What is Satellite TV for PC?

A satellite TV set-top box is a consumer electronics product that converts satellite digital TV signals into high-quality audio and video signals, allowing users to watch satellite TV programs on existing analog TVs, and to perform interactive digital entertainment, education and commercial activities.

Satellite TV set-top box

Satellite TV set-top box is a kind of

Overview of satellite TV set-top box differences

Difference between dual-polarization and dual local oscillator

Dual polarization, vertical and horizontal can be received, dual local oscillator, which can be connected to two receiving high-frequency head. Receiving programs from each other does not affect each other. If it is a single local oscillator, two machines can only watch one polarized program at the same time. What is a dual local oscillator tuner? ^[2]

There are several types of high frequency head products: C / Ku band single local oscillator single polarization high frequency head, single local oscillator dual polarization high frequency head, dual local oscillator dual polarization high frequency head and other types. Dual local oscillator tuner means that there are two local oscillator frequencies in the tuner.

Ku Ku TV head of satellite TV set-top box

The Ku band frequency range is from 10.5 to 12.75GHz, and the bandwidth exceeds 2000M Hz, which is beyond the frequency range of the receiver. In order to achieve full-band reception, the Ku dual local oscillator tuner divides the Ku band frequency into two high and low bands, namely 10.7 to 11.8GHz and 11.7 to 12.75GHz. The corresponding dual local oscillator frequencies are 9.75GHz and 10.6GHz respectively. The operation of the two local oscillators is switched by a 0 / 22kHz switch. Only one of the two local oscillators is always working, so that the entire Ku-band frequency can be transferred to the receiver. It can receive in the intermediate frequency range of 950 2150M Hz.

Satellite TV Set - Top Box Band Header

The C-band dual local oscillator tuner's dual local oscillators work simultaneously and do not need to be switched. The horizontally polarized probe and the vertically polarized probe in the tuner are respectively connected with a local oscillator. The received dual-polarized signals enter two local oscillators respectively. For example, the local oscillator corresponding to the horizontal signal is 5 150M Hz, and the output intermediate frequency is in the range of 950 ~ 1450M Hz. The local oscillator frequency corresponding to the vertical signal is 5750M Hz. The output IF is 1 550 ~ 2 050M Hz. If you turn the tuner 90 °, the IF frequencies of the two local oscillator outputs of the tuner are just opposite. In this way, the dual-polarized C-band signal in the range of 3.7 to 4.2 GHz can be converted into an intermediate frequency signal of 950 to 2050 M Hz and output at the same time, without 0 / 22kHz or 13 / 17V switching. The purpose of doing this is mainly for the convenience of engineering use, because it is not necessary to make the dual-polarization feed and two high-frequency heads, and only one cable (also dual-cable) can output horizontal and vertical dual-polarized signals . The prerequisite for using this high frequency head is: the IF bandwidth of the receiver must be in the range of 950 ~ 2050M Hz to ensure that the program is not missed. With this tuner, for analog satellite TV receivers, as long as the receiver has

It is wide enough to receive dual polarization signals with or without the dual polarization switching function. This is very suitable for early machines that do not have the 13V / 17V switching function. However, it is more troublesome for satellite digital TV receivers. Because the two local oscillators work at the same time, we must first understand the local oscillator frequencies corresponding to the two polarization directions. The vertically polarized signal is connected to a high local oscillator of 5750M Hz (of course, the opposite can be reversed, as long as the high frequency head is turned 90 °), then when setting the receiver parameters, pay attention to set the horizontal signal local oscillator to 5 150M Hz, and the vertical signal local oscillator The frequency is set at 5 750M Hz. As for the polarization method in the parameters, it can be set arbitrarily, and it has no effect on the reception, so that the dual-polarized signals can be collected.