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Feedhorn Channel Master, Laminas, Invacom QDF
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<blockquote data-quote="archive10" data-source="post: 1010082"><p>That is quite baffling... you must have quite a special dish.</p><p></p><p>As discussed in earlier post, if the GI 209 does not give better results, then the chances of finding a "magic feed-horn" than delivers dramatic increases in reception are quite slim.</p><p>Only feedhorn alternative I know of could (and only just could) be the SMW XM-601, which has the f/D specced between 0.45 and 0.65 (with 0.55 being ideal, as their OA-800, 1050 and 1400 reflectors were).</p><p>You may find these from time to time on e-bay (but I can't find any at the moment).</p><p></p><p>The only other options I see are to review your dish thoroughly - maybe someone fitted non-original feedarms at some point, and the feed is nowhere near in the focus point?</p><p>With your measurements, you can calculate the exact distance that the feed needs to be from the centre of the dish.</p><p>Several members, perhaps most notably [USER=312276]@RimaNTSS[/USER], can elaborate on how you do that.</p><p>Then you can check if the feed is dead-center, and at the right distance.</p><p></p><p>If all this fails, there is still the possible, but perhaps devastating possibility that your 2.4 meter dish was</p><p>a) either badly made, ie. the shape is nowhere near the perfect parabola, or</p><p>b) the dish was originally made for C-band, which means that Ku-band performance may be bad no matter what you point at.</p><p></p><p>The parabola shape you can check by carefully (!) measuring point along a diameter, and try and approximate a paraboloid to those measurements.</p><p>Then measure all around the dish to make sure it is radially consistent (as seen when rotating the dish along the mid-axis).</p><p>This will take time, and is best peformed indoors with dish lying on it's back.</p><p></p><p>The C-band possiblity can be checked by pointing dish as 19.2E, and compare the strength (on your Rover) with reception info from a "normal" sized steel dish as the same location pointing at 19.2E.</p><p>You should be getting at least 10 dB more signal from 19.2E, depending on the size of the small dish.</p><p>If you get much less, he dish may not be up for the task...</p></blockquote><p></p>
[QUOTE="archive10, post: 1010082"] That is quite baffling... you must have quite a special dish. As discussed in earlier post, if the GI 209 does not give better results, then the chances of finding a "magic feed-horn" than delivers dramatic increases in reception are quite slim. Only feedhorn alternative I know of could (and only just could) be the SMW XM-601, which has the f/D specced between 0.45 and 0.65 (with 0.55 being ideal, as their OA-800, 1050 and 1400 reflectors were). You may find these from time to time on e-bay (but I can't find any at the moment). The only other options I see are to review your dish thoroughly - maybe someone fitted non-original feedarms at some point, and the feed is nowhere near in the focus point? With your measurements, you can calculate the exact distance that the feed needs to be from the centre of the dish. Several members, perhaps most notably [USER=312276]@RimaNTSS[/USER], can elaborate on how you do that. Then you can check if the feed is dead-center, and at the right distance. If all this fails, there is still the possible, but perhaps devastating possibility that your 2.4 meter dish was a) either badly made, ie. the shape is nowhere near the perfect parabola, or b) the dish was originally made for C-band, which means that Ku-band performance may be bad no matter what you point at. The parabola shape you can check by carefully (!) measuring point along a diameter, and try and approximate a paraboloid to those measurements. Then measure all around the dish to make sure it is radially consistent (as seen when rotating the dish along the mid-axis). This will take time, and is best peformed indoors with dish lying on it's back. The C-band possiblity can be checked by pointing dish as 19.2E, and compare the strength (on your Rover) with reception info from a "normal" sized steel dish as the same location pointing at 19.2E. You should be getting at least 10 dB more signal from 19.2E, depending on the size of the small dish. If you get much less, he dish may not be up for the task... [/QUOTE]
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Feedhorn Channel Master, Laminas, Invacom QDF
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