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lnb voltage level

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Ex Member
Ex Member

Jun 29th, 2008 at 7:59am  
How can I optimize my LNB voltage level. It is recommended by the installation guide to start with an initial level of 21V. Should I go then to 18V if I have signal or is there a procedure how to find the right voltage.

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Eric Johnston
Senior Member

Posts: 2109
Reply #1 - Jun 29th, 2008 at 9:20am  
Follow whatever instructions are in your installation guide.

Many dual polarisation Ku band LNB-Fs (incorporating a feed horn), as used for satellite TV reception need a switchable 13 or 19 volt supply which remotely changes the nominal receive polarisation.  Such LNB-Fs often also have an option to change LO frequency using a 22kHz tone (e.g. 9.75 or 10.6 GHz).

If you have an extremely long LNB cable and need 19v at the LNB you need to be aware of the voltage drop along the cable, especially if you have one or more L band booster amplifiers along the cable (e.g. 200 m long cable).  In such a case you need a temporary T connector at the LNB so you can measure the voltage while  the LNB is connected.  I've found suitable T adaptors with 3 BNC sockets and used a pair of BNC plug/F connector adaptors to join the cables.  This is only suitable for use while testing the voltage, not for operational service.

Most VSAT LNBs have fixed local oscillator frequency and the DC supply volts does not affect the LO frequency.  There are some VSAT LNBs however where the DC supply volts switches the LO frequency.  If a VSAT LNB has a rectangular waveguide input flange the polarisation is set mechanically by you.

BUC/LNB transmit /receive integrated assemblies (TRIA) are now beginning to appear which have options to remotely change the LNB local oscillator frequency and change between co-pol and cross-pol operation using voltages/tone.

Best regards, Eric.
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