T7 / R7
T7G / R7G
FM 433MHz Narrow Band
Application Circuit
The application circuits show how the FM narrow
band transmitter and receiver modules can easily
be integrated into a system to form a wireless link.
Application Information
Antenna Design
The design and positioning of the antenna is as
crucial as the module performance itself in
achieving a good wireless system range. The
following will assist the designer in maximising
system performance.
ANTENNA
+5V
+5V
The antenna should be kept as far away from
sources of electrical interference as physically
possible. If necessary, additional power line
decoupling capacitors should be placed close to
the module.
1
2
3
4
5
6
7
8
9
18
17
16
15
14
13
12
11
10
A0
A1
A2
A3
A4
A5
A6
A7
VSS
VDD
VT
1K5
Ω
R7 / GR7
1
2
3
4
5
6
7
ROSC
OSC1
OSC2
DIN
The antenna ‘hot end’ should be kept clear of any
objects, especially any metal as this can severely
restrict the efficiency of the antenna to receive
power. Any earth planes restricting the radiation
path to the antenna will also have the same effect.
D11
D10
D9
DATA OUT 4
DATA OUT 3
DATA OUT 2
DATA OUT 1
D8
HT12D
ANTENNA
+5V
Best range is achieved with either a straight piece
of wire, rod or PCB track @ ¼ wavelength
(15.5cm @ 433.92MHz). Further range may be
achieved if the ¼ wave antenna is placed
perpendicular in the middle of a solid earth plane
measuring at least 16cm radius. In this case, the
antenna should be connected to the module via
some 50 ohm characteristic impedance coax
+5V
T7 / GT7
1
2
3
4
5
1
2
3
4
5
6
7
8
9
18
VDD
A0
A1
A2
A3
A4
A5
A6
A7
VSS
17
16
15
14
13
12
11
10
DOUT
OSC1
OSC2
TE\
ROSC
AD11
AD10
AD9
AD8
Helical Antenna
HT12E
RF
34mm @ 433MHz
17 turns equally spaced
Figure 5: FM Narrow Band Transmitter &
Receiver Application Circuits
∅
= 5mm (inside)
Whip Antenna
RF
15.5cm @ 433MHz
Figure 4: Antenna Configurations To Be Used
With The FM Narrow Band Transmitter &
Receiver Modules
DS307-7 Oct 05
©2004 REG No 277 4001, England.
Page 6
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