I understand the Null Mod, but the Null control on my 9748 appears to do nothing... Anyone have some insight into this?

Hi Alex,
What's the "null mod"?? link(?)

"Nulling" usually refers to nulling the carrier;
i.e. making for minimal carrier bleedthru.

I am only familiar with the 4710 and the 9710 balanced modulators.

If U are hearing the carrier, it's possible that U have a very weak carrier signal(?).
Try using a preamp with a gain of 2 or 4.

Two of the things I liked about the 4710 was that 1) it had a gain control and 2) it had a LED overload indicator. Feed in a signal and adjust the gain until the LED lit, then back off until LED goes out. This maximizes the signal into the 1496.

T

There is a trick to tuning these knobs in properly. You can start by centering both knobs, applying a signal to just one input and tuning the other one until the sound dissappears. Then swap inputs but don't touch the first pot you tweaked, just turn the second one until the sound again dissappears. At this point you are nulled and should have a balanced modulator as opposed to an unbalanced one (where the original signals come through as well as the sum and difference). I'll have to get a module in front of me if you need me to expand further, but this is the basic idea.