CIRCUIT DESIGN, INC
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CDP-02N UHF Synthesized Radio Data Module Operation Guide
9
In most cases the following basic rules will help you.
• Connect an antenna with 50 Ohm impedance for 433 MHz (458MHz).
• The easiest construction is a wire of approximately 17cm.
• Place the antenna vertically, straight up or down from the transmitter and receiver module.
• Do not cover the antenna with metal parts.
• The connection of the metal surface of the transmitter and receiver case to a larger metal
part (ground plane) will increase radiation and reception efficiency. Such metal part
should not be placed near the antenna.
• The best range is achieved if the transmitter and receiver antenna have a direct visual
connection. Any object in between the transmitter and receiver antenna, and metallic
objects in particular, will decrease the range.
• The transmission is influenced by reflections of the transmitter signal on metallic surfaces.
By overlaying the direct and reflected signal with a 180 degree phase shift the signal can
almost fade out. Such reflections and fade-outs can result in data drop-outs in mobile
applications.
• The human body can have similar effects to metal objects. Pocket transmitters should be
taken in the hand and put in a position away from the body and pointed in the direction of
the receiver.
Start-up:
After Vcc is connected to the transmitter the VCO and PLL will start-up and, after about 80ms
(EU type) or 90ms (UK type), the output frequency and power will reach the normal value.
The same start-up time is needed by the receiver after it is switched on.
Data transmission is not possible, or the data will be distorted, during this start-up period.
Therefore the input signal should be fed to the transmitter 80ms (EU type) after TX power ON.
The transmitter is active as long as the power supply is on. The power should be switched off
immediately after the data transmission is finished in order to save valuable battery power and
avoid unnecessary use of the RF spectrum.
The receiver does not use the RF spectrum actively and it can remain ON as long as desired.
Important Note:
If the modules will be installed to a control PCB (motherboard), This PCB
must be designed as a RF PCB. The surface of the PCB must be shield as much as possible.
The modules should be kept away from the MC, EPROM and crystals. In addition all the pins
of the modules should be connected via LC filters.
