On 19/05/2011 20:31, Herbert Graf wrote:
> Perhaps I'm missing some other factor, but a common thing in radio
> design is that whatever you signal source is, that's where the majority
> of your amplification should happen.
>
> At your signal source is where the highest SNR will be, if you put your
> amplifier in the middle of the cable then you'll be amplifying a much
> higher amount of noise, which doesn't help much on the receiver end.
>
> Again, this is all based on there not being some other reason making
> putting the inline amp in the middle of the run a better idea.

You are correct for Professional line drivers.

The cheaper ones overload at the LNBF!

Really only the professional ones with a switch to set type & length of=20
cable for correct equalisation are any use. The cheap in-line ones with=20
no settings are useless as the 950Mhz may overload when the 2100MHz is=20
amplified enough.

Using the heavier cable up to 60m is a simpler solution. (CT125 / PF125,=20
a 1.25mm centre core instead of 1mm, thus overall cable is fatter to=20
keep impedance 75 Ohm. Hydrophobic foam dielectric is more robust than=20
semi-airspaced).  Actually may be fine up to 80m on Sky Brazil as only=20
the lower part of IF is used.


A bigger dish is best way to get better SNR! Distribution systems always=20
use next size up of dish. Too big a dish creates different problems.=20
Especially in Europe where 4 or more satellite may be "co-located" on a=20
small dish, but separate on a big dish (28.2 Astra 2A, 2B, 2D and 28.5=20
Eurobird 1)


--=20
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