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1 Revised 1/26/15
Product Description
Designed for permanent attachment, PW Series
¼-wave whips give outstanding performance in a
rugged and cost-effective package. The antenna
is attached by placing its base through a ¼" (6.35
mm) hole in the product and securing it with a
nut or by threading it into a PEM-style insert. The
antenna is fed through the base with 8.5" (216
mm) of coax cable. Straight-cut RG-174 allows the
addition of any 50-ohm RF connector or allows the
cable to be soldered directly to the PCB, saving
the cost of the connector. It is also available with
1.32 mm coax cable terminated with a U.FL /
MHF compatible connector. This saves the labor
of adding a connector while using one that is small
enough to fit through the antenna’s mounting hole.
Custom lengths and terminations are available by
special order.
Features
• Low cost
• Outstanding performance
• Omni-directional pattern
• Wide bandwidth
• Flexible main shaft
• Rugged & weatherized
• Integral 8.5" (216 mm) RG-174 coax cable or
1.32 mm coax (U.FL)
• Use with plastic* or metal enclosures
* Requires proximity ground plane
Electrical Specifications
Center Frequency: 868MHz
Bandwidth: 750–950MHz
Wavelength: ¼-wave
VSWR: 1.9 typical at center
Peak Gain: 1.6dBi
Impedance: 50-ohms
Connection: Straight-cut or U.FL/MHF
Cable: 8.5" (216 mm) RG-174 coax
cable or 1.32 mm coax (U.FL)
Oper. Temp. Range: –40°C to +90°C
Electrical specifications and plots measured on 10.16 cm x 10.16 cm
(4.00" x 4.00") reference ground plane
ANT-868-PW-QW-xxx
Data Sheet by
Ordering Information
ANT-868-PW-QW (with straight cut RG-174 coax)
ANT-868-PW-QW-UFL (U.FL/MHF compatible
connector)
6.0 mm
(0.24")
7.8 mm
(0.31")
13.0 mm
(0.51")
84.0 mm
(3.31")
4.5 mm
(0.18")
1/4-28
UNF
14.5 mm
(0.57")
52.0 mm
(2.05")
End
View
I-PEX silhouette
shown in shadow
Straight Cut or U.FL
216 mm
(8.5")
7/16"
HEX
AniennaFactor Llfix
2
by
Data Sheet ANT-868-PW-QW-xxx
VSWR Graph
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 antenna’s 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.
Counterpoise
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 Reflected Power
3:1
2:1
1:1
25%
11%
0%
868MHz 968MHz768MHz
1.557