Probabilities of interference with mobile field radio derived from a field-strength survey at 59Mc/s

The paper gives an account of an experimental investigation of common- and immediately-adjacent-channel interference areas for mobile radio networks, based on a field-strength survey at 59Mc/s over flat and hilly country in north-west Germany. The variation of field strength with distance is shown to be in close accord with calculation. Particular attention has been paid to investigating the distribution of field strength at each distance, which is shown to approximate closely to log-normal. It is also established that the variance of these log-normal distributions may be considered to have a single value for each type of country, irrespective of range. Protection ratios acceptable for satisfactory operation are determined from experimental observation of common- and adjacent-channel interference. The derived data are used to determine probabilities of interference and are presented graphically for practical use.