What Antenna Polarization should I use?
Most Point-to-Multipoint WLAN systems use V-Pol
(vertical polarization). This allows the use of
inexpensive vertical omnidirectional antennas.
Higher-density areas are beginning to use more HPol (horizontal polarization) antennas for PtMP.
Point-to-Point (backhaul) systems may use either
vertical or horizontal polarization as long the same
polarization is used at each end. Horizontal
polarization may perform slightly better when
transmitting through a forested area, otherwise
there is very little difference in propagation
effects. Most standard Telex Wireless antennas
are vertical polarization except -H versions of the
dish antennas and the 2445AA sector
antenna. The 2401 patch antenna may be mounted
for either polarity.
Will CP (circular polarization) help my system?
Normally, a WLAN or WISP has a set of channels
or frequency sets that are either vertically-polarized
or horizontally-polarized, or some of each. Since
the CP antenna responds (theoretically) equally to
either polarization at a level of 3 dB down from
maximum signal, there is not much reason to add
CP to a system that already has vertical, horizontal
or both polarizations. This won't gain additional
spectrum for the WISP. Polarization discrimination
is generally a good thing, and CP antennas have
no discrimination against linear-polarized signals or
interference. However, CP antennas do work well
in situations where the polarization is not pure
vertical or pure horizontal, such as in downtown
areas with lots of multiple reflections from
buildings, airborne applications, over-water
systems and indoor applications where the client
antenna can be either vertical or horizontal or
anywhere in between (such as a laptop or PDA
antenna). The Telex 2405 ceiling-mount antenna
works great in these indoor situations.
What is the Half-Power beamwidth?
" In a radiation pattern cut containing the direction
of the maximum of a lobe, the angle between the
two directions in which the radiation intensity is
one-half the maximum value". The Half-power
beamwidth is also commonly referred to as the 3dB beamwidth. Beamwidth typically decreases as
antenna gain increases.
What is VSWR?
VSWR stands for Voltage Standing Wave Ratio. It
is the ratio of the maximum/minimum values of
standing wave pattern along a transmission line to
which a load is connected. VSWR value ranges
from 1 (matched load) to infinity for a short or an
open load. For most WLAN antennas the maximum
acceptable value of VSWR is 2.0. VSWR of 1.5 or
less is excellent. This is approximately the same as
a Return Loss of 14.5 dB. What this means is that
most of the signal from the transmitter to the
antenna is being radiated. (96% radiated and 4%
reflected) A VSWR of 2.0 (return loss of 9.5 dB)
means that 90% is radiated and 10% reflected.
What is a Yagi antenna and how is it
different from a panel?
A Yagi-Uda antenna array, commonly called a
Yagi, is made up of linear wire or rod-type
elements, each having a length of approximately
1/2 wavelength. These elements are arranged in a
row, with each element parallel to each other. The
rear element in this array is called the reflector.
The second element is the driven element, which is
connected to the transmission line, and all other
elements in front of the driven are called directors.
The gain of a single Yagi antenna ranges from
about 6 to 20 dBi, depending upon the length of the
array. Multiple Yagi antennas may be connected
together side by side in larger arrays, which may
have gains from 10 to 26 dBi or higher. A single
Yagi antenna has a long, narrow profile and UHF
yagis are usually enclosed in radome tubes to
protect them from the environment. Gain, sidelobe
and F/B performance of a Yagi antenna is very
similar to a panel antenna. The main differences
are the appearance and that single Yagi antennas
have approximately the same beamwidth in each
plane, while a panel may be designed for different
beamwidths in each plane. For more information
on Yagi antennas
How much power can I transmit on a 2.4 GHz 10 dBi omni and still
be legal?
The FCC regulations for PtMP allows only 36 dBm
(4 watts) EIRP. This is 30 dBm (1 watt) into a 6 dBi
antenna. If you use a 10 dBi antenna, you must
limit your transmitter (or amplifier) to 26 dBm (10 +
26 = 36 dBm). For a 14 dBi panel antenna, this
allows a 22 dBm transmitter (or amplifier). Power is
measured at the antenna connector, so subtract
any cable loss between the amplifier and the
antenna. Refer to the following table:
Power at antenna
(dBm/Watts)
Antenna Gain
(dBi)
EIRP
(dBm)
EIRP
(watts)
30 dBm (1 W)
6
36
4
27 dBm (500 mW)
9
36
4
24 dBm (250 mW)
12
36
4
21 dBm (125 mW)
15
36
4
18 dBm (62 mW)
18
36
4
15 dBm (31 mW)
21
36
4
12 dBm (15 mW)
24
36
4
Can I use any antenna of my choice for my AP
or CPE antenna?
The strictly legal answer is NO. According to FCC
Part 15 Section 15.204 "Only the antenna with
which an intentional radiator is authorized may be
used with the intentional radiator". Those people in
countries other than the US will need to consult
their own regulations. If you are not sure if the
antenna that you plan to use is certified with the
radio system, ask the radio or antenna
manufacturer/vendor. If you have the radio FCC ID,
you can check on the FCC web site for certification
information. Some older certifications are not
available on this site.
