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Feb 16th, 2006 at 8:33am
Cables:
For a 2 watt BUC, RG6 is good for up to 30m. Above that use RG8 up to 100m or RG11 up to 80m. In the case of long cables, heavy duty types with low DC resistance and low RF attenuation are needed. Note that the transmit power setting will have to be adjusted to correspond to the cable length and uplink power needed into the satellite.
If the cable is very short, start with the transmit power very low, otherwise you may overdrive the BUC and maybe damage it, also any overdrive will distort the transmitted signal and reduce the BER at the hub and interfere with other peoples transmission bursts on adjacent return link frequencies. The LinkStar output level is adjustable -30 to -5 dBm and the BUC input may be specified as say -20 dBm MAXIMUM input for output at the -1 dB compression point. The LinkStar output level setting is in 0.5 dB steps so that -t -40 means -20 dBm
A most important aspect of the cables is perfect and well weatherproofed connections at the ends.
Regarding feed rotation:
Wrap a strip of paper round the feed tube and make pencil end marks where it meets. Unroll and then measure the circumference length L mm, which is equivalent to 360 degrees.
Measure length S from one end where S = L * 81.5/360 mm and mark this final setting angle.
Start with the feed set to nominal Horizontal or Vertical polarization as specified, and then rewrap the paper round the feed tube with ends marks at the top. Then turn the feed 81.5 deg anticlockwise (while facing the satellite) so the setting mark S is now at the top.
Best regards, Eric.
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