Electrically small antennas for 433 MHz
Electrically small antennas for 433 MHz
(OP)
Could anyone give me a hint on electrically small antennas for 433 MHz? The antenna shouldn't be larger than about 30mm in diameter and it will be placed close to a ground plane (1mm). I know that the antenna performance will be extremely poor but maybe some solutions are better than the others. Loading will be needed in order to get some bandwidth.
Thanks in advance!
Thanks in advance!





RE: Electrically small antennas for 433 MHz
with receive only possibly the best way would be to use the antenna as a voltage field probe and convert from high impedance to low impedance with an amplifier and balun
if it is t/r then this would work on the receive side with another matching network for the transmitting side
RE: Electrically small antennas for 433 MHz
RE: Electrically small antennas for 433 MHz
http://www.awirelessworld.ch/data/radio/bim2.pdf
etc. for more info
RE: Electrically small antennas for 433 MHz
RE: Electrically small antennas for 433 MHz
Antenna requirements
Three types of integral antenna are recommended and approved for use with the module:
A) Helical Wire coil, connected directly to pin 2, open circuit at other end. This antenna is very
efficient given its 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.
B) Loop 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.
C) Whip This is a wire, rod ,PCB track or combination connected directly to pin 2 of the module.
Optimum total length is 16cm (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
A B C
helical loop whip
Ultimate performance ** * ***
Easy of design set-up ** * ***
Size *** ** *
Immunity proximity effects ** *** *
Range open ground to similar antenna 200m
RE: Electrically small antennas for 433 MHz
Config. 1: 0.5mm wire, 20mm long X 4.2mm diameter, 24 turns.
Config. 2: 1mm wire, 30mm long X 7mm diameter, 17 turns.
RE: Electrically small antennas for 433 MHz
http://www.radiometrix.co.uk/dsheets/bim2.pdf
and search for helical antenna
http://www.geocities.com/euro446/tech.html
etc. for more info
RE: Electrically small antennas for 433 MHz