You see, I discovered this while wiring up my first spider-web crystal set in the basement. An aside, I thought this spider web would provide company for the real ones here and there in the corners. My spider coil is shown in the picture at right. It consists of 55 turns of #22 AWG enamel wire wound on an 1/8th inch thick 5 by 6 inch piece of ABS plastic. The inner diameter of the coil is about 1.5 inches and the outside diameter is about 4.5. Total inductance turns out to be about 250 uH, perfect for an AM band crystal set.

spideer web coil

My AM band antenna runs 20 feet up to the eve and then another 20 feet into the attic, east-to-west. The antenna feed attaches to the single tap I provided on the coil, about midway. Next time I’ll add more taps to the coil to aid in tuning the antenna a bit better across the AM band. The full coil is paralleled with an air variable 365 uuf cap and  attaches to the anode of a 1N34 germanium diode. The ear piece attaches to the diode cathode and in parallel with the 47K detector resistor to ground. That’s the rig! Compared with a cylindrical coil, this set is hotter; I could hear five stations immediately, including Topeka (W1BW, 580), KC SPORTS (810) and of course the local, KLWM at 1320 on the dial.

coherer CW

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