Low Noise Block downconverter or lnb and its types

This thread is complete guide to lnb or Low noise block downconverter and also we explained its types. Actually this device is related to satellite TV users, lnb satellite setup, and also use to subscribe a satellite dstv. It is always located on the front of satellite dish. Working process of the device is related to satellite signals and converting them into lower bands. It receive the signals from satellite and which are low level microwave so it coverts them into low level frequency bands also amplify them and then transmit them to the satellite receiver which is located indoor. The power is sent by receiver to this device for working. Power is sent by using same cable that is used to send signals to receivers by this we don’t need a separate cable for power.

The term low noise term used in name is related to quality of transistors located in device which works as first stage input amplifiers. The unit in which quality of lnb is measured in Noise temperature. Other alternatives are noise factor or noise figure. They both can be converted to noise temperature. So how the quality is measured? Answer is lower the noise temperature higher is the quality and higher the noise temperature lower is the quality of device. For example if an lnb device have the noise temperature 100K and second have the 200K than first is twice good from second in quality. Devices with c band are better than Ka band due to lower noise temperature. So I suggest c band devices for better results.

The block term used in name is related to conversion of frequencies from microwave to lower block or ranges which are received from satellite. The range of satellite broadcast is from 4 to 12 to 21 GHz.

Polarization :

Polarization is a process through which they can transmit more TV channels using minimum given frequencies. But then this process required special receiving equipment for receiving signals which then filter the incoming signals on base of polarization.

The probe inside the Lnb devices only receive those signals that match the plane of probe. So for maximizing the strength and minimizing the unwanted signals probe is set or aligned with polarization of satellite signals. This can be set by adjusting the LBN’s skew and rotating it along wavelength axis. Some times for better results polarizer is fit in front of LBN’s mouth but these polarizers are rarely used now a days.

Types of lnb device :

C band LNB :

Here is example of a C band LNB device and properties are following:

• 5.15 GHz of Local oscillator.

• Frequencyrange is from 3.40 to 4.20 GHz.

• Noise figure or noise temperature is from 25 to 100 kelvins.

• Linear Polarization is used in this device.

Ku band LNB :

It is a Standard North America Ku band LNB which have following specifications.

• Local oscillator of 10.75 GHz band.

• Frequency ranges from 11.70 to 12.20 GHz.

• Noise figure is 1 dB typically.

• Polarization used in device is Linear.

Dual band lnb device :

Ku band LNBs mostly use two type of alternative local oscillator frequencies like 9.75 GHz to 10.6 GHz also having the higher frequency option can be selected using 22 kHz tone by injecting into cable. These devices can used to receive high bands of 10.7 to 11.7 GHz while using lower bands of 9.7 GHz LO frequency also higher band of 11.7 to 12.7 GHz can be received using 10.60 GHz LO frequency. Some of Ku band lnb devices can have 4 local oscillator frequencies.

Quattro lnb :

This is a special type of LNB planned for use in a commonor shared dish setup to carry signals to any number of TV tuners. A quattro lnb has anonlyone feed horn and four outputs, each one of themstream just one of the Ku sub bands.Although a quattrousually looks similar to a quad lnb, but it cannotbe connected to receivers directly.

Tags : Lnb, Low noise block, low noise downconverter, Quattro lnb, types of lnb