Tube Radio - The Moscow Square

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Growing up in West Texas I was often referred to as a square. Somehow that moniker didn't offend me since I knew from early efforts at building stuff like pigeon lofts, hawk houses and the like that making something square was, in fact, damned hard to do. Being able to do so was, to me then, kind of a crown of achievement.

So when it came time to build a square version of the old Moscow design I flew into the prospect with great fervor (that means 'with great heat' as my 13 year old son just told me) All that schooling he's getting is paying off already! Besides, those giant triangular variable caps have become impossible to find and I'm finding that the square result is much more pleasing to look at even those caps are getting rather difficult to find as well.

Dave Schmarder taught me how to handle the very large 800pF value of this monster square variable capacitor by placing fixed capacitors in series in the circuit going to the grid leak. The radio also employs a 1000pF electrolytic capacitor between the stepped down voltage and ground to help control noise on his advice. Dave also recommended using a 27mH choke collared by two 500pf capacitors to ground to remove remaining radio signals prior to the headphones. All of these instructions have proven to be well worth the humongous consulting fee that was extorted.

The set operates with a VT136 tube and a 12 vdc wall wart for power which eliminates the need for multiple voltages, pesky batteries and dangerous voltages and currents. Even a child can play with it until, of course, curious hands turn to destructive hands and feet!

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I live 65 miles from the nearest transmitter and yet I receive 11 stations using a 55' antenna that is only 9 feet off the ground. Initially I had strung a very long antenna 330' long 19 feet off the ground but my radios had unbelievable static and noise - 1000pF capacitor or not. I had the antenna exorcised by a leading exorcist but to no avail. Then my brilliant kid suggested that perhaps those high power lines strung 2 feet above the antenna wire might be the problem. Did I detect insolence? His doctors say he should mend quite nicely!

Both the main coil and the tickler coil are wound on a 4" diameter plexiglass tube that has 1/8" walls using .031" diameter wire. The main coil is measured at 243µH and the tickler comes in at 9µH which creates just the right amount of regeneration controlled by a 5kohm pot. A very special knob for regeneration control was machined of solid brass to match the plate cap and has provided a certain continuity for the set.

The Moscow Square also sports a 2" thick slab of Padauk wood as a base rather than the standard 3/4". It is very costly but the resulting appearance is more than worth the outlay. I also developed a new process of projecting the tube up away from the upper plate with brass stilt-like tubes that create a very striking majesty that all commissars tend to revere. Even the Moscow style onion cap was machined with additional height that compliments the spiring qualities favored in the Red Square. (I may be 'square' but I'm definitely NOT red so any of you neo-McCarthy types can just forget it!)

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