The Story of the 75A-5 Receiver

This home-made SSB receiver was designed and built by Bill Simons, W9BB, (then W9YXJ) in 1956. It was named the 75A-5 (one step up from the Collins 75A-4).

The basic receiver (bottom unit) tunes 3.5-4.5 MHz, and is double conversion. It has a 3-stage AGC and a "Q-multiplier."

The VFO is a PTO which was used in the Central Electronics 100V transmitter. It tunes 1 MHz and is linear. Each division on the round dial represents 1 kHz.

The filter is a 3.1 kHz Collins mechanical filter. This filter was hand selected by Collins and has very sharp skirts. The product detector is a type 7360 beam deflection tube. Both of the mixers are triodes for low noise.

The upper unit is a crystal controlled converter which converts each of the ham bands to the 3.5 to 4.5 MHz range. The mixer is a nuvister tube for low noise.

This receiver combined with a homemade crystal filter SSB transmitter (output 150-watts) were used by W9BB in 1957 - 1960 to work over 125 countries on SSB.

The receiver was evaluated by the late Marv Eichorst, W9RUK, and found it to be superior to his Collins 75A-4 and Hallicrafters SX-115.

I have to brag about something.

Bill Simons, W9BB