In our Track dish Forum, many friends and forum member asking this question that how to select good C-Band LNB for weak satellite signals. So today I decided to check all C-Band LNBs technical specifications. I am writing these details in short language so that your time will not be waste.
If you are thinking to buy C-Band LNB and confuse which one is good for you then you should check some important information about C-Band LNBs technical specifications:
1. Input Frequency:
3.4 ~ 4.2
It is old input frequency for old satellites which giving DVB-S signals which needed lots of bandwidth 950-1750 MHz But now most of satellite moved to DVB-S2 technology which shrinks in bandwidth 950-1525MHz (3.7 ~ 4.2) because mobile towers also using same frequency as 1700MHz for 3G / 4G mobile networks. So if you will use this LNB (with input frequency 3.4 ~ 4.2) then you may face terrestrial interface problem. Your picture may freeze on some transponders which using transponder frequency 3400 to 3699.
3.7 ~ 4.2
Now all satellites start using DVB-S2 technology with minimum bandwidth. So now all new C-Band LNBs coming with 3.7 ~ 4.2 input frequency. Lots of LNB manufactures promoting these LNBs as Filter LNB.
Conclusion: You should buy C-Band LNB with 3.7 ~ 4.2 Input Frequency but keep in mind that you cannot scan transponders with frequency 3400 to 3699. (If available)
2. Noise Figure / Factor / Temperature:
Yes, everyone wants to know that which LNB is better with low noise figure or high noise figure. The LNB quality is measured in units called Noise Temperature, Noise Figure or Noise Factor. I think both Noise Figure and Noise Factor may be converted into Noise Temperature. So the lower Noise Temperature is always better but it is totally depends on your satellite gain. See how same LNB can be good or bad
For Low Gain Satellite Signals:
If C-Band LNB Noise Figure is below 13K = Very good LNB – You will get very good signals for all TP
If C-Band LNB Noise Figure is below 15K = Good LNB – You will get good signals for all TP
If C-Band LNB Noise Figure is below 17K = Normal LNB – You will get normal signals and you may miss some TPs.
If C-Band LNB Noise Figure is above 17K = Worst LNB – You will get low signals for few TPs or some TPs you may not find.
For High Gain Satellite Signals:
If C-Band LNB Noise Figure is below 13K = Worst LNB – You will get very high signals, Your STB may skip to scan All TP. If C-Band LNB Noise Figure is below 15K = Normal LNB – You will get high signals, Your STB may skip to scan Some TP. Your picture may freeze in every few minutes.
If C-Band LNB Noise Figure is below 17K = Good LNB – It is depends on satellite gain level. You may receive good signals on some TPs.
If C-Band LNB Noise Figure is above 17K = Very Good LNB – It is depends on satellite gain level. You will receive good signals in all TPs.
Conclusions: So always you should buy low noise C-Band LNB because in India most of satellite have coverage of normal or weak gain (in dB), if you are from other country then check satellite gain in your area.
3. 13/18V Voltage Switching or Dual Polarity:
First understand dual polarity or voltage switch function in LNBs. here
If your satellite receiver is transferring 13-14 Volt power to LNB then you will get Vertical signals.
If your satellite receiver is transferring 17-18 Volt power to LNB then you will get Horizontal signals.
If your LNB automatic manage this voltage switching function according to set-top box power then your LNB have dual polarity feature. You will receive Horizontal and vertical transponders in single LNB.
Conclusions : For weak C-Band satellite signals, you should always use two signal polarity LNBs (means C-Band LNB without voltage switching function) because at the time of installation in dual polarity LNB when you set signals for vertical then you may loss some horizontal transponders & if you set horizontal transponders then you may loss signals for vertical transponders. But you can set separate signal polarity LNBs as per need.
Or if satellite has good satellite signals then you go with dual polarity LNB.