Helical coating wire antennasAdvanced Radio Telemetry

Datasheet

Helical antenna is a wire coil basically - one of the terminations is directly connected to the antenna input/output pin of RF module or radio modem. This antenna type is very efficient given its small size.

As well as all the unipole antennas, the helical antenna has enhanced sensitive to any conductive and non-conductive objects in close surroundings. So please be aware of this fact that antenna surroundings is a integral part of this type of antennas and have a fundamental influence to the final antenna parameters as impedance, SWR, etc.

To reach a correct antenna features it is necessary to ensure a regular ground plane. Its shape and dimensions have an influence to the final antenna features as well. Generally, the area radius should be /4 at least. It is not easy to provide it in many cases.

Also any ground plane parallel placed with the antenna axis makes undesirable capacities that sadden the antenna parameters. So it is recommended to trim the wire length number of turns - for optimum results. In this case you reach an excellent, small and cheap antenna for your application.

868 MHz Helical antenna:

433 MHz Helical antenna:

7 and turns; made from spring steel with Ag coating Helical dimensions:Diameter: appr. 7.2 mmHeight (under soldering pin): 27 mmGround plane: Tin plate; appr. 52 mm diameter Features:Frequency range: 849 885 MHzVSWR: < 1.5Impedance: 51 + j 2 Ohm

15 and turns; made from spring steel with Ag coating Helical dimensions:Diameter: appr. 8 mmHeight (under soldering pin): appr. 34 mmGround plane: Tin plate; appr. 70 mm diameter Features:Frequency range: 428 438 MHzVSWR: < 1.5Impedance: 47 + j 3 Ohm

PCB, e.g.

Ground plane area

Variants and ordering information:868 MHz Helical antenna:Part Number: ANT868HEL nn xxx yy

433 MHz Helical antenna:Part Number: ANT433HEL nn xxx yy

Where:nn number of turns

(standard: 7.5 turns for 868 MHz; 15.5 turns for 433 MHz)xxx antenna polarization - see images below

VER - bend on the soldering pin - standardHOR no bend on the soldering pin as option

yy coating typeAg Silver plated (excellent)Sn Tin platedCu Copper (economical)

Made from:Spring steel (EN 10270:1 DH) with a wire coating

Production tolerance:According to DIN 2095 class 2, DIN 2097 class 2

RoHS:The antenna is in accordance with the RoHs standard from deliveries after 01/06/2006

Examples:

Part Number: ANT868HEL- 9.5 - HOR- AgSilver plated 868 MHz helical antenna horizontal variant (no bend on the soldering pin 9.5 turnsWe can supply you helicals with number of turns according to your demand.

Part Number: ANT433VER- 15.5 - VER- AgSilver plated 433 MHz vertical antenna vertical variant (bend on the soldering pin 15.5 turnsWe can supply you helicals with number of turns according to your demand.

Important notes:Helical antennas are a unipole antenna type. All antennas of this type need a ground plane area with a radius min. lambda/4 to reach optimal antenna parameters. It results from physical principles about electromagnetic waves radiation. If there is any different matter than air, the antenna impedance, SWR, and radiation diagram are changed. It could be quite essentially from the antenna optimal values. That is the reason why there should not be placed any conductive and also non conductive objects in near antenna surroundings. In the cases, that it is impossible to ensure this condition (from mechanical reasons), we recommend verifying the antenna parameters and turns trimming at a skilled work place. We are able to provide you with like this test and determinate optimal wire length number of turns before production. In this case a sample / prototype of your casing including mechanical parts and PCB is necessary.Antenna is a source of electromagnetic radiation. It can have an influence on other electronic circuits placed in its surroundings. Manufacturer of the final product have to ensure the circuit immunity against the electromagnetic radiation. Manufacturer also has to determinate operation conditions of the final product in order to exclude any potential damages, which could be due to the radiation on health and other subjects.

Helical coating wire antennas868 MHz Helical antenna:433 MHz Helical antenna:Variants and ordering information:868 MHz Helical antenna:433 MHz Helical antenna:Important notes: