NBS Circular 120: Construction and Operation of a Simple Homemade Radio Receiving Outfit
Alternative Name: Crystal Radio Receiving Set
Frequency: 500 to 1,500 kilohertz (200 to 600 meters wavelength). In the USA today’s AM broadcast band extends from 540 to 1,700 kilohertz. Unless changes are made to the tuned circuit, 1,500 to 1,700 kHz will not be heard.
Antenna Requirement: 23-meter (75-foot) long or more outdoor wire antenna. With an added two or three-transistor amplifier, most crystal sets can operate with a 5-meter (17-foot) long or less indoor wire antenna. Alternatively, a 1-meter by 1-meter (40-inch by 40-inch) loop-type crystal radio receiver may be preferred.
In addition to the parts listed, modern construction requires an impedance-matching transformer between the receiver and today’s 32-ohm-impedance headphones or earbuds – Xicon 42TM013 or equivalent.
Crystal-set builders learn the minimum requirements for receiving radio communications and the function each part performs. Builders may also enjoy keeping a log of stations received – their call letters, frequency and date and time received.
NBS Circular 120 recommends obtaining Principles Underlying Radio Communications – Signal Corps Pamphlet #40 for a deeper radio principles understanding. See
Of course NBS Circular 120 may be read for the historical insights it contains.