Frequency options (handbook)

The main channel of THERA operates in either of 2 frequency (bandpass) ranges:

Note:” bandpass” is short for “bandpass filter” and is what is used to limit the information / oscillations that are used (i.e., passed on by the filter) to specific frequencies within either of the two following bandpass frequency ranges. As a helpful analogy, bandpass filters are also used inside AM or FM radios to make it so you can listen to only one station at a time.

• Low “deep” frequencies (LDFs) starting from 1 Hz up to 25 Hz with digital setting (orange LED cursor and scale on the linear frequency display). Note: this could be compared to the AM frequency band on a radio.
• Higher, more “normal” or “standard” frequencies from 10 Hz to 250 kHz (green LED cursor and scale on the linear frequency display). Note: this could be compared to the FM frequency band on a radio.

Within each of these bandpass frequency ranges, there are the following further options:

• No bandpass filter/ “All Frequencies”: oscillations of all different frequencies are passed by the filter and done so all at the same time. This setting actually applies equally to both bandpass frequency ranges. For either of these bandpass frequency ranges, information/ oscillations from 1 Hz on the low end to information up to 400 kHz on the high end is used. Imagine listening to all radio stations, in both frequency bands at the same time! Note: this mode is indicated on the linear bandpass display by either the orange or green cursor being “parked” on the extreme right end.
• Fixed narrow bandpass filter without “wobble”: oscillations of only a certain frequency are “passed”:
• Fixed narrow bandpass filter with “wobble”: oscillations around a certain fixed center frequency are passed but one at a time in a sweeping back and forth fashion:
• Narrow bandpass filter sweep (of the full range): oscillations are passed, one at a time, in a sweeping back and forth fashion across the entire range of the selected frequency range: