The PSFR, described elsewhere [e.g., Weatherwax, 1994], is a versatile receiver tuned by a personal computer which also records the receiver output. The PSFR sweeps 0.03--5.00 MHz every 2 seconds in 10 kHz steps. Since November, 1991, Dartmouth has operated a PSFR at Churchill in a semi automatic manner in which data are collected, digitized, and stored by the computer and sent back to us on a biweekly basis. Churchill is located at 58.76 degrees North, 265.92 degrees East, 69.2 degrees invariant latitude, and midnight MLT occurs at 0635 UT.
The tunable DCR translates the received signal to baseband allowing the output to be recorded on standard 90 minute audio cassette tapes with ~12 kHz bandwidth. The operator may tune the DCR to any desired 10 kHz band between 10 kHz and 5 MHz. Audio output from the DCR in conjunction with the real time visual display of the output of the PSFR was used to tune the DCR. So that events could be matched from the two receivers audio timestamps from the PSFR were mixed with the DCR output signal and recorded onto the cassette tapes every minute. In addition, the DCR was equipped with a microphone so voice announcements about the tuning of the DCR and notes on the visible aurora could be recorded.
At Dartmouth the audio cassettes are played back into a computer from a standard tapedeck through a post emphasis analog filter to restore the signal response. A pre-recording de-emphasis is used to avoid tape saturation at high frequencies caused by the normal audio pre-emphasis. The system then provides a flat response up to 12 kHz with added dynamic range at high frequencies at the expense of a poorer signal to noise ratio. A 32 kHz sample rate is used to digitize the analog tapes. Survey sonograms of the digitized data are made for each cassette tape. Furthermore, the resulting large digital data files are split into 20 Mb sections containing roughly five minutes (312.5 seconds) of data each, and more detailed survey plots of these files are created to look for interesting events. Due to the large quantity of data only the most interesting tapes were processed based on notes made during the recordings while at Churchill, resulting in ~600 minutes of digitized data.
