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<blockquote data-quote="Waveguide" data-source="post: 880926" data-attributes="member: 364636">Got too much coffein today and reading antenna books is a tried andtrusted tranquilizer. The medication was [Per-Simon Kildal - FoundationsOf Antennas p. 331] and [C.A. Balanis - Antenna Theory p. 821].Whatever you do - No overdoses of those please! It's heavy stuff!&nbsp;Both books gives figures for surface accuracy and both end up witha maximal deviation from the optimal shape less than approx. 2 mm tohave small (&lt; 0,3 d<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite6" alt=":cool:" title="Cool&nbsp; &nbsp; :cool:" loading="lazy" data-shortname=":cool:" /> impact on directivity. Their &quot;directivity&quot; isyour &quot;antenna gain&quot;. Rough surfaces makes the central lobe smaller andwider. Small f/d ratio makes it more sensitive to imperfections.(diameter 5000 mm and wavelength 30 mm as input to the calculations)A diagram in [Balanis] gives the same values for directivity as mentionedearlier, 54 to 55 dB. Surface errors will reduce it from this maximal value.&nbsp;Manufacturing method, assembly/installation of antenna parts willdetermine if the dish lives up to whats in the specification.&nbsp;The &quot;finetuning&quot; of the dish in Channel Hopper's image must be somethinginvented after my books were written.&nbsp;... now I feel another double espresso would be nice.&nbsp;(if there are smilies instead of &quot;dB&quot;, blame the forum software)</blockquote>

[QUOTE="Waveguide, post: 880926, member: 364636"] Got too much coffein today and reading antenna books is a tried and trusted tranquilizer. The medication was [Per-Simon Kildal - Foundations Of Antennas p. 331] and [C.A. Balanis - Antenna Theory p. 821]. Whatever you do - No overdoses of those please! It's heavy stuff! Both books gives figures for surface accuracy and both end up with a maximal deviation from the optimal shape less than approx. 2 mm to have small (< 0,3 d:cool: impact on directivity. Their "directivity" is your "antenna gain". Rough surfaces makes the central lobe smaller and wider. Small f/d ratio makes it more sensitive to imperfections. (diameter 5000 mm and wavelength 30 mm as input to the calculations) A diagram in [Balanis] gives the same values for directivity as mentioned earlier, 54 to 55 dB. Surface errors will reduce it from this maximal value. Manufacturing method, assembly/installation of antenna parts will determine if the dish lives up to whats in the specification. The "finetuning" of the dish in Channel Hopper's image must be something invented after my books were written. ... now I feel another double espresso would be nice. (if there are smilies instead of "dB", blame the forum software) [/QUOTE]

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