A UK Sky satellite dish receives signals at approximately 10.7–12.75 GHz, but the LNB (Low Noise Block downconverter) on the dish converts these to much lower frequencies before sending them down the coaxial cable to the Sky receiver.
### Frequencies used
| Signal | Frequency |
| —————————— | ————– |
| Satellite downlink (Ku-band) | 10.7–12.75 GHz |
| LNB low-band local oscillator | 9.75 GHz |
| LNB high-band local oscillator | 10.60 GHz |
| Output down coaxial cable | 950–2150 MHz |
The output is calculated as:
f_{\\mathrm{IF}}=f_{\\mathrm{satellite}}-f_{\\mathrm{LO}}
For example, a satellite signal at 11.5 GHz with a 9.75 GHz local oscillator produces:
11,500 − 9,750 = 1,750 MHz down the coaxial cable.
### Important for radio astronomy
The coaxial output range of 950–2150 MHz includes the 1420.405 MHz hydrogen line.
However, the LNB does not receive hydrogen-line radiation at 1420 MHz directly. It receives Ku-band radiation and converts it into that frequency range.
A few other points:
* Standard universal LNBs use 13/18 V for polarisation selection and a 22 kHz tone for high-band switching.
* Sky Q wideband LNBs operate differently and typically output approximately 290–2340 MHz.
* The coaxial cable also carries DC power to the LNB.