Used Zener Diodes to derive the stabilized voltage for the Hartley oscillator (although I did find a couple of suitable voltage stabiliser valves (CV287) whilst sorting through a box of valves this morning). Whilst sniffing around in that box of valves mentioned above, I was adding to my catalogue of valves `in stock`, in which I like to include links to a data sheet. Whilst doing that,
Click here to download the full size of the above Circuit.
I noticed something I had never realized before. The ECC81 used in the local oscillator is also widely know by the equivalent name 12AT7 (as mentioned in describing the BFO). What I never twigged before is the obvious fact that the valve should use a 12V heater supply (obvious because I knew all this from the 6SK7s etc used in my Paraset - I was considering replacement with 12SK7s to make battery operation easier). Accordingly, I had wired up the heaters for the two 12AT7s in this project for only 1/2 the rated heater voltage - amazing that they still worked at all (and another possible explanation for the fun and games I had with the BFO, as described here. ) Note to self (and any others who happen to be reading): this is also true for the double triodes ECC83 / 12AX7 and ECC82 / 12AU7, widely used in audio frequency gear. . you can see the coil at bottom left. You can also see that I only have a single gang capacitor - which is going to be a problem (I need a twin-gang device; one for tuning the LO and one for tuning the resonant circuit at the input). That will have to be dealt with in the future - for now the carol service from from King`s has just kicked off.
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.....
characters left: