Crystal Radio With Three Sliders

Here's a new one that was suggested by Dave Schmarder. I can still hear him saying "now here is one simple enough for you to make ... it's not complicated AND it's a treasured CRYSTAL design".

And I believed the part about being easy for me to build. One must understand that I live in Oklahoma and big city folks from the State of New York tend to enjoy toying with Okies ... sort of like freckled faced kids ripping wings off flies! He is a master of radio engineering though so I jumped right at this one.

I cannot seem to do anything 'simple' and Dave seems to know this. He starts his presentation talking about a 2-slider radio but lets it slip that 3-sliders are really the cat's meow. That turns out not to be all that accurate an expression because by the time I finished this 'simple, easy, uncomplicated' set I was screaming like a #*&^?+=# cougar!

However, I've reclaimed my composure and must admit that Dave was right about how well this thing could perform. It will never tune as sharply as one using a variable capacitor but it is amazing how well it will tune with the 3 sliders. The three sliders control the detector circuit, the antenna circuit and the tuning circuit via a 100 ph fixed capacitor to ground. Dave originally said to use a 200 ph capacitor but I screwed up designing the coil and wound up with a higher value uH than his schematic called for. So just sue me or shoot me!

The set features an unusual detector stand that I learned about from Mike Starcher. Excellent control is acheived with spring-loaded leather pressure cushion pushing against the cat's whisker shaft which can be adjusted with the set-screw in the top of the pillar. The cats whisker is actually a ribbon of brass wound into a spring that is cut to an arrow point for select contact anywhere on the crystal. The point is rotated up and down or back and forth with the shaft action and the pillar rotates from side to side for 100% coverage. That brass bullet-nose sticking up to the left of the crystal is for diode reception in case you're too lazy to operate the crystal mode.

Slider operation is smooth too. The square brass slider columns have telescoping square brass sleaves riding on them with Padauck wood knobs for control. The coil form is 3" diameter pvc painted and finished with lacquer. The base and top plate are Padauck too and all if was finished with flat lacquer.

So there you have a very easy to make, uncomplicated set that can be built in a about 36 hours of hard charging. Nothing to it! And that's why the price is only (see pricelist). What a deal for minimum wage labor!
Available Order: #X-50