Can u run with just a sat hooked to the Rud input and not one hooked to the normal sat connection?

No, it is not possible, because satellite in the unit is treated as primary. Without primary satellite it can't work.

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Spirit System developer

The reason I ask is because I am continuing to troubleshoot a problem with seeing intermittent signal loss and sometimes the light on the sat will come on but nothing works. None of the servos will move when the radio sticks are moved. I wanted to hook just a sat to the rud input to see if there is a problem with the primary sat input. I have replaced the sat and cable still the same problem. The radio works fine on my other helis that have spirit units on them.

It seems that your primary satellite (connection) is not good. If you can see that both lights are On and you have no response when moving with the sticks then the problem is there.

Spirit will not work until there is signal on the primary satellite input as protection so you can know that there is something wrong.

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Spirit System developer

Yes both the red light on the spirit is solid red and the light on the sat is solid. Again I have already replaced the sat and cable. So it sounds like there is a problem with the primary sat input. If so what do you suggest?

"Spirit will not work until there is signal on the primary satellite input as protection so you can know that there is something wrong."

I think its not so good....

So if in flight, somehow the primary satellite cable break, the spirit won't react to command, and crash the heli, rather then using the second satellite which works correctly?

Of course not.
This apply only for initialization process. Then primary satellite connection can fail and it will still work from the secondary.

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Spirit System developer

So back to my question. It looks like I might have a bad sat input. Anyway to test it? Also when the light goes on solid on the sat does that mean that it see's a radio signal from the transmitter? Right now I have zero faith in this unit. Will not fly it until this problem is resolved. This problem maybe the cause of me destroying my goblin 380. Total rebuild.

We can check your unit and fix it if we will find any problem.

Was the cable that you have changed different one?
We know about many cases when new Spektrum cables were faulty and sometimes loosed its connection.
These connectors and cables are very fragile so you can't even pull it with any force.

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Spirit System developer

The cable I used to replace the original one was brand new. I guess I could try another one. Do you have any suggestions for a better cable to use? Going back to my other question, when you have a solid light on the sat does that mean that it is seeing the transmitter? If that is true then normally it would then pass the signals to the spirit unit. Correct? Just trying to understand how it works.
Thanks