb/sec speed use a tone spacing of 8Hz and a bandwidth of 72 Hz and
the 4 Throb/sec speed uses a tone spacing of 16Hz and a bandwidth of 144Hz.
There is potential to slow it down further for VLF etc. Throb2 evolved from
Throb1, which used three consecutive pulses of 1 tone from a palette of 5. Throb1
had enormous limitations but showed that tone techniques can have advantages at
low level, that amateur radio gear is able to function
with techniques requiring a stability of 3 or 4 Hz, and that radio amateurs can
readily use it. The use of raised cosine shaped tones gives a characteristic
"throbbing" sound, hence the name of the method.
Hardware:
A RIGblaster (1ea), Soundcard speaker
cables: Radio Shack-42 2387 (3ea).
RIGblaster:
Strap P1 to match your radio's
Microphone. (i.e. RJ45 IC706 page 9). Set Audio Level
Control full clockwise.
Swith VOX/AUTO to AUTO, apply
power. Cable RIGblaster to
radio and
computer, as shown in RIGblaster manual’s hookup diagram; (PC Speaker Out to
Rigblaster In; PC Aux. In to
Rigblaster Out). The RIGblaster interface will allow computer speakers
to continue to operate for music etc.
Note: Don't use low impedance un-amplified
speakers.
Computer Downloads:
Install to THROB26 folder:
Throb26.zip and unzip
Create a THROB26 shortcut Icon
Reboot computer
Windows Sound card setup:
Master Volume: Master Volume to 1/3 of
the way up - Balance slider to the center
Wave Volume to 1/3 of the way up - Balance slider to the
center
Line In
Volume to 2/3 of the way up - Balance slider to the center
Microphone Volume to 1/3
of the way up
PC Speaker Volume to 2/3
of the way up
Recording Controls: Line In SELECT -
Volume to 1/3 of the way up - Balance slider to the center
Note: Turn the computer speaker volume control
knob most of the way, but not all of the way down.
Radio setup:
Set all IF Filters to OFF (or as wide as
possible)
Set Audio RF to MAX
Set VFO to: 14080.0
Set Transmitter output power to ¼
manufacturer’s rated RF power output, 25 watts or
less is a good
operating setup for a 100 watt transmitter and to provide linear performance.
Set Mode to USB (convention)
Set Processor to OFF and SWR ON
Adjust Tuner for 1:1 with the normal
output on CW
Set ALC to ON and SWR OFF
Speak into the microphone, adjusting MIC
control so that ALC doesn’t occur above the
ALC Zone indicator. (use a Dummy
Load)
Connect antenna (Dummy Load will give bad
ALC reading in Digital setup)
Adjust Tuner for 1:1
Click on Tx button (transmission starts).
Adjust RIGblaster
Audio Level Control, stopping as transmitter output power reaches MAX
(ie. 25 watts) keep an eye on your ALC so
that ALC does not occur; run with NO ALC
indicating
occurring; any ALC indicating, results in your TX Signal being distorted,
and causing
harmonics.
Click on RX button to stop TX
Note: The RIGblaster Audio Level Control is
the most precise way to adjust the
Soundcard output voltage into the
radio. The Microsoft Volume controls were
designed to
vary the voltage, through a range of reasonable outputs for Speakers;
They were not designed to be adjusted
so precisely as to be reliable set to
5 millivolts.
ALC can remain (on) to control drive
limit.
Recommended frequencies:
1838.0 3580.0
3584.0 7035.0 7072.0
7073.0
10147.0
14080.0
18105.0 21080.0 24929.0
28080.0
Operation:
Set up:
Click on THROBv2.6 Icon
Click Set Up – Enter CALL - Select COM1 – Click
OK
Select Speed 4 LSB (2 Throb/sec (default))
Select: AFC ON – Select AutoSync On
There is a small screen provided (Other
Station) for entry of the call-sign of the station with which you are in
contact. Once the call-sign has been entered then the CQ and QRZ macros will
operate and when clicked, will place CQ and QRZ texts into the transmit window
ready for transmission.
Three further macros allow
for small text files (less than 255 bytes) that have been edited into the same
directory as Throb26.exe to be read and placed into the transmit window ready
for transmission. These should be named "1.TXT", "2.TXT"
and "3.TXT" respectively. Click on THRON26 Folder – with Notepad write
three files:
File name 1.TXT (File text ie: BTU kn kn kn)
File name 2.TXT
File name 3.TXT
On running the program, there will be a pause
and then the waterfall display should appear and show a moving representation
of the audio spectrum. Adjust the sensitivity of the waterfall display to suit
conditions using the Track-Bar provided. If the lines across the display are
shown as red then the input is overloaded and the soundcard audio-control
window should be called up and the line-input level adjusted accordingly. By
the same means the audio output level may be set to suit the transmitter, and
it may be considered an option to leave this window displayed.
