Since 22KHz in auto mode does work for port 1 (LNB 1), I can't think of why the same setting not work for all other ports. However, I just tried with 22KHz off and the situation is still the same - LNB 1 (port 1) works but none of LNB 2 (port 2),.., LNB 4 (port 4) work, even though there was only one LNB connected to one of the port on DiSEqC at all time.
I think I have correct port (LNB) settings. My receiver PROSAT P-8800 has three places affect LNB settings.
1. Setup menu - to set Hi/Low freq. for each LNBs.
2. Add New Transponder menu - to select which LNB is to be used for each transponder frequency.
3. Satellite Selection menu - to select which LNB is connceted for a selected
satellite dish.
Any other suggestions? After trying every possibly set up combinations, I am more and more leaning toward bad
DiSEqC switch. It will be great if someone can instruct me how to use a simple machine (e.g. a voltmeter?,...) to test each port on the DiSEqC switch directly to verify whether they are bad. Thanks mcuh for all the help!