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FMT-2705 (Obsolete)
1/2 Watt 27MHz Radio Data Module
Features
• Enables sending of digital data up to 2000m
• Digital Data supported: pulse width modulation signals, singals from standard encoder-decoder circuits of the given bandwidth
• Direct FM modulation
Application
• telecommand
• radio data communications
• commercial / industrial telemetry.
This product is now Obsolete and is replaced by FMT-2712 |
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Description
The data module allows you to send your digital data up to 2000 metres, when used with the Elsema FMR-05D receiver. Digital data such as pulse width modulation signals and signals from standard encoder-decoder circuits of the given bandwidth, can be transmitted by direct FM modulation.
Applications include telecommand, radio data communications and commercial/industrial telemetry.
Compatibility
All Elsema type FMR-… series:
FMR-05
FMR-05D
Technical Data
Supply Voltage |
4.5 - 5.5V. Absolute Maximum 7VDC |
Supply Current |
420mA when enabled pin to +5V
less than 1uA disabled and "M" terminal to 5V |
Enable Voltage / Current |
5-13.5VDC, max current 50uA |
Operating Frequency |
27.145MHz (Other freq. available: 27.045, 27.195 & 27.455MHz. NB. 27.455 freq. is not available for Australia ) |
Oscillation System |
Crystal Controlled, 30ppm at 0-50 deg C |
Operating Temperature Range |
0-50 deg C |
Data Input Level |
Data should swing close to ground and +5V |
Frequency Response |
100Hz to 2400Hz |
Baud rate |
300-2400bps. For a baud rate of 4800bps a 2.2kOhms resister should be used in series with terminal "M". Manchester code is recommended |
Recommended Receiver |
FMR-05D (Outputs your digital data) |
RF Power Output |
1/2W into 50 ohms. |
Antenna |
ANT27L with 50 ohms, shielded cable |
Type of Emission |
Narrow-band-width Frequency Modulation (5K00F1D) |
Frequency Deviation |
1500Hz non-return to zero |
Harmonics |
Less than -13dBm (50uW) |
Weight |
8 grams |
Useable Operating Range |
Up to 2000m line of sight |
Block Diagram
| + |
5V DC Positive Supply |
| E |
Enable pin. When +5V applied to this pin the transmitter is enabled. 0V disables transmitter |
| M |
Data input (FM-modulation input). Data should swing close to ground & +5V. A data rate of 2400 baud can be transmitted. For a baud rate of 4800 a 2.2k Ohms resistor should be used in series with terminal M. |
| - |
Negative to supply, ground & RF-ground |
Data Format
It is important to input the correct data format otherwise the receiver will have a lower sensitivity which will result in a reduced transmission range.
The FMT-2705 data should be set for 50/50 duty cycle, therefore the "data in" should have a 50/50 duty cycle. The 50/50 duty cycle data can be pulse-width modulated to transmit resets, 0's or 1's. See diagram below:
A 50/50-duty cycle will have an average DC signal resulting in a constant reference for the data slicer. Users should use pulse-width modulation to transmit data with logic 1's or 0's.
If a different duty cycle is used, for example 66/33 ( Manchester format) the data slicer in the receiver will try to adjust itself to the average DC signal. Since this average DC signal is changing with different data bits this will result in a constantly changing reference for the data slicer, resulting in lower sensitivity. See diagram below :
Only 50/50 duty cycle data is suitable for the FMT-2705 transmitter and FMR-05D receiver.
Dimension
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