Polarization Coupling Loss & Sea Gain Effects in the Ionospheric Propagation of Medium Frequencies

315-318Polarization coupling loss and sea gain are the two important ionospheric factors which have major effect on skywave attenuation of medium frequencies. The Research Department of All India Radio (AIR), New Delhi, have made nighttime field strength measurements on a number of mf circuits over the past several years at Delhi and for over 1 yr at several other centres of AIR. Data thus collected on 32 circuits have been analyzed with a view to investigate the effects of coupling loss and sea gain as applicable to lower latitudes and the results are discussed. Analysis of polarization coupling loss has indicated the following. (i) Polarization coupling losses do exist in our latitudes. (ii) Even in our latitudes the losses are more for circuits in lower latitudes as compared to those in higher latitudes. (iii) The losses are maximum for circuits whose direct ion of propagation is east-west and go on reducing as the direction changes and become negligible when the direction of propagation is north-south. (iv) The losses estimated as per formula given originally in 1964 by Phillips and Knight [Phillips G J & Knight P, Proc. IEE. 112 (1965), 31] are Jess accurate and higher than the measured values as compared to those estimated by using the formula given by CCIR in Report 575, (CCIR Rep. 575, Vol. VI, International Telecommunication Union, Geneva, 1975), which are closer to measured ones. As regards sea gain it is found that estimated fields using CCIR method but ignoring sea gain factor are nearer to the measured values