How much power can I transmit with in my
2.4 GHz Point-to-Point system?
According to FCC regulations, 2.4 GHz Part 15.247
point-to-point transmitters may use a 30 dBm
transmitter with a 6 dBi antenna. For a 3 dB
increase in antenna gain, the transmitter power
output must be reduced by 1 dB. Power is
measured at the antenna connector, so subtract
any cable loss between the amplifier and the
antenna. Refer to the following table. (also see
Canadian Rules)
Power at antenna
(dBm/watts)
Max Antenna Gain
(dBi)
EIRP
(dBm)
EIRP
(watts)
30 dBm (1 W)
6
36
4
29
9
38
6.3
28
12
40
10
27 dBm (500 mW)
15
42
16
26
18
44
25
25
21
46
39.8
24 dBm (250 mW)
24
48
63
23
27
50
100
22
30
52
158
Is the Customer or Client (CPE) system
considered PtMP or PtP?
If the CPE system (or Subscriber Unit - SU) only
talks with the POP/AP and is at a fixed location,
then it is considered to be PtP and can use power
and antenna gain associated with PtP systems, as
shown below. (This has been verified by
FCC Certified systems using a 26 dBm radio and a
17 dBi antenna) If a CPE system is part of a mesh
network, then it is considered PtMP.
Should I use 2.4 GHz or 5.8 GHz for my
WLAN or WISP system?
Currently, most systems use either IEEE 802.11 or
802.11b operating between 2.4 and 2.4835 GHz.
As these frequencies become more congested, the
U-NII Band 3 at 5.725 - 5.825 GHz (IEEE 802.11a)
will be used more. 5.8 GHz also offers data
transmission rates greater than 11 MB/s.
However, more antenna gain will be necessary at
5.8 GHz for the same distance on 2.4 GHz. 5.8
GHz will have a smaller Fresnel zone, so there
may be certain advantages when shooting a signal
through a tight space between trees or buildings.
The WCS and MMDS frequencies between 2.1 and
2.7 GHz are also available to FCC-licensed
users. (See IEEE 802.16a)
How do I know which antenna to select for my outdoor WLAN
/WISP access point?
This depends on how your subscribers or clients
are located with respect to the access point and
what type of terrain is in between. You can place
an omnidirectional antenna such as our Telex
Wireless model 2439 (10 dBi gain) near the middle
of your group of clients at a hub (Access Point)
location. This works best if your facilities/customers
are no more than 6 miles (9.5 km) from the hub
and unobstructed by hills, trees or buildings. You
may also select to use several sector antennas at
an AP location. Our model 2443 (12 dBi 120
degree panel) or model 2444 (14 dBi 90 degree
panel) antennas work great for distances up to 12
miles (19.4 km) with clear LOS or up to 6 miles
with some trees and buildings in the path. Greater
distances may be obtained by using towermounted amplifiers with antenna heights above
100 feet HAAT. Whichever antenna you choose,
please make sure that it is Industry Canada or FCC
certified with your radio!
How high should I place my outdoor Access
Point antennas?
This depends upon a lot of factors. If you have a
building with roof access, this is usually the best
option, since the feedline losses may be minimized
if the equipment can be placed near the antennas.
A minimum height is usually around 75 feet. This
places the antennas above most trees. This height
will also give a radio horizon of approximately 12
miles, assuming flat terrain. If you have taller trees,
or tall buildings nearby, you may wish to use an
antenna height of 200 feet or more. This gives a
radio horizon of 14 miles. As towers may fall under
local zoning ordinances, you may also wish to
consider water towers, grain elevators or utility
poles as other options. Placing AP antennas higher
than 100 feet exposes them to greater amounts of
interference, more feedline losses, zoning
restrictions, FAA lighting requirements, and larger
cell areas. Existing towers may be located using
these sites - TelecomSiteSource, FCC Antenna
Structure Registration and Wireless Radio Tower
Locator. Grain elevators may be located using this
site - Grain Elevator Locator.
What antennas should I use for Point-to-Point data transmission?
Directional antennas should be used for point-topoint transmission. The type of directional antenna
depends upon the power output, cable type and
length, height, distance, data rate and terrain. We
recommend the use of a range table to estimate
the antenna types. Whichever antenna
you choose, make sure that it is FCC certified
with your radio!
Is the Customer or Client (CPE) system
considered PtMP or PtP?
If the CPE system (or Subscriber Unit - SU) only
talks with the POP/AP and is at a fixed location,
then it is considered to be PtP and can use power
and antenna gain associated with PtP systems, as
shown below. (This has been verified by
FCC Certified systems using a 26 dBm radio and a
17 dBi antenna) If a CPE system is part of a mesh
network, then it is considered PtMP.
Is it safe to work or stand near an active PtP
WLAN antenna?
