EVAL-315-LT Linx Technologies Inc, EVAL-315-LT Datasheet - Page 3

• Manufacturer Part Number: EVAL-315-LT
• Description: KIT EVAL FOR LT SERIES 315MHZ
• Manufacturer: Linx Technologies Inc
• Series: LTr
• Type: Transceiver, Transcoderr

Specifications of EVAL-315-LT

• Frequency: 315MHz
• Product: RF Development Tools
• Maximum Frequency: 315 MHz
• Supply Voltage (max): 3 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: LT Series RF Modules - 315MHz
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

RANGE TESTING
ABOUT ANTENNAS
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Several complex mathematical models exist for determining path loss in many
environments. These models vary as the transmitter and receiver are moved
from indoor operation to outdoor operation. Although these models can provide
an estimation of range performance in the field, the most reliable method is to
simply perform range tests using the transmitter and receiver in the intended
operational environment.
Basic range testing can be performed with the transceiver evaluation boards. To
prepare the board for range testing, turn it on by switching the power switch to
the ON position. Pressing S0 or S2 will activate the buzzer on the receiver board,
while S1 or S3 activates the LED. The CONFIRM LED provides an indication
that the signal has traveled round trip, so only one person is needed to conduct
range testing.
As you near the maximum range of the link in your area, it is not uncommon for
the signal to cut in and out as you move. This is normal and can result from other
interfering sources or fluctuating signal levels due to multipath effects. This
results in cancellation of the transmitted signal as direct and reflected signals
arrive at the receiver at differing times and phases. The areas in which this
occurs are commonly called “nulls” and simply walking a little farther will usually
restore the signal.
Since the evaluation boards are intended for use by design engineers, they are
not FCC certified. The transmitter section has been attenuated to approximate
legal limits by resistor R9, so that the range test results will approximate the
results from a well-designed, certified product. For applications where Part 15
limits are not applicable, or output levels can be legally raised due to protocol
duty cycle, R9 can be changed according to the Output Power vs. LADJ
Resistance graph in the LT Series Transceiver Data Guide.
To achieve maximum range, keep objects such as your hand away from the
antenna and ensure that the antenna on the transmitting board has a clear and
unobstructed line-of-sight path to the receiving board. Range performance is
determined by many interdependent factors. If the range you are able to achieve
is significantly less than what is specified by Linx for the products you are testing,
then there is likely a problem with either the board or the ambient RF
environment in which the board is operating. First, check the battery, switch
positions, and antenna connection. Next, measure the transceiver’s RSSI
voltage with the other transceiver turned off to determine if ambient interference
is present. If this fails to resolve the issue, please contact Linx technical support.
The choice of antennas is one of the most critical, and often overlooked, design
considerations. The range, performance, and legality of an RF link are critically
dependent upon the type of antenna employed. Linx offers a variety of antenna
styles that you may wish to consider for your design. Included with your kit are
HD Series (315MHz) or CW Series (418MHz and 433MHz) connectorized whip
antennas that should be connected prior to using the kit. Despite the fact that the
antenna is not centered on the board’s ground plane, it exhibits a VSWR of <1.7
and suitably demonstrates the module’s best practical performance.
USING THE BOARDS AS A DESIGN REFERENCE
IN CLOSING
The basic evaluation boards included in this kit are very simple, yet they illustrate
some important techniques that you may wish to incorporate into your own board
layout. You will observe that the LT mounting pads extend slightly past the edge
of the part. This eases hand assembly and allows for better heat conduction
under the part if rework is necessary. Next, observe the use of a full ground
plane fill on the lower side of the board. This ground plane serves three important
purposes:
First, since a 1/4-wave antenna is employed, the ground plane is critical to serve
as a counterpoise (you may wish to read Application Notes AN-00500 and AN-
00501 for additional details on how a ground plane affects antenna function).
Second, a ground plane can help minimize the transfer of noise between stages
of a product, as well as unintentional radiation of noise into free space.
Third, a ground plane allows for the implementation of a microstrip feed to the
antenna. The term microstrip refers to a PCB trace running over a ground plane
that is designed to serve as a 50-ohm transmission line between the module and
the antenna. A microstrip is implemented on this evaluation board. If you are
unfamiliar with microstrip calculations, you may wish to refer to the LT Series
data guide or the calculator available on our website, www.linxtechnologies.com.
Here at Linx, “Wireless Made Simple” is more than just our motto, it is our
commitment. A commitment to the highest caliber of product, service, and
support. That is why, should you have questions or encounter any difficulties
using the evaluation kit, you’ll be glad to know many resources are available to
assist you. First, check carefully for the obvious, then visit our website at
www.linxtechnologies.com. Our website is organized in an intuitive format to give
you the answers you need. Day or night, the Linx website gives you instant
access to the latest information regarding the products and services of Linx. It’s
all here: manual and software updates, application notes, a comprehensive
knowledgebase, FCC information, and much more. If questions remain, call 541-
471-6256 between 8AM and 4PM Pacific Time to speak with an application
engineer.
Legal Notice
All Linx kits and modules are designed in keeping with high engineering standards;
however, it is the responsibility of the user to ensure that the products are operated in a
legal and appropriate manner. The purchaser understands that legal operation may require
additional permits, approvals, or certifications prior to use, depending on the country of
operation.
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