how does lnb convert frequency reception?

at present, the working frequency of network tv reception on the market is mostly 950-2150mhz, and some characteristic models are 950-2050mhz. therefore, the frequency of satellite signal received by the high frequency head must be within this range after conversion. so how does the high frequency how does lnb convert frequency reception?

it's a simple subtraction operation, but the ku band algorithm is different from the c band algorithm. for ku band, the downlink frequency is used to subtract the local frequency. the difference between the two is the converted frequency, which must fall within the working frequency range of the receiver. for example, a pbi-1040 high frequency head is used to receive 12730 groups of 76.5-degree stars. its local frequency is 11300, and its output frequency is 12730-11300 = 1430, falling into the range of receiver operating frequency 950-2150, and the program can be received.

but it can't be used to receive 113 degree stars. the downlink frequency of 113 degree satellite's main program is 11132, so 11132-11300 = - 168, which is beyond the working range of the receiver. in general, the dual local oscillator is used to receive 113 degree stars, because its low local oscillator 9750 can meet the requirements, while the single local oscillator 9750 is very rare on the market. on the other hand, there will be problems when using the dual local oscillator high frequency head to close the 12730 group of 76.5. the high local oscillator is generally 5374142730-10600 = 2130, and some machines cannot. the algorithm of c-band and ku band is just the opposite. it uses the local oscillator of the high frequency head to subtract the downlink frequency.