National Radio Institute (NRI) AM radio kit

  
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This National Radio Institute radio kit covers the AM broadcast band from 550 to 1700 KHz. The set was designed to be constructed as part of a radio course taught through NRI. In contrast with some other correspondence course kits such as a later NRI chassis, it uses a safe transformer power supply. Tubes are a 6BA6 RF amp, 6BE6 converter, 6BA6 IF amp, 12AU7 detector and first audio, 6AQ5
National Radio Institute (NRI) AM radio kit - schematic

audio out and 5Y3 rectifier. NRI was well-known as a correspondence school for electronic technician training. NRI also produced a line of kits such as test equipment and a simple Novice ham radio transmitter/ receiver under the NRI and Conar labels. I first thought the cabinet was an excellent home-brew job. After removing the chassis, I noticed a rubber stamp on the inside bottom of the cabinet. This was indeed an NRI-supplied cabinet which I am told was available at extra cost. The chassis has IF transformers of two different sizes, several large over-sized resistors, a 12AU7 (dual triode) in place of the usual 6AV6 for detector and audio preamp, a choke in the power supply as a partial PI filter, a negative power source for audio output tube bias, three 1000 ohm resistors in parallel to develop that bias, and some other unusual features. I was wondering if someone had substituted components or simply miswired a couple of items such as the power choke. It turns out that ALL of the unusual features were designed into the set. I obtained a paper copy from George K. of the 68 page NRI lesson set 7E1 for this radio titled "Practical Demonstrations of Radio-TV Fundamentals; Instructions for Experiments 61 to 70". The unusual parts were either recycled from previous experiments or were included for a series of tests conducted in the process of building the radio. The tests and experiments include a simulated series of induced...



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