9/3/2020 0 Comments Pocsag Function Bits
In concept, almost any result frequency can be selectable with nearly any input frequency, but selecting a lower regularity crystal gives you even more resolution and presents less spurious noise.THE HARDWARE The present version of the BTS equipment can be a little panel with a photo 18F microcontroller with a firmware that obtain commands through an UARTRS232 port, make the POCSAG information and transmit it making use of the ADF7012 UHF transmitter.
This panel has not really be created to become used solely with OSOMCOM P0CSAG but to become used as a common low strength radio stations transmitter. Other makes use of of this plank include testing with 433MHz key boards, cargarage remotes, data hyperlinks, APRS, etc. The board has become made to become very cheap (less than 15) and easy to develop with. Board functions Central processing unit: PIC 18F14K22 16MHz Memory space: 16KN Flash 512 Bytes Ram memory 256 EEPROM Transmitting regularity: selectable from 75MHz to 1GHZ (but some components beliefs may require to become changed. Even more about this afterwards) Supported modulations: FSKGFSKOOKGOOKASK. FSK is usually utilized for POCSAG) Transmitting bitrate: seIectable up to 179.2 kbps (51212002400 for POCSAG) Transmission power: selectable up tó 14 dBm (20mW) UARTRS232 port Debuggingprogramming port for ICDPICKIT Development slot with 4 GPIOs SMA connection for antenna Strength: 3.3 volts; 50mA Size: 4.4 cm back button 4.6 cm Power supply The strength supply offers a really basic and regular design. The 5 volts input is changed to a 3.3 volts provide making use of the MCP1700T-3302 low-drop voltage regulator from Microchip. A diode protecting the insight from a reversed link could become convenient, but I didnt put it in the style. I am just assured that the consumer is not really that stupid Microcontroller The mind of the plank is definitely a Microchip Photo 18F14K22. The radio component A ADF7012 from Analog Gadgets is utilized as radio stations module. This convenient UHF low-power radio stations transmissor facilitates FSK, GFSK, 0OK, GOOK ánd ASK modulation át a optimum price of 179.2 kbps and the included Energy Amplifier can deliver up to 20 mW without making use of an external antenna driver. An inner PLL with seIectable divisor synthesize almost any desired output frequency in a variety from 75MHz to 1GHZ using just a 4MHz quartz. Modulation scheme, output power, output rate of recurrence and other transmission parameters are usually selectable through this interface. In my viewpoint, due its flexibility, flexibility and simpleness to use, this is one of the greatest sub-GHz included transmisor out there. Nevertheless, the absence of documents and examples create it a little bit annoying to work when you are starting. The datasheet will be sometime confusing and occasionally insufficient. For example, it doesnt provide a desk or chart with the output impedance of the RF output. HOW THE HELL ARE YOU GOING TO Complement THE ANTENNA lF YOU DONT Find out THE IMPEDANCE Of course you can often make use of a network analyzer and gauge it, but however I dont have accessibility to one, therefore I just do my best trying to guess the impedance at my functioning frequency using the schematics of the application examples. They are for different frequencies, but I did an interpolation and it works more or much less fine. ![]() If you require more information, refer to thé ADF7012 datasheet. To become more specific, the crystal regularity describes the result frequency quality. The output frequency is a described with the equation Fout Fcrystal (NR) OD becoming N a 812 pieces fractional number, Ur a 4 bits integer quantity and OD (Output Divider panel) will be 1,2,4 or 8. The value óf N,R and 0D are usually selectable through the SPI user interface. In concept, almost any output frequency can be selectable with nearly any insight frequency, but choosing a lower frequency crystal gives you even more resolution and presents less spurious noise.
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