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The diagram below shows the equipment used on board, this enabled us to send digital pictures from "The Alderman" to other amateurs each day. Daily contact were made on the 14MHz band, with Idris GW3TLP on the Isle of Anglesey. Other regular contacts with, Alfred DK1OT in Stuttgart, Charlie 9H4CM in Gozo, and Gerry VK6GW in Perth. Examples of
received pictures are attached.
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The Laptop Computer : The computer used was a Toshiba, however any laptop will provide the necessary audio signals, providing it has a sound card, and is able to run Windows 98 / XP. Processor speed needs to be in excess of 900MHz for reasonable decoding of the digital picture.
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Brian GW4KAZ at the operating desk. |
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Interface Unit : This simply is a box which incorporated a switch which provided a PTT signal for the transmitter, plus a change-over switch for microphone input or computer. It also provided a test point between the computer and the transceiver . Transceiver : Aboard "The Alerman" was a Kenwood TKM707 transceiver, this is a marine band HF transceiver. The original frequency coverage was HF marine bans only, however having studied the circuit diagram, modifications were made to allow the transceiver to operate on the amateur bands. The TKM707 is capable of 150w PEP. This proved very useful on the amateur bands. Automatic Antenna Tuning Unit: Since the antenna used on board was effectively an end fed slopping vertical (the mast's back stay) the automatic ATU was an essential part of the equipment, in providing a perfect match between the transceiver and the antenna.
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Software: The software used was developed by
Erik VK4AES and allows pictures to be encoded and decoded for transmission. Pictures were taken using a digital camera, and downloaded into the computer. Text was simply added to the pictures before transmission by use of the paint software in Windows.
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The Alderman's back
stay as antenna |
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