DTH (Direct to Home)
DTH means direct to home basically this service is alternative of cable TV. It is the distribution of television signals from high powered geo-stationary satellites through a small dish antenna & satellite receivers in home across the country. This service works on K U band (14/12 GHz)& are fully digital.
- The main advantage of KU band satellite broadcasting is that it requires physically manageable smaller size of dish antenna compared to that of C band. C band requires 3.6m PDA (14db gain at 4GHz) while KU band requires 0.6m PDA (35db gain at 12GHz).
- DTH reception requires a small dish antenna 60cm or 90cm, which can be easily mounted on the roof top. Feed along with low noise block converter & set top box (integrated receiver decoder, IRD) with CAS(conditional access system). A bouquet of 40to50 video programs can be simultaneously received in DTH mode.
- DTH uplink chain the sources are feed to a router & output are divided into A, B&C group. Each group contain two video sources .All group are multiplexed digitally (QPSK) modulated individually at 70 MHz IF. Each group is further doubly up converted at L band (950-1450MHz) at KU band (12-14GHz). A, B&C group up converted to KU band streams RFA (13891MHz), RFB (13895MHz),& RPC(13839MHz)& are individually amplified using Klystron high power amplifier(KHPA).
- DTH Downlink chain consist of a dish, LNBF & RF cable, set top box. RF waves (12/14GHz) from satellite are received up by a level converting into electric signal. The electric signal is amplified and down converted to L band (950-1450MHz) Feed & LNBC are combined in single unit called LNBF. The L band signal goes to indoor unit. The set top box or IRD (integrated receiver decoder) down converts the L band signal to 70MHz IF signal performs digital demodulator, demultiplexing, decoding and finally gives audio video output to TV for viewing.
- The only drawback of KU band is that the signal attenuates during rains.