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By the early thirties, National had grown from a company that produced radio parts and regenerative TRF receivers into one of the top shortwave receiver producers in the country.
National's chief engineer and general manager, James Millen, had guided the company from its early radio designs (that usually had National as a parts supplier) into the new shortwave receiver market that was becoming popular by 1930.
In addition to the RHM and AGS receivers, National also produced the RHP and RHQ receivers that were very similar to the RHM within the circuitry but ganged the three coils together behind a small panel that created a plug-in "coil set" for each tuning range covered.
Frequency coverage of the RHM is 2.3mc up to 15.0mc using a set of 15 coils.In late-1931, National Company was selected by the Department of Commerce (who was in charge of airports and airways through the Aeronautical Branch) to build new superheterodyne receivers to replace the old regenerative receivers then being used at airports around the country.The entire system upgrade of airport communications equipment included General Electric, who got the contract for the new transmitters and Aircraft Radio Corporation, who got the contract for the new airborne gear.The AVR-11 receivers provided frequency coverage from 140kc up to 23mc which was more or less standard for the largest "All-wave" receivers.The airports favored the longer wavelengths used in air navigation, weather reports and for some airport communications in the 1930s.