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where λ = 300/f – the wavelength of communication, m; f – frequency of communication, MHz; Gε – coefficient of strengthening of the reception antenna at a working frequency in the direction of arrival of a wave; RA, XA – active and jet components of entrance resistance of the receiver, Ohm (the jet component of entrance resistance of the receiver is accepted equal to zero). Taking into account a formula 2 we have:

Using the set frequencies for calculation of a radio communication terrestrial waves (7,2; 7,5; 7,8 MHz) at d=d1+d2 =80+20=100km, and having taken as the transferring Sht-10m antenna as the antenna working in the set range of frequencies received too low KID. From here conclusion: work at the set frequencies on distance of d=100km of does not justify.

where λ = 300/f – it is long waves of communication, m; f – communication frequency in megahertz; G0– strengthening of the reception antenna in relation to probe orientation coefficient at a working frequency; RA, XA – active and jet components of entrance resistance of the reception antenna at a working frequency in ohms (usually entrance resistance of the receiver is necessary purely active and equal 75 Ohms).

Conclusion: Proceeding from the data obtained during calculation of the first point it is possible to come to such conclusion that communication on three chosen ORCh: f=7,2 MHz, f=7,5 MHz and f=7,8 MHz satisfies Kid=0,85 since at these frequencies the expected value of probability of communication with reliability is not worse set respectively is equal: F1 (ζ) = 0,8508, F2 (ζ) = 0,9032 and F3 (ζ) = 0,9332