EINMUF: An HF MUF, FOT, LUF Prediction Program

Abstract : This work describes a FORTRAN algorithm, called Subroutine EINMUF, which predicts the Maximum Usable Frequency (MUF), the Frequency of Optimum Transmission (FOT), and the Lowest Usable Frequency (LUF) on a specified HF communications path. A single call to EINMUF produces up to 24 predictions at hourly intervals starting with a specified day-time group DTG. MOF calculations are made with the NOSC MINIMUF85 MUF-prediction program using the first available sunspot number SSN from the following list: (a) an effective SSN derived from current oblique-incidence sounder data; (b) a 5-day running average of SSNs derived from solar 10.7 cm flux measurements or direct SSN measurements; (c) an effective SSN determined from old sounder data; (d) SSN extrapolated from previous SSN measurements by the McNish-Lincoln method; (e) SSN derived from a mean-value representation of the 11-year solar sunspot number cycle. Keywords: Electromagnetic compatibility; High Frequency(HF); Ionospheric propagation; Propagation prediction; Sounder updating.