lnb conversion gain calculator

[beigas]

re *

i'm a newbie in c-band, but i have just received a used d 6ft dish and now i'm looking to add one c-band to my ku-band fleet.

so i am looking on ebay to purchase a c-band lnb and i can select one with 65 or 70 db conversion gain, and i cannot find out which one i have to use. i didnt find any calculator or formulas how to determine what i need. maybe any1 can help or suggest something.

as far as i understand adding dielectric plate to receive a circular polarised signal makes about 3 db signal loss.

i want to receive 40.5w with circular polarisation, at my location eirp is 39 dbw (from ses.com) or 37 dbw (from satbeams.com), dish size is 6ft.

thanks in advance!

 

[Magic Static]

to SatelliteGuys beigas I don't know if you would be able to tell the difference between those LNBFs. Here lately a PLL LNBF has become available and we like it.
http://titaniumsatellite.com/c1pll

 

[beigas]

i see this is 65 db conversion gain lnb. what are eirp value, signal polarisation, dish size, and signal strength and quality when you are using it?

 

[Magic Static]

I don't use a C-Band LNBF. I have a dual orthomode feedhorn and 4 PLL LNBs On a 10' dish. If I needed a LNBF I would buy that one though.

 

[beigas]

there are 3 lnb's with similar price (about $20) available in ebay - DMS international BSC421, WS international ESX241 and WS international DMX241. i dont see any difference in technical parameters except conversion gain value, and i'm sure they all are made in china maybe even in the same factory

which one have i to choose?

 

[Magic Static]

They are all pretty much the same. Buy the cheapest one. Good learning experience.

 

[beigas]

thanks!

 

[richyrich]

I have a system calculator that uses dish, lnbf, cable, receiver, satellite transponder being received, and your location on earth comparitivly to "ThE Installed perfection of each component". As a system the lnbf shows you on the receivers meter signal strength's; which is a composite of system gain; the. Bigger c band dish; more final composite signal of transponder. Gain by just the lnbf depends on size and focus of the dish/lnbf combo, the more the "system" gains from a direction these are also adjusted in the lnbf using attenuation resistance and capacitive functionally llocked down to a certain "derived product" of the final lnbf output; which is stable at the freq. it is selecting, and then the cable length of that part of composite signal.

now is where this becomes tricky because of something called noise. Today, the sources of noise that Factor in on systems are renounced as hogpits with derivatives.

1) empty space is noise

2) another satellite nearby is noise

3) same frequency as composite is noise

4) nearby frequencies are noise

Each factor must be within certain margins; in order to not effect any one part of the system as a whole; which is the fcc and signals in general.

your dish size, focus, and installed placement of the dish has a huge factor in the noise category; and finalizes everything the formula means. The NOISE is shown on your better meters as S/N (signal to noise ratio) ...

10 foot dish gain w/ 2 degree sat spacing and 2 degree 1st sidelobe = 43 db of gain

normal lnbf = 50 - 65 db gain

added to satellite lobe (-) of say -125

equals lets say = within receivers -35