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Electrically small antennas for 433 MHz

Electrically small antennas for 433 MHz

Electrically small antennas for 433 MHz

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!

RE: Electrically small antennas for 433 MHz

is it transmit or receive?
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

I've done something like this before.The antenna is about 30mm in height with a reasonable gain.  The idea is to attach a simple matching network to the antenna, that's all.

RE: Electrically small antennas for 433 MHz

Hi jbartos, I've built a helix before simliar to one in your article, but the gain is only -20dBi. Care to give your comments?

RE: Electrically small antennas for 433 MHz

Suggestion: Have you try another ones for higher gain? See the link for:
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 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.
 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

I'm also making a handheld 433 MHz product and want to use a coil antenna on the receiver. I've seen 2 configurations and want to know if somebody can advise me on what difference in performance to expect. The antenna sticks out from the product.

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

lockheed Martin in palmdale california has been doing alot of research in electrically small antenas. contact  Peter Von Burke @ 661-572-2359 or email him @ peter.r.von.burke@lmco.com

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