RXM-900-HP-II Linx Technologies Inc, RXM-900-HP-II Datasheet - Page 17

• Manufacturer Part Number: RXM-900-HP-II
• Description: RECEIVER RF 900MHZ 8-CH PACK
• Manufacturer: Linx Technologies Inc

Specifications of RXM-900-HP-II

• Frequency: 902MHz ~ 928MHz
• Sensitivity: -95dBm
• Data Rate - Maximum: 50 kbps
• Modulation Or Protocol: FM, FSK
• Applications: Home / Industrial Automation, Remote Access, Security Alarms
• Current - Receiving: 18mA
• Data Interface: PCB, Through Hole
• Antenna Connector: Through Hole
• Voltage - Supply: 2.7 V ~ 16 V
• Operating Temperature: 0°C ~ 70°C
• Package / Case: 18-SIP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Features: -
• Memory Size: -
• Other names: RXM-900-HP2; RXM-900-HP2

Whip Style
1/4-wave wire lengths
for HP frequencies:
902-928MHz = 3.06"
ANTENNA STYLES
From a coat hanger to a tuned Yagi, there are literally hundreds of antenna styles
and variations that can be employed. Following is a brief discussion of the styles
most commonly utilized in compact RF designs. The selection chart broadly
categorizes key areas of antenna performance. In reviewing this section it is
important to recognize that each antenna style will produce widely varying
results based on the specific design execution and optimization. Additional
information can be found in Linx application notes #00500, #00100, #00125 and
#00140.
A whip-style antenna provides exceptional performance and is
easy to integrate. A low-cost whip is generally made of a wire or
rod while more expensive whip designs are encapsulated in
rubber or plastic to improve appearance and minimize the
potential for damage to the antenna element. A whip is often
combined with a helical winding to reduce the overall length.
This technique is commonly referred to as “base loading”.
Every frequency has a physical length that it occupies in space.
That length is referred to as the wavelength and is theoretically
determined by two factors: 1) the frequency itself and 2) the
speed of propagation. The wavelength of the frequency to be
received or transmitted determines an antenna’s length. Since
an antenna has a dielectric constant greater than that of free
space, the velocity of a wave on the antenna is slower. This fact,
along with several other factors, has led antenna designers to
accept the formula below as an accurate starting point for
determining the physical length of a half-wave antenna. The
resultant length may be divided in half for a quarter wave.
Because of its compact length, a popular
antenna style for Part 15 applications is the
1/4-wave whip. It is important to note that in
order to operate effectively the 1/4 wave
must radiate against a ground-plane. The
ground-plane can be a metal case or
ground area on a PCB of at least equivalent
area to the antenna’s surface. The ground-
plane acts as a counterpoise, in essence
forming an effective half-wave dipole as
illustrated.
There are many manufacturers providing high-quality whip
antennas. It is important to remember, however, that Part 15
requires a permanent attachment or attachment with a unique
or not commonly available connector. This rules out the use of
whips employing standard connectors such as BNC's.
L =
F
234
MHz
Where:
L=length in feet of quarter-wave length
F=operating frequency in megahertz
VERTICAL /4 GROUNDED
VIRTUAL /4
ANTENNA (MARCONI)
GROUND
DIPOLE
I
E
PLANE
DIPOLE
ELEMENT
/4
/4