For the long-distance listener (dx-er) it is a treat to listen on a band 8MHz wide which normally is completely empty, but which is capable of providing periods of clear reception during the `Sporadic E` season from several distant countries. Usually only one or two transmitters will occupy the band for a few tens of minutes, but when the ionisation
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is widespread and intense the band can become jam-packed with pop stations, speech, news and cultural programmes for many hours It is interesting to note that, although the modulation details are the same as in the western CCIR FM band, occupying the same 200 - 250kHz of spectrum, the channel spacing is now 30kHz, rather than 100kHz. This is comparable to the `offsets` as used in TV channels to avoid co-channel interference. The pre-empahsis is 50kHz as in western Europe, and Zenith multiplex stereo is increasingly used, as well as the Soviet system in which the difference signal is transmitted as an AM reduced-subcarrier signal at 31. 25kHz. Tuners made for the band occasionally turn up on ebay. de, and there must be heaps of abandoned tuners in, say, Poland and Hungary. Locally produced PLL models were made by Diora in Poland and Teleton in Hungary. Several PLL synthesised models have been produced by Japanese manufacturers including Sony and Technics and generally offer manual switching between the two stereo systems. However, the `DX` community tends to use high-end `scanning` receivers or general-coverage VHF receivers, such as the Icom PCR-1000 or R7100 for this band. Alternatively, a dedicated receiver for the band can be made cheaply by modifying an old Band II FM tuner. The ideal model to choose would have both an FM `Tuning Meter` and Signal Level Meter, but the choice of tuner requires internal inspection of...
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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