ok,
I have one of these devices (an antenna noise tuner). its called a Palomar tuner-tuner (no longer made from what I hear).
this device sits between your antenna tuner and the radio. 

The basics: you use the noise bridge to tune the antenna tuner to minimum noise (the quieter, the closer to resonance you are).

How I do it:
1. tune to the desired frequency in AM mode
2. turn on attenuator or reduce RF gain to 50%
3. turn on the noise device
4. adjust inductor for closest band (setting a or b for 10 meters, etc.)
5. adjust input capacitor for lowest noise
6. adjust antenna capacitor for lowest noise.
7. repeat steps 5 and 6 until noise is reduced to almost nil (or as lo as you can get it)
8. turn off device, turn up RF gain and set desired mode.



I use the palomar tuner-tuner to retune my antenna for optimal efficiency on any band. I also record the settings so that I can get close the next time (reduces tuning time).

Unfortunately, the tuner-tuner unit is no longer manufactured. I wish that MFJ would make something similar. 

This is the cheap alternative to an expensive auto-tuner for your HF radio. It also has the advantage of allowing you to tune the antenna without having to key the transmitter (thus causing unintended interference) and saving wear and tear on the finals of your radio.
The reason I use AM to listen is that it gives the best noise figure, thus making it easier to find the resonance dip.

anyway, there is my tutorial for using a noise bridge to tune an antenna with a tuner.

DE N7zzt - eric.