The whole system was built in a package that was about 70mm x 96mm x 30mm which contained the TNC, transmitter, interface circuitry and a lithium battery sufficient for about 20hours of continuos operation. All in weight (including battery and antenna) was 135g. TNC’s are used by radio hams for data communication over narrow band FM audio channel. The TNC provides a radio modem capability – converting the data coming from the host computer interface into a format suitable for transmission over a radio channel. It takes data packets presented at the serial interface into the synchronous format used for transmission. Data is sent using a 1200 baud modem chip – which provides the signal shaping necessary to pass the data efficiently over the radio channel.
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The UK radio-licensing regime is such that only a few legal ways to transmit data from a balloon to the ground currently exist. Unlike the US the UK Ham Radio licence specifically excludes airborne operation and many of the licence exempt frequencies are barred form airborne use. Narrow-band 10mW licence exempt modules in the 434.04 – 434.79 MHz frequency range seem about the only viable option for High Altitude ballooning at present The transmitter module used was the Radiometrix NTX-2. This conforms to the licence exempt transmitter specifications and outputs a power of 10mW. The NTX-2 was selected because of its linear input to frequency characteristics (in contrast to similar modules which are more digital in operation). This characteristic allowed the module to be used with the AFSK (Audio Frequency Shift Keying) output from the TNC. Antenna The antenna used is a coax dipole – this is a very simple antenna where the outer braiding of the feeding co-ax is stripped away to expose a quarter wave of inner conductor at its end. This type of antenna was selected due to its radiation pattern – when mounted above the payload the antenna has a maximum signal strength directed at 45 degrees below horizontal – which is close to ideal given the expected range of the modules. Interface Circuit A LM324 quad op-amp was used to interface the TNC-X to the NTX-2. One of the four op amps are used to amplify the...
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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