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<blockquote data-quote="Vipersan" data-source="post: 648651" data-attributes="member: 325666">Hi CH ..In actual fact ..my Alcoa 1.8pf was never equipped to receive C band&nbsp; ..in fact when I bought it 20 odd years ago ..it was fitted with a tube feed with an in line mechanical polarizer and an OMT with 2 single polarity lnbs for High and Low band.The feedhorn was nothing more than an open ended&nbsp; KU waveguide ...with no scalar rings or actual horn of any kind.The boss was never wide enough to accomodate a C band LNB ...so I had to redesign the mount boss in aluminium ...and everything thereafter to allow the cheapo pauxis polarity H/V switched lnbf to be retrofitted .It could be argued that since I appear to require the dielectric material to extend out beyond the lnbf throat ..that it isn't correctly positioned at the dishes focal point ...but believe me I've tried every conceivable postion ...and the one which best suits ..ties with the calculated fd of the dish...Without the extended dielectric T ...there is absolutely no possiblity of getting AFN on 1 west ..But with it inserted I get a stable ..watchable picture.I guess I just got lucky ..both with the construction ....and with the chosen material for the dielectric plate.What is interesting is that an identical cut slab (T shaped) of identical thickness ptfe/Teflon gives about 10% less signal ..sorry for the life history ....but I guess I can't push any more out of my setup..just wishful thinking.<img src="https://www.satellites.co.uk/styles/default/xenforo/smilies/smile.png"&nbsp; class="smilie" loading="lazy" alt=":)" title="Smile&nbsp; &nbsp; :)" data-shortname=":)" />rgdsVS</blockquote>

[QUOTE="Vipersan, post: 648651, member: 325666"] Hi CH .. In actual fact ..my Alcoa 1.8pf was never equipped to receive C band .. in fact when I bought it 20 odd years ago ..it was fitted with a tube feed with an in line mechanical polarizer and an OMT with 2 single polarity lnbs for High and Low band. The feedhorn was nothing more than an open ended KU waveguide ...with no scalar rings or actual horn of any kind. The boss was never wide enough to accomodate a C band LNB ...so I had to redesign the mount boss in aluminium ...and everything thereafter to allow the cheapo pauxis polarity H/V switched lnbf to be retrofitted . It could be argued that since I appear to require the dielectric material to extend out beyond the lnbf throat ..that it isn't correctly positioned at the dishes focal point ...but believe me I've tried every conceivable postion ...and the one which best suits ..ties with the calculated fd of the dish... Without the extended dielectric T ...there is absolutely no possiblity of getting AFN on 1 west .. But with it inserted I get a stable ..watchable picture. I guess I just got lucky ..both with the construction .. ..and with the chosen material for the dielectric plate. What is interesting is that an identical cut slab (T shaped) of identical thickness ptfe/Teflon gives about 10% less signal .. sorry for the life history .. ..but I guess I can't push any more out of my setup ..just wishful thinking. :) rgds VS [/QUOTE]

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