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<blockquote data-quote="RimaNTSS" data-source="post: 906811" data-attributes="member: 312276"><p>TBH, I am little bit lost here. Still do not see usefulness of f/d ratio of the offset dish. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite10" alt=":oops:" title="Oops! :oops:" loading="lazy" data-shortname=":oops:" /> OK, "d" is probably stands for diameter (horizontal axe). But what is "f"? Distance fro antenna's focal point to where? <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite12" alt="o_O" title="Er... what? o_O" loading="lazy" data-shortname="o_O" /></p><p>Not all producers of converters show f/d. I think that it is much easier to show opening angle of antenna in degrees and as well illumination angle of LNB also in degrees. </p><p>For example, from another thread we know that IBU's illumination angle is 84*. And I know for sure that 2 old Prodelins (0179-189) have opening angle of 78*. So, IBU is little bit overiluminating my dish. </p><p>How to make antenna's opening angle and LNB's illumination angle match each other? I think there couple of ways to do this matching: find LNB (or feedhorn) with proper illumination angle, and another way - to make "matching device", we spoke about such a device in another thread and thread still not finished. </p><p></p><p>I need some time to do precise measurements of my last Prodelin, according to what you've said before it should have opening angle about 70*.</p><p>I am also bit confused about types of Prodelin feedhorns when one of then is 39* and another one 50*. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite9" alt=":eek:" title="Eek! :eek:" loading="lazy" data-shortname=":eek:" /> What those angles mean in practical sense?</p></blockquote><p></p>
[QUOTE="RimaNTSS, post: 906811, member: 312276"] TBH, I am little bit lost here. Still do not see usefulness of f/d ratio of the offset dish. :oops: OK, "d" is probably stands for diameter (horizontal axe). But what is "f"? Distance fro antenna's focal point to where? o_O Not all producers of converters show f/d. I think that it is much easier to show opening angle of antenna in degrees and as well illumination angle of LNB also in degrees. For example, from another thread we know that IBU's illumination angle is 84*. And I know for sure that 2 old Prodelins (0179-189) have opening angle of 78*. So, IBU is little bit overiluminating my dish. How to make antenna's opening angle and LNB's illumination angle match each other? I think there couple of ways to do this matching: find LNB (or feedhorn) with proper illumination angle, and another way - to make "matching device", we spoke about such a device in another thread and thread still not finished. I need some time to do precise measurements of my last Prodelin, according to what you've said before it should have opening angle about 70*. I am also bit confused about types of Prodelin feedhorns when one of then is 39* and another one 50*. :eek: What those angles mean in practical sense? [/QUOTE]
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