Copyright © 2018 KG7TR. Technical information on this site may be shared in the interest of promoting the hobby of amateur radio. I do ask that you give proper credit to KG7TR for my equipment designs.
Closeup of VFO compartment. Transmitter and receiver VFOs are identical, and cover 5.0 to 5.5 MHz. They are very stable.
Octalmania transmitter stacks on top of receiver and picks up receiver's VFO signal from below for transceive.
Side view shows simple braces made from aluminum angle and bar stock.
Mixer coil from transmitter shows typical construction. Coil cans are from scrapped Command set receivers, with octal plug added to base for easy removal. Original air variables at top are used, one for each band.
Rear view of stacked set. Power for transmitter comes from an external Heathkit HP-23B supply.
Transmitter top and bottom views. Small cage topside shields 12SN7 carrier oscillator tube to prevent stray RF radiation. Receiver has one too.
A complete technical description of the Octalmania radio set is available at the button below:
Receiver top and bottom views. Both transmitter and receiver use INRAD #2309 9 MHz crystal filters and matching carrier crystals. Freq displays are from AADE.
Transmitter PA cage. Pair of 6883Bs (12 volt version of 6146B) puts out 100 watts PEP with ALC. PA coil is wound on old ARC-5 coil form.
Balanced modulator coil. This is a trifilar broadband coil wound on a FT-43A form. Air variables were intended to provide vernier phase balance but didn't make much difference.
Success with the Vintage SSB Special prompted me to try a SSB vacuum tube radio with conventional rack and panel construction. I also wanted to take advantage of the 80 and 20 meter coverage afforded by a 9 MHz IF and 5 MHz VFO, because there are vintage SSB radio nets on both bands. And having obtained a whole bag full of octal sockets at a hamfest, the idea of using all octal tubes hit me. The goal was to see if these tubes, most of which were designed before WW II, could still produce good SSB. Octalmania proves they do. There are 12 octal tubes in each radio. Like the Vintage SSB Special, these radios also transceive. Note the simple mechanical braces for the stacked set. These radios were described in the August 2011 issue of Electric Radio magazine. The front panels were later refinished and knobs changed to match the Octal Tri-Bander Transceiver and 2X-813 linear.
Latest schematics and parts lists are available at the buttons below: