AM RF T
RANSMITTER
M
ODULE
.
Operation
AM-TX1-XXX
The application circuit shows how to drive the module. The module may be driven from either a current
source or current sink. In both cases the dropper resistor is required to set the drive current. The maximum
and minimum drive voltage for various dropper resistor values is shown below. For other voltages between 2.5
- 13.1V the values may be calculated using the following formula
Min Rd = ( Max drive Voltage - 3 ) / 0.0046
The minimum drive voltage for a given resistor value may then be calculated as;
Min drive Voltage = 2.2 + .003 * Rd
Example:
The max drive voltage is 5.5V. The min Rd is therefore 543
Ω.
The nearest preferred value above
this is 560
Ω.
The min drive voltage with 560
Ω
is 3.86V.
ANTENNAS
Two types of antenna may be used, a tuned loop, or a short whip. The tuned loop should be driven directly
from the module. The whip should be driven via the specified tuning network. The module is not type approved
for use with a
1
/
4
wave or helical type antenna.
Tuned Loop Antenna
Short Whip Antenna
90mm MAX
~
~
RF Ground
Max
700mm2
1-5pF
RF Ground
1
-5pF
The tuned loop Ant is constructed from wire
of 1-1.5mm DIA, or PCB track of 1.5-2.5mm
width.
The enclosed area of the loop shall not
exceed 700mm2. The trimming capacitor
should be used to tune the ant for max
output. A 1.5 - 5pF cap is generally
adequate.
The short whip ant is constructed from a
wire rod or PCB track of 90mm length.
The 15nH inductor may be an SOIC
component on the PCB, or an air cored
solenoid of 0.8mm inside DIA, close wound
with 9 turns of 0.56mm. The trimming
capacitor should be used to tune the ant for
max output. A 1.5 - 5pF cap is generally
adequate.
MECHANICAL DETAILS
Width = 7mm, Height = 11.5mm, thickness: 4.5mm.
+ve connection is shown by marking on body side
Lead Pitch 5.08mm.
11.5mm
+ve Side
7.5mm
5.08mm
4.5mm
DS012_1
Oct 00
©2000
REG No 277 4001, ENGLAND.
Page 2
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