Propagation of HF radio waves on short high latitude paths

The joint use of experimental data and modeling methods on the high-latitude Gorkovskaya-Lovozero path with a length of D ~ 900 km made it possible to test several methods for determining the maximum useable frequency using the IRI model: 1) ray tracing method, 2) Smith method. In the latter case, the propagation coefficient MD(IRI) was used for the path length D and various options for determining the critical frequency foF2 in the middle of the path. The results relate to the conditions of minimum solar activity (May 2017-January 2018). It was found that the second simple method using the original IRI model yielded a result comparable to the result of the ray tracing method with model adjustment to the full set of vertical sounding data. The method of using the total electron content, which proved to be good under conditions of high solar activity, led to significantly underestimated results.