|
Title: Screen Modulate Your Globe Chief: Poptronics Post by: WA4WAX on April 21, 2016, 12:17:30 AM See page 68. Tow tubes, and away you go!!
http://www.americanradiohistory.com/Archive-Poptronics/60s/61/Pop-1961-03.pdf Title: Re: Screen Modulate Your Globe Chief: Poptronics Post by: W2JBL on April 24, 2016, 07:21:22 PM I had a Globe Cheap a while back and built a modulator on the chassis using a 6L6, and found the rig worked very well screen modulated. Timtron has it now I think. Anyway the grounded grid 12AT7 input stage shown is useful for more than a carbon mic. I used it for the first stage in the modulator I built for my most recent ARC-5 setup, but modified. I put a 1K resistor from the cathode of the first stage to ground, and a 47MF coupling cap from the cathode end to the mic input. It makes a wonderful high level (-10 to 0 DBM) input impervious to RF. For the carbon mic bias I used the output of a 7808 regulator IC through a 680 ohm resistor to the carbon (or amplified dynamic in my case) mic. The IC is powered by rectified filament voltage or DC filament voltage from the car's battery source. A toggle switch disables the mic bias for line audio. If I jam a T-17 carbon mic into it it's instant "bandits at twelve o'clock" audio. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
|