Building a foxhole radio is rewarding and the basic setup is very simple. It is, however, difficult to adjust, and it may take several attempts to find a proper razor blade for the detector. This is a project that requires patience and much trial and error, but it will pay off once it begins to work. It will help to be versed in the construction and operation of crystal sets before building one. It will be especially helpful to read the introductory notes about the coil, detector, antenna, and other components. These sets are extremely simple in construction, but tuning and modification require some basic understanding of theory, as well as practice.
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All sets presented here are based on old articles, notes, and people's recollections. There are fairly major variations in design and materials among these plans. It must be remembered that these were improvised under often adverse conditions; there was no "standard" design. With this in mind, take this entire article as a whole, and use it a bit here, a bit there, to build towards a design that works best using modern materials. Refer to the schematic for wiring and connections. Wind the coil 100 turns around the tube. #22 AWG wire is recommended, but it is likely that whoever was in the field used whatever gauge was in the scrap coil, motor, or transformer they were cannibalizing. Spray / paint the coil with lacquer (or whatever is handy) to set it firmly. Scrape off whatever paint or varnish may be on the wire used for the tuner/slider. Spread the safety pin apart and bend the head 90 degrees to use it as a base for attaching the pin to the base. The pin should stick up from its bent head, then down to its point where the pencil lead is attached with some of the wire left from winding the coil. The sharpened pencil lead is the detector, which touches the razor blade, which is in turn attached to the base at one of its ends (through the hole) with a screw or tack. The tuner should be mounted so that it is free to pivot and slide across the coil (see the crystal radio page for basic construction tips). Use a scrap of paper...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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