Q1:

Can I just install one input of the Zinwell 3x4 multiswitch?

A:

No. You have to use both input 13V and 18V of the switch for 101° satellite. Otherwise, you will lose either 13V or 18V side of signal.
For more detail information, please see SAM-3402

Q2:

There are two cables from the dual LNBF, how can I know which one is 13V or 18V.

A:

There is no difference for both cables from the dual LNBF. Therefore, either of these 2 cables can go into either 13V or 18V input of the switch.
For more detail information, please see SAM-3402

Q3:

If I have less than 4 receivers, can I connect them with any outputs?

A:

Yes. You can connect any output of the SAM-3402 to the receiver.
For more detail information, please see SAM-3402

Q4:

Do I need to use the terminator for those unused output ports?

A:

Yes. It is suggested to connect the terminators to the unused output ports when the off-air signal is also connected.
(CAUTION: The 75 ohm terminator can ONLY use for SAM-3402 but NOT to use with SAM-4803, SAM-4402-3A, SAM-6802, WB68 & WB616).
For more detail information, please see SAM-3402

Q5:

If I need more than 4 outputs, how can I do?

A:

You can use Zinwell 6x8 multiswitch WB68.
These 8-way switches are designed for when 8 or more receivers are used.