I have spent the greater portion of many nights looking upward at the dynamic horizon to horizon sky-filling displays of aurora when the northern lights were very active. Natural ELF radio is one of the ways of monitoring for this activity. However, if other signals have been modulated by this interference, the resulting sidebands will not be notched out. Therefore, receiver linearity is very important in a Natural ELF Whistler Radio to prevent generating modulation cross-products. A band pass filter that would pass every thing from 0.5 to 7-kHz may be the most useful for monitoring most of the whistler frequencies.
Some spectrographs are difficult to use when the time and frequency are hard to decipher.
Extremely accurate time can be obtained from hand held GPS receivers if you use one that has an external signal connector. Remember, whistlers only come from lighting. Viewing the global weather reports on TV, or on your computer, may allow you to find when electrical storms are forecast for the area of the world existing at an equal latitude in the hemisphere opposite to yours and existing on the same magnetic longitude as yours. If lightning is not occurring there, such as in one of the great desserts of the world where it never storms, then do not expect any one-hop whistlers. Of course there is still the possibility of receiving two-hop whistlers if an electrical storm is occurring in your region.