kopia lustrzana https://github.com/jamescoxon/dl-fldigi
63 wiersze
2.3 KiB
Plaintext
63 wiersze
2.3 KiB
Plaintext
/**
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\page feld_hell_page Hellschreiber
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\tableofcontents
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\section hell_modem Hellschreiber modem
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All Hellschreiber modes are based on character scanning, reproducing
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characters in a similar way to a dot-matrix printer. This technique uses a
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digital transmission, yet allows the received result to be interpreted by
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eye, a similar concept to the reception of Morse by ear. The character is
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scanned upwards, then left to right. There are typically 14 pixels
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(transmitted dot elements) per column (although single pixels are never
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transmitted) and up to seven columns per character including
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inter-character space.
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<br>
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These remarkably simple modes are easy to use, easy to tune, and
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although not especially sensitive, are entirely
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suited to HF/VHF since they use no sync and the eye can discern the
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text even in high levels of noise. fldigi can operate in the
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following :
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\section hell_modes Hellschreiber modes
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<center>
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Mode | Symbol Rate | Typing Speed | Duty Cycle | Bandwidth
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:------------|:------------|:---------------------|:------|:--------
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Feld-Hell | 122.5 baud | ~ 2.5 cps (25 wpm) | ~ 22% | 350 Hz
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Slow Hell | 14 baud | ~ 0.28 cps (2.8 wpm) | ~ 22% | 40 Hz
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Feld-Hell X5 | 612.5 baud | ~ 12.5 cps (125 wpm) | ~ 22% | 1750 Hz
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Feld-Hell X9 | 1102.5 baud | ~ 22.5 cps (225 wpm) | ~ 22% | 3150 Hz
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FSK-Hell | 245 baud | ~ 2.5 cps (25 wpm) | ~ 80% | 490 Hz
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FSK-Hell 105 | 105 baud | ~ 2.5 cps (25 wpm) | ~ 80% | 210 Hz
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Hell 80 | 245 baud | ~ 5.0 cps (50 wpm) | 100% | 800 Hz
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</center>
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\section hell_waterfall Hellschreiber Waterfall
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Feld-Hell look like this when being received by fldigi:
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<br>
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\image html feld-hell.png "Feld-Hell, Slow Hell, Feld-Hell X5, and Feld-Hell X9 are all pulse"
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\image latex feld-hell.png "Feld-Hell, Slow Hell, Feld-Hell X5, and Feld-Hell X9 are all pulse" width=2.69in
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<p>Feld-Hell seems to be the most commonly used and use can usually be found
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on 80 and 40 meters at the high end of the digital sub bands. Extreme
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linearity is required in the transmit path in order to control the bandwidth
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of the transmitted signal. Feld-Hell X5, Feld-Hell X9 and Hell 80 should
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probably not be used on HF in the US. They can be used on VHF
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and UHF.</p>
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<br>
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\ref feld_hell_page "Return to Top of Page"
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<br>
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\ref main_page "Return to Main Page"
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*/
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