1961 symposium digest — sixth part of the digest — second half

The level of electromagnetic interference from electrical overhead transmission lines was investigated by The Hinchman Corporation under Contract NO-y88454 and NBy-17792. These investigations established the level of interference which could be expected from well-maintained overhead electrical transmission lines of the 69KV and 120 KV class over the frequency range of 15 kilocycles to 1,000 megacycles, using Stoddart Aircraft Radio Company, Inc., Radio Interference and Field Intensity Measuring Equipment. Results of these investigations indicated that interference in terms of the quasi-peak function decreased inversely with frequency from 15 kilocycles to approximately 15–20 megacycles. Beyond the 20 megacycle range, there appeared a leveling-off of the curve and eventually a rise in this curve from 40 megacycles to 1,000 megacycles. The field measurement tests indicated that all data obtained about 20 megacycles was due to the internal noise of the receivers. This fact was verified under field conditions by removing the antenna from the set and noting the meter needle indication.