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Receiving |
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- Start here....
Open WSJT and from the menu bar select Mode and JT6M or press Shift+Control+F7. You should now see purple box with JT6M as in
Picture 2 (Ver 4.x.x) or Picture 3 (Ver.5.x.x) below.
Now click the Monitor button and you are now in receive mode.
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The default setting for S is -10. S sets minimum increase in signal that will be accepted as a ping. Set to -10 will give less "rubbish" decodes than -12 setting but you may not be able to decode weaker pings. Try different values and see the effect when receiving
some JT6M signals. |
Tol sets the decoder tolerance (in Hz) to frequency offsets. Default setting is 400 (Hz).
This means that signals up to 400Hz from rx frequency can be decoded. This is the DF value in the WSJT decode pane - the DF value shown in
Picture 1 below is -32 - this has produced a very good decode.
When the DF value has been established you can reduce it to near zero
by either using the RIT control on your transceiver or retuning the VFO. If you already txing, i.e. started a qso, you should reallly use just the RIT control as your
qso partner may have already heard you and made similar adjustments; retuning the VFO may cause confusion. Of course if the DF value is greater
than 400 then it is probably better to retune the VFO. When the DF value is low ,<20hz say, decrease the value of Tol to reduce
the probability of false decoding - a figure of 50 is usual. However be aware that your qso partner's tx may drift and cause the DF value to
increase (or decrease). |
At this point Auto is OFF button is set so you won't inadvertently transmit any JT6M signal.
If you are in Europe, tune you receiver to 50.230MHz (adopted random calling qrg) and listen for pings/bursts. |
- Receive Level
When receiving, the object is to maintain a "green line" level equal to 0dB ±1dB on rx with NO signal (JT6M)
received. This is indicated on the status bar at the bottom of the WSJT window - RX noise : 0dB. See pictures 1 and 2. In picture 1, the
"green line" and a small MS burst as received from LA1TV can be seen. If you look at either end of the "green line" you will see a little black line
just outside the waterfall display. This corresponds to 0dB setting and is a useful guide.
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Depending on how noisy your 6M environment is, you may have to adjust your rig's AF level and/or the sound cards
input level (via Windows Mixer) frequently to maintain as near to 0dB RX noise and a comfortable listening level. |
If you can, set your rig's AGC to OFF. Also, switch off your rig's in-built speech compressor if
fitted when txing. |
- Decoding
If you hear some pings/bursts, remember that if it is not automatically decoded, you can click on the "green line"
in the waterfall pane (Picture 1). You will be surprised what can be decoded, even if you didn't hear anything ! WSJT Ver.4.7.0 comes with
Spectran. This is very useful tool and it is possible to see weak pings/bursts even if not heard.
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Clicking with the left mouse button decodes a 4-second block of data near the mouse pointer.
The right button uses a longer segment of 10 seconds. Drag the mouse with the button down to select any desired region. Experiment for best
decoding as necessary. |
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Picture 1. |
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- The decoded line in Picture 1 shows - 093300 11.8 1.9 6 -32 CHE LA1TV G0CHE LA1TV G2CH
File ID : 093300 - time of start of receive period and part of "saved" wav file name
T : 11.8 - time of start of decoded burst
Width : 1.9 - length of burst (in secs)
dB : 6 - max. signal level (in dB) above "green line"
DF : -32 - frequency difference (in Hz) from TX frequency (in this case LA1TV is 32Hz lower)
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Picture 2 - WSJT Ver 4.x.x |
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Picture 3 - WSJT Ver 5.x.x |
- Frequency and Ping Strength
Unless your qso partner is way off qrg, stay put and use RIT control to "fine tune" with relation to the DF reading
of decoded message. e.g. if DF is -73 then set RIT to -73 or near as possible. It should then give DF of near 0 for future QSO decodes. Once done you can change the TOL setting to say
100 or 50. This will improve you decodes. You may also want to set the "Min Ping Strength" - "S" to -12 or more although this will also give more garbish decodes.
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- File Saving
WSJT program has the option to save either all received periods, save last or save decoded.
Check the programs menu's. Be warned that the RXWav folder soon fills up as each saved .wav file is about 310kB !!
Here is a sample file you can save this to disk and play back in WSJT using File/Open from the menu bar.
From an imcomplete qso with K7BV on May 9 2004 around 1500z k7bvg0che.wav about 319kb
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- DECODED.CUM
Another option available via File menu option is "Save Text in File DECODED.CUM" allowing
all decoded text to be saved for future reference. Note that this file will grow with use/decoded text. An option to delete is also available
via the File menu. The DECODED.CUM file can easily be read with Notepad or similar text program.
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- A Glossary of WSJT Terms can be found here.
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