ANT-418-HESM Data Sheet by Product Description HE Series antennas are designed for direct PCB 8.89 mm Outside (0.35 ) mounting. Thanks to the HEs compact size, they Diameter are ideal for internal concealment inside a products housing. The HE is also very low in cost, making it Inside 6.35 mm well suited to high-volume applications. HE Series Diameter (0.25 ) antennas have a very narrow bandwidth thus, care in placement and layout is required. In addition, they are not as efficient as whip-style antennas, so they are generally better suited for use on the Wire transmitter end where attenuation is often required Diameter anyway for regulatory compliance. Use on both 1.27 mm (0.05 ) transmitter and receiver ends is recommended only in instances where a short range (less than 30% of whip style) is acceptable. 38.10 mm (1.50 ) Features Very low cost Recommended Mounting Compact for physical concealment Precision-wound coil No electircal No ground plane or traces Rugged phosphor-bronze construction connection on this under the antenna pad. For physical Surface-mount 38.10 mm support only. (1.50 ) Electrical Specifications Center Frequency: 418MHz 7.62 mm (0.30 ) Recom. Freq. Range: 393443MHz 3.81 mm 12.70 mm Wavelength: -wave (0.15 ) (0.50 ) VSWR: 2.0 typical at center Peak Gain: 1.7dBi Impedance: 50-ohms Connection: Surface-mount Oper. Temp. Range: 40C to +80C Electrical specifications and plots measured on a 7.62 cm x Ground plane on 50-ohm microstrip line 19.05 cm (3.00 x 7.50 ) reference ground plane bottom layer for counterpoise. Ordering Information ANT-418-HESM (helical, surface mount) 1 Revised 5/16/16Counterpoise Quarter-wave or monopole antennas require an associated ground plane counterpoise for proper operation. The size and location of the ground plane relative to the antenna will affect the overall performance of the antenna in the final design. When used in conjunction with a ground plane smaller than that used to tune the antenna, the center frequency typically will shift higher in frequency and the bandwidth will decrease. The proximity of other circuit elements and packaging near the antenna will also affect the final performance. For further discussion and guidance on the importance of the ground plane counterpoise, please refer to Linx Application Note AN-00501: Understanding Antenna Specifications and Operation. VSWR Graph VSWR 1.429 Reflected Power 3:1 25% 2:1 11% 1:1 0% 318MHz 418MHz 518MHz What is VSWR The Voltage Standing Wave Ratio (VSWR) is a measurement of how well an antenna is matched to a source impedance, typically 50-ohms. It is calculated by measuring the voltage wave that is headed toward the load versus the voltage wave that is reflected back from the load. A perfect match will have a VSWR of 1:1. The higher the first number, the worse the match, and the more inefficient the system. Since a perfect match cannot ever be obtained, some benchmark for performance needs to be set. In the case of antenna VSWR, this is usually 2:1. At this point, 88.9% of the energy sent to the antenna by the transmitter is radiated into free space and 11.1% is either reflected back into the source or lost as heat on the structure of the antenna. In the other direction, 88.9% of the energy recovered by the antenna is transferred into the receiver. As a side note, since the :1 is always implied, many data sheets will remove it and just display the first number. How to Read a VSWR Graph VSWR is usually displayed graphically versus frequency. The lowest point on the graph is the antennas operational center frequency. In most cases, this will be different than the designed center frequency due to fabrication tolerances. The VSWR at that point denotes how close to 50-ohms the antenna gets. Linx specifies the recommended bandwidth as the range where the typical antenna VSWR is less than 2:1. 159 Ort Lane, Merlin, OR, US 97532 Phone: +1 541 471 6256 Data Sheet ANT-418-HESM 2 Fax: +1 541 471 6251 by www.linxtechnologies.com