TX2A RADIOMETRIX [Radiometrix Ltd], TX2A Datasheet - Page 8

• Manufacturer Part Number: TX2A
• Description: UHF FM Data Transmitter and Receiver Modules
• Manufacturer: RADIOMETRIX [Radiometrix Ltd]

Antenna requirements
Three types of integral antenna are recommended and approved for use with the module:
Fig.6: Antenna configuration
A) Helical
B) Loop
C) Whip
The antenna choice and position directly controls the system range. Keep it clear of other metal in the system,
particularly the 'hot' end. The best position by far, is sticking out the top of the product. This is often not
desirable for practical/ergonomic reasons thus a compromise may need to be reached. If an internal antenna
must be used try to keep it away from other metal components, particularly large ones like transformers,
batteries and PCB tracks/earth plane. The space around the antenna is as important as the antenna itself
Radiometrix Ltd, TX2A/RX2G Data Sheet
Antenna selection chart
Features
Ultimate performance
Easy of design set-up
Size
Immunity proximity effects
Range open ground to similar antenna
(for TX2A-433-14-5V & RX2G-433-15-5V)
B. Loop antenna
C. Whip antenna
A. Helical antenna
Wire coil, connected directly to pin 2, open circuit at other end. This
efficient given it's small size (20mm x 4mm dia.). The helical is a high Q antenna, trim the wire
length or expand the coil for optimum results. The helical de-tunes badly with proximity to other
conductive objects.
A loop of PCB track tuned by a fixed or variable capacitor to ground at the 'hot' end and fed
from pin 2 at a point 20% from the ground end. Loops have high immunity to proximity de-
tuning.
This is a wire, rod, PCB track or combination connected directly to pin 2 of the module.
Optimum total length is 15.5cm (1/4 wave @ 433MHz). Keep the open circuit (hot) end well
away from metal components to prevent serious de-tuning. Whips are ground plane sensitive
and will benefit from internal 1/4 wave earthed radial(s) if the product is small and plastic cased
16.4cm
C3
C4
C2
RF
RF
C1
RF-GND
RF
0.5 mm enameled copper wire
close wound on 3.2 mm diameter former
433 MHz = 24 turns
wire, rod, PCB-track or a combination
of these three
433 MHz = 16.4 cm total from RF pin.
Feed point 15% to 25% of total loop length
track width = 1mm
4 to 10 cm inside area
helical
**
**
***
**
200m
A
2
100m
*
*
**
***
loop
B
300m
***
***
*
*
whip
C
antenna
is
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