RX-Set PLL for QO-100

With the QO-100 RxSet the manufacturer DXpatrol offers a modified LNB plus a power supply and a 25 MHz clock source. The LNB used to have two outputs. One of the outputs was modified to act as an input for a 25 MHZ reference local oscillator clock. This greatly improces the frequency stability, as required for narrow band signales. The output signal of the LNB is a 740 MHz after down conversion. This receive signal is fed to a suitable recceiver,(not supplied) for example the DXPatrol SDR.

The PLL/Bias-T component has the following functions:

• Supply of the LNB with the operationg voltage (Bias-T)
• Impedance matching from 75 Ohm (LNB) to 50 Ohm (SDR UHF receiver)
• 25 MHz oscillator clock to modified LNB
• Optional 10 MHz input for external precision clock source (GPSDO or similar)

The connectors towards the LNB are "F" sockets, the 740 MHz IF signal towards the SDR receiver is available on an SMA socket. The 10 MHz ref clock input is also an SMA socket. This reference clock input is optional, and should be supplied from a high precision 10 MHz source, for example a GPS disciplined oscillator (GPSDO) or other source. When injecting a 10 MHz reference the internal PLL is clockled by this signal instead of a quartz oscillator, the result is a much better stability and a cleaner signal due to a better signal to noise ratio.