RF safety is always a concern when working
around microwave radiation. The FCC has set
safety standards that are meant to guard against
potentially harmful RF fields. In a "controlled"
environment (where the people near the antenna
know of the hazards), the FCC limit is 5.0
mw/cm^2. In an "uncontrolled" environment
(where the people near the antenna are unaware),
the FCC limit is 1.0 mw/cm^2. These limits are
directly related to the EIRP of the antenna system
along the main beam. Other frequencies and
powers may be calculated at this site: RF safety
Here are some other excellent links: ARRL - RF
Exposure, ARRL - RF Safety, FDA, WLANA Health
At 2450 MHz
EIRP of antenna
system
(dBm)
Min. Safe Distance in
a
Controlled
Environment
(feet)
Min. Safe Distance in an
Uncontrolled
Environment
(feet)
36
0.31
0.63
40
0.46
0.98
42
0.57
1.22
44
0.71
1.52
46
0.88
1.90
48
1.09
2.37
How do I perform a PtP site survey?
Initially, create a path profile using one of the
various mapping programs. If LOS and Fresnel
zone clearance seems good, check for trees and
other unusual obstacles to LOS. A good way to
check this is to place a person at each end of the
path with a high-powered flashlight and a cellphone. While talking with each other, flash the light
so that the other person can see it. UHF hand-held
radios (FRS or commercial frequencies) also work
well to determine LOS. Use 1 watt radios for up to
4 miles and 5 watt radios for up to 15 miles. If
results look promising, place an AP at one end and
a CPE at the other and try connecting using 19-24
dBi grid or panel antennas. (Do not swing both
directional antennas at the same time!) Look for
interference at each end by using a spectrum
analyzer and both vertical and horizontal polarized
antennas. If you have Teletronics radios, here is a
neat site-survey tool. There are also professional
consultants (e.g. Cyber-Doctors) that can perform
wireless site surveys for a fee. Site Survey tools
are available on the AeroNet wireless broadband
site.
What is the Maximum Distance for a PtP
link?
The maximum distance for a standard 802.11b PtP
(or PtMP) path is approximately 12 miles. This is
primarily due to timing issues in the 802.11b
firmware. Other operating systems, such as
KarlNet TurboCell, Orinoco COR or StarOS can
overcome this limit and produce links up to 70
miles, depending upon terrain.
How do I perform a PtP site survey?
Initially, create a path profile using one of the
various mapping programs. If LOS and Fresnel
zone clearance seems good, check for trees and
other unusual obstacles to LOS. A good way to
check this is to place a person at each end of the
path with a high-powered flashlight and a cellphone. While talking with each other, flash the light
so that the other person can see it. UHF hand-held
radios (FRS or commercial frequencies) also work
well to determine LOS. Use 1 watt radios for up to
4 miles and 5 watt radios for up to 15 miles. If
results look promising, place an AP at one end and
a CPE at the other and try connecting using 19-24
dBi grid or panel antennas. (Do not swing both
directional antennas at the same time!) Look for
interference at each end by using a spectrum
analyzer and both vertical and horizontal polarized
antennas. If you have Teletronics radios, here is a
neat site-survey tool. There are also professional
consultants (e.g. Cyber-Doctors) that can perform
wireless site surveys for a fee. Site Survey tools
are available on the AeroNet wireless broadband
site.
What connectors does Telex use?
Telex can supply antennas with almost any
connector, or even without a connector for OEM
applications. Standard connectors are Type N plug,
Type N Jack, TNC, RP-TNC, SMA, RP-SMA, MCCard, and MMCX. Cable size dictates which
connectors may be used on certain antennas. LAN
Administrators and ISP's should check with the
manufacturer of the WLAN system hardware
before adding new cables and connectors!
What do you recommend for weatherproofing
connectors?
We recommend 3M vinyl electrical tape for most
applications. Apply one layer of high-quality 3M
(88+) tape, then one layer of mastic, then a final
layer of 3M tape. (Hint: Apply the first layer of tape
with the sticky surface out) Do not use any sprayon or brush-on weather-proofing material, as this is
VERY difficult to remove. Times Microwave
supplies both vinyl mastic weatherproofing kits as
well as 3M cold-shrink weatherproofing kits. See
the LMR hardware accessories at the Times
Microwave LMR-series web site. Andrew also
supplies cold-shrink weatherproofing kits and
WeatherShield snap-on connector housings for
their Heliax cables. See page 472, 499 and 509 of
their catalog at the Andrew Heliax web site.
What do you recommend for antenna
grounding & lightning protection?
This depends upon the type of installation. For
tower-mounted antennas, there should be a good
ground wire (#2/0) attached between the tower
base and a single-point earth ground. (There is no
need for a separate ground wire running along the
tower!) For roof-mounts, the mast should be
grounded to the steel structure of the building if
possible. If no connection to the building is
possible, then a large diameter wire may be run
directly to earth ground. Lightning arrestors should
be added to the coax cable between the antenna
and the amplifier or other radio equipment unless
built-in to the amplifier or radio. Otherwise, they
should normally be installed where the coax enters
a building. For more information, see technical
documents at PolyPhaser. Here is a sample
lightning arrestor from Alpha-Delta. Arrestors may
be ordered through ALLCOM or TESSCO. Data
lines running from the antenna must also be
protected from lightning surges. We recommend
the Tripplite and APC ProtectNet line of surge
suppressors. These should be installed where the
line enters the house, in a weather-protected area.
If you use PoE, then choose a suppressor model
rated for T1 service with a voltage-clamp at 75
volts or higