Tech Notes from the Field

Talking with a colleague there appears to be some confusion on what a LUT is.  This is referenced in the new procedures when upgrading to version 2.7 of the software.  To be honest, with our NV20’s we do not even have saved LUTs.  If your transmitter is running IBOC with either FM+HD or HD only it is recommended that a LUT is saved.

The instructions provided with your 2.7 update will take you through the recalibration process.  We performed ours BEFORE the revised procedures came out.  Overall ours went well except that one transmitter lost its Transmitter High RF Drive Power threshold.  Huh?  Yes, we had to manually set the threshold level again so we could make full TPO.  A minor annoyance considering how complicated this box is.

I’ve read the new procedures which includes the reset of the LUT.  Again, the LUT is a look-up table.  If you have one configured, located under Hardware Settings, it contains information on the mode (FM+HD or HD only), TPO, and frequency.  The location number is what is referenced in the Preset under Other Audio.  The LUT height is figured out to compensate for any overshoot (power) when the transmitter is turned on.  In addition the ramp up time or the time it takes the transmitter to achieve full power is indexed and is the LUT gain.  Once the height is set, you work the gain to achieve a nice smooth ramp up to full power.

The bottom line is the LUT is used as a reference and target for a preset running an HD mode.  If you are running FM Only, the LUT is not required or important.  The transmitter references the LUT and then powers up smoothly and stops at the desired TPO.  If you run two presets with differing power levels it is recommended you create a LUT for each one.  The information is then stored in the exciter.

That is my understanding of the LUT.  Hopefully this clears up some confusion on the purpose.  As I learn more I will modify this post.

Cheers!