RCT-433-AS Radiotronix, RCT-433-AS Datasheet - Page 7

• Manufacturer Part Number: RCT-433-AS
• Description: RF Modules & Development Tools 433MHz Transmittter Module 2400 Baud
• Manufacturer: Radiotronix

Specifications of RCT-433-AS

• Supply Voltage (min): - 0.3 V
• Product: RF Modules
• Maximum Frequency: 433.92 MHz
• Supply Voltage (max): + 15 V
• Supply Current: 4.5 mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

RCT-433-AS
Low-Cost SAW-stabilized surface mount OOK RF transmitter
© 2001,2002,2003 All Rights Reserved
Antenna Output
Pin 1 is a 50 ohm antenna output. It will support most antenna types, including printed antennas
integrated directly onto the PCB. The performance of the different antennas varies. There are
many good application notes available that describe external and PCB trace antennas. We
maintain a list in the technical support section of our website.
DESIGN HINT “Antenna traces”:
th
Any time a trace is longer than 1/8
the wavelength of the frequency it is carrying, it should be a
50 ohm micro strip. This ensures that a proper match is maintained between the transmitter
output and the antenna.
DESIGN HINT “Harmonic Filter”:
The impedance at the antenna power affects the VSWR, power output, and harmonic output of
the transmitter. In most cases, the output of the transmitter may need a low-pass LC filter to
reduce harmonic emissions. A good calculator is available on line at
http://www-
users.cs.york.ac.uk/~fisher/lcfilter/. Calculate the filter for a 3dB cut-off of the module’s center
frequency plus 10%. For example, the cut-off for a 433.92 MHz module would be about 470
MHz.
DESIGN HINT “T-Pad”:
The RCT-433-AS transmitter can be sensitive to unbalanced or unmatched loads and could fail to
operate or operate intermittently in this condition. Try to match your antenna load as close to 50
ohms as possible. Use a T-pad if necessary to give the transmitter a close 50 ohm match before
your antenna. A T-pad will also act as an attenuator. See figure 6 below, for a T-pad
match/attenuator circuit.
Figure 6: T-pad Example.
Resistor values in this T-pad example are:
R1 - 10 ohms.
R3 - 150 ohms.
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6/7/2005