This article presents a description of a 70cm wideband transceiver for duplex operation. The modules are designed for operation in a 200 kHz wide duplex channel, freely selectable from 430-440 MHz with a 100 kHz channel spacing. First prototypes were introduced on the international Packet Radio Symposium in April 1997. Some minor changes resulting
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from further experience were added to the text since then. Narrow-band packet radio net access frequencies with 25kHz channel spacing for operation with either 1k2 Baud AFSK or 9k6 Baud FSK are state-of-the-art and standard for over 15 years now. They are common in wide areas of Europe. These transmission speeds are sufficient for connecting local BBS systems, taking part in packet radio conversation groups or accessing DX clusters. There are, however, new emerging applications requiring higher transmission speeds. These requirements ask for higher speeds of one order of magnitude compared to the standard 9k6 Baud operation. Examples for such applications are new BBS systes with HTML graphical user interfaces, digital voice transmission or image transmission in real-time following the ISDN standard. Inter-node links following those requirements are currently being set up. High-speed user accesses to the packet radio network are still missing. In Germany, there is currently a single 70cm packet radio channel assigned for user accesses with a bandwidth of 200kHz. This channel has experimental status and the assignment of further channels cannot be foreseen. Therefore, the user TRX is designed as a single channel version without any user interface for changing the frequency. The frequency however, should be changeable through re-programming. The transceiver must be adaptable to be used either as part of a digipeater or a user...
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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