There are two screens for reception. Because
the Throb mode is sideband sensitive, both LSB and USB versions are printed and
the user can disregard
A "tune up" single tone is provided
when in transmit, and this runs continuously until it is cancelled. Note
however, that when tone pairs occur in actual transmission, these add and
subtract to give peaks and troughs and hence great potential for OVERLOADING.
Please keep an eye on your ALC so that this does not occur; it is safest to run
with NO ALC indication occurring. Nothing gives a linear mode such as this a
bad name so quickly.
A button has been provided to stop printing
when not required, as the method will print on noise.
Spend time with the test facility which gives
practice on locating the central tone for accurate tuning. Note how the receive
window between the red bars widens for the 4 Throb/sec speed. Observe the
operation of the AFC after deliberately clicking the tuning 1 or 2 Hz off
frequency.
sub-spectrum between
800 to 1111 Hz is displayed on a waterfall display. Mouse clicking on the
sub-waterfall display window enables the band-pass to be moved within the
sub-spectrum for tuning within about 1Hz. The blocks of filtered data are then
normalized up to the level of the peak data in the block and then shifted into
the right hand side of a memory area holding the previous data block. A display
of this data allows the troughs between the raised cosine pulses to be seen and
clicking on the display allows the sample start position for a second FFT to be
synchronized with the incoming data or it the program can do this
automatically. A vertical red line denotes the sample start position. The
second FFT calculates the position and intensity of the tone frequencies and
these are displayed as green vertical lines in the third graphic display. The
character is decoded from this information and displayed in one of two memo
displays. Because the data is sideband sensitive, (another major disadvantage
of Throb1), the inverted data is also decoded and displayed in the second memo
display, thus making the technique insensitive to the sideband used with the
opposite sideband data being obviously garbage which can be ignored.
Tuning is tricky, but a test routine is
provided to allow practice. Note that the idle character uses a single tone
positioned at dead center The first three pulses of
the test routine and also of transmitted data will be this single central tone,
so tuning by mouse clicking on it should set up the reception for the following
data. The tuning/stability requirements are great with initial tuning within
plus or minus 3 Hz and then maintenance of this position. The initial tuning is
fairly easy with the resolution of the waterfall display but maintenance of the
position has required the deployment of AFC (button provided) which will shift
the window in 1Hz increments to maintain the tones in the central FFT bin for
that tone.
Note that the program starts with the AFC and
the Autosync. Facilities enabled, and you should see
the AFC bring the tuning window into line and the red sample start position bar
should position into a trough automatically. In practice, these facilities
should be left ON.
To Transmit:
Click on THROBv2.6 Icon
Type other Station’s CALL in Other Station
window.
Type text message in the TX window
Click on Tx ON
(text is transmitted)
Click on Tx OFF
to stop transmission.
Spectrogram setup:
Click on GRAM4264 Icon (spectrogram
window is activated)
Click FILE
Click F4 Scan Input (set Scan Input
parameters)
Click OK (view signals on frequency) set
VFO that receive signal to start at 400Hz
To Exit: Click STOP - FILE - EXIT
Characteristics:
The program uses a Pentium
based PC equipped with Windows95 and a soundcard. The soundcard runs at 8000Hz
and uses data blocks of 2048,
4096 or 8192 16 bit
samples. for the three speeds of 4, 2 and 1 baud respectively.
Pairs or single tones out of a palette of 9 in a 72 or 144Hz bandwidth are sent
and received sequentially, each tone being 2048, 4096 or 8192 samples long and shaped as a semi raised cosine "throb" in that
the leading and trailing quarters of the block are raised cosine shaped. The
permutations of single and pairs of tones out of a palette of 9 allow for a rudimentary character
set to be sent in a single pulse. For reception, the 72 or 144Hz bandpass (obtained via FFT and reverse FFT filtering) is
positioned centrally over the signal, and then the presence and position of the
tones is our unit of coding.
Synchronization of the reception process to the incoming
"throbs" is used, and can now be set automatically.
References:
http://www.qsl.net/dl5swb/
Test equipment software:
Audio Signal Analyser:
SpectrumLab v204b29 (speclab24b29.zip) www.xs4all.nl/~nl9222/software.htm
Oscilloscope, Dual-trace: WinScope 2.51 ( osc251.zip) www.electronicsaustralia.com.au/cgi-bin/downloads.pl?area=5
Spectrogram v5.0.8 (gram517.zip) http://neasmn.org/ben/software/software.htm
Spectrogram v4.2.6 (gram426.zip)
Analyzer 2000 v5.04 (Pay for) www.dxzone.com
MUF Charts: http://www.arrl.org/qst/propcharts/
DX Spots: http://hamcall.net/dxspots
DX Summit: http://oh2aq.kolumbus.com/dxs/
DX-Telnet v5.2 http://www.golist.net
Reflector: http://groups.yahoo.com/group/hellschreiber/
(search THROB)
VE9DX – RN6A – OH2LU – S51MA
Joe Mettle sends: