no, .2 meaning 0.20 and .4 meaning 0.40 would be more separated that what the picture shows. on top of that 0.42 would be closer to the LNBF edge (as per chaparral the feed edge is almost flush with the scalar) or openning than 0.2 (if a feed with a 0.2 setting even exist, the lowest f/D ratio for a Dish i have read or heard is .275). more likely they represent .32 .34 .36 .38 .40 and .42. The reason I ask is to compare to my gospell , unfortunaelly (or fortunaelly) it works very well but in a position where if pendragon sees it he will have a heart attack!, lol. The LNBF is All the way in and can not go in further because the C LNB hits the scalar and it is not even straight and that is what bothers me even more!. It is driving me crazy now all this but heck even LPBS works at night if I bump the dish upwards just a bit. I guess the Gospell LNBF has its focal point way inside its throat!!! (it acctually has another one half way but 8PSK ku reception is not as good as a 90 cm dish so I kept pushing it inside)
icu1954. f/D can be calculated but more likely your dish documentation has that value or you could find it on the internet using the dish model number. f = D * D / 16 * c where c is the distance from the dish center plate to the imaginary line that goes from edge to edge . D is the diameter and f focal length. all measurements have to be taken using the same metric system , either international or US. i go by memory so maybe i am mistaken , please check it online.
As per chaparral (valid for chaparral feeds that is) the focal point of the feed is just 1/8" away from the feed openning. So you will have to adjust the feed 1/8" "edge" to match the dish focal length. every feed is different as it depends on its geometry (pyramidal type feeds has their focal point even further inside). the focal point of a dish is always meassured from the dish center and perpendicular to it. unfortunaelly i do not think this LNBF's have any documentation that clearly states where its focal point is , at least not my Gospell. you are lucky yours at least has f/D ratio markings , mine barely has the skew setting and it is 90 degrees off!, lol. I am not good with the US metric system and probably 99% of the world isn't either!.
To adjust the feed to match the dish focal point you can not move the feed in an out , it has to be the whole Scalar/feed assembly because the Scalar has to be set for .38 always (it determines how wide the "illumination" angle is) and that is why pros like pendragon fabricate custom feed arms or holders that allows them to move the scalar/feed together in or out. but in any case trial and error has always been the best friend of the americans since the first immigrants arrived to this land so keep trying till it works best no more.
I do not think right now there will be an 8PSK signal on Ku that I can not watch (other than LPBS at night) with the 6 footer / gospell C/ku LNBF combination but will have to wait a bit more since I just adjusted the feed very recently. As per C band , Africa Channel on 133W comes in fine and Fox Sports HD en Espanol on 55.5 W as well plus any 8PSK with a 3/4 FEC or lower. I get some 5/6 8PSK's but I dont think I get all , higher FEC are a no go so far. no problem with the highest DVB-S FEC's signals and no problem with cross polarisation anywhere (probably 58W most critical since it has to equal signals on different polarities). Obviously it is just a 6 footer so adjacent interference is an issue but signal strenght or quality wise it performing great. I dare to say that even better than most 8 footers out there.
What i am trying to say and insist on is that the most important factor is not the LNB's specs but rather the dish mount aligment and even more critical the feed/lnb aligment as well. most people have issues due to poor aligments not because they use LNBF's made in china or because the dish size (heck back in havana the feed horn was acctually a popular oil metal can that contained vegetable oil that Italy had donated to Cuba and its size was a perfect match for a 2.4 Ghz MMDS service that had 11 analog channels for Havana hotels, ESPN, HBO , Cinemax , CNN and the likes).
Of course once you peak your dish to the maximum I bet we will all want bigger dishes or Norsat's LNB's and Chaparral ortho feeds to get that other fringe signals we dont get due to phase noise or not enough gain.
