MEASURE YOUR AERIAL

Radio Record, Volume I, Issue 42, 4 May 1928, Page 15

MEASURE YOUR AERIAL

It is very often desirable to know what the natural electrical length of al aerial is. ‘lhe only way to measure the length accurately is by means of a wive meter-and this is beyond most people, who are interested in radio. Jut there is a way to find approximately the electrical length, and this is good enough for most people. The rule for single wire aerials: ‘Take ~ combined lenmth of aerial and Jeodin from end of wire to set, divide by three, and multiply by 4.8, or, for an inverted L-type using four wires. multiply by 4.5. This gives the approximate electrical length in metres. For example :- A single wire aerial is 100 feet long, has a lead-in wire 50 feet long. What is its electrical length 100 plus 5Q-equals 150, which is the total length in feet. 150 divided by 23-equals 50, total actual liveal length in metres. 50 multiplied by 4.8-equals 240, which is the electrical length of the aerial in metres, or, the wave-length the aerial wil] receive without additional adjustment or tuning, ‘This aerial will not receive below 240 metres with the ardinary hreadeast receiving set, although the serial will serve quite well for ultra-short-wrve reception with a short-wave receiving set.