LNB Frequency explained

This will hopefully shed a little light on what the LNB frequency should be set at.

First, the LNB on the dish acts like a mixer / amplifier and your FTA receiver operates between 950 Mhz and 1450 Mhz. So knowing this, you need to select a LNB frequency that when mixed with the transponder frequencies will give a difference frequency of between 950 Mhz and 1450 Mhz that your receiver can use.

Example; the satellite at 118.8*w operates between 11.7 GHz and 12.2 GHz. If you beat those frequencies with a LNB frequency of 10.750 GHz the resulting frequencies will be the two original frequencies plus the sum of both and the difference of both. With Ku band we're only concerned with the differential frequencies.

In this example, on the low end, we have the transponder frequency of 11.7 GHz minus the LNB frequency of 10.750 GHz which leaves you with a resulting differential frequency of .950 GHz or 950 MHz, which is the lower end of the frequency range your FTA receiver can use. If you calculate the upper end, take the 12.2 GHz minus the LNB frequency of 10.750 GHz and you have 1.45 GHz or 1450 MHz. As you can see by beating the incoming TP frequencies with a LNB frequency of 10.750 GHz allows the whole block of transponder frequencies to be sent to your FTA receiver between 950 MHz and 1450 MHz.

Now that we know that, let say we want to select a LNB frequency for a satellite that operates between 12.2 GHz and 12.7 GHz. First the low end. We have a TP frequency of 12.2 GHz but it has to hit the receiver at 950 MHz. 12.2 GHz minus .950 GHz equals 11.250 GHz and that would be the LNB frequency for that satellite. The upper end would be 12.7 GHz minus 1.450 GHz ( 1450 MHz )which again would be 11.250 GHz. So in this case the LNB frequency turns out to be 11.250 GHz.

With C-band it works the same except you're beating the LNB with a frequency slightly higher than the received TP frequencies which makes it seem backwards. ( With Ku band you're beating the TP frequencies with a slightly lower LNB frequency. )

Example; a C-band satellite operates TPs between 3.700 GHz and 4.200 GHz. to be able to receive all of the frequencies you'll need to have them again between 950 MHz and 1450 MHz so your receiver can use them. Taking the low end first 3700 MHz plus the 1450 MHz your receiver needs equals 5150 MHz and the high end would be 4200 MHz plus the 950 MHz your receiver needs which again equals 5150 MHz. So in this case the C-band LNB frequency would be set to 5150 MHz or 5.150 GHz.

end c/p....
thnx to unknown author