Dish Size increase when Multiswitch used

championc

Hi all

I am involved with a community in Spain and in order to receive BBC's and ITV's, a 1.8m dish is required. One owner has their own 1.8.

Current 1.2m dishes need to be upgraded to the larger size but have Quattro lnb's into Multiswitches. Given that a multiswitch introduces loss, how much bigger would a dish need to be to cater for this loss ?

Most blocks have either 5x8's or 5x12's. I assume that most multiswitch have in or around the same loss levels.

The current 1.2 dishes work fine for Sky channels on the European spot beams.

Thanks in advance

Apogee

Hard to say, as it depends on how much margin you have on the existing setup e.g. do the channels break up in light rain, or are they still steady in heavy rain. If the latter, then the dish is probably fine for a multiswitch.

There is a very good set of 3 articles first published in Television magazine by Bill Wright
http://www.wrightsaerials.tv/articles/index.shtml

Bill Wright wrote:

The dish — how big?
On a small system the only active satellite IF component between the LNB and the outlet sockets is the polarity switch. A small system like this does not need any other satellite IF amplification. Although the switch amplifies the satellite IF signals a little to compensate for internal splitter losses it adds very little noise, so the c/n ratio is only slightly worsened (there will be more about c/n ratios later in this article). This means that we can use a dish and LNB combination that provides a relatively modest c/n improvement compared to a standard Sky minidish. In areas where Sky recommends the smaller minidish (roughly south of a line from Liverpool to Newcastle) a good quality 65cm dish is perfectly adequate for a small distribution system. Further north a 75cm or 85cm dish should be used.


C/N & LNB
Even if the c/n ratio is subsequently reduced during further amplification the figure obtained from the LNB will continue to have a direct bearing on the c/n ratio at the final outlets. It should be possible to obtain BER readings at the LNB ranging from 2.0 E5 to 6.0 E6.