kopia lustrzana https://github.com/jamescoxon/dl-fldigi
54 wiersze
1.8 KiB
Plaintext
54 wiersze
1.8 KiB
Plaintext
/**
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\page feld_hell_configuration_page Feld Hell Configuration
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\tableofcontents
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<br>
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\image html config-feldhell.png "Feld Hell Config Panel"
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\image latex config-feldhell.png "Feld Hell Config Panel" width=5.0in
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The Hellschreiber modes all use a video display that is basically a
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character-by-character facsimile. The shape of the characters is
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determined at the transmitting station. You can select from 15
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different fonts, all of which have been designed for Feld Hell use.
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In normal use each dot of the character font is transmitted
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twice. You can increase the effective video s/n by transmitting
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the dots 2 or 3 times the normal. That is controlled by the
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Transmit width. <br>
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<br>
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FeldHell is a pulse amplitude modulated
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signal. The shape of the pulse is a raised cosine. This
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helps to control the bandwidth of the transmitted signal. It is
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customary to use a 4 millisecond risetime for the raised cosine,
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especially on HF. You can change that to 2 milliseconds.
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The video edges will be sharper, but the bandwidth twice as
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large. You might find 2 msec a better choice for VHF and above.<br>
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<br>
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Fldigi provides three controls for the receive function. The video is
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normally black on white. You can change that to white on black.
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You can also compress the horizontal scan rate of the video.
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You might find this effective in displaying received fonts that
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are broad (or if the other end is using a multiple dot transmit width).<br>
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<br>
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As
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you change Hellschreiber modes the optimum filter bandwidth will be
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set. You can change that and might find a narrower filter
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effective if you are experiencing CWI interference. FeldHell is
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susceptible to CWI. If you narrow the filter the received video
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will become blurred.<br>
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<br>
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\ref feld_hell_configuration_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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<br>
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<br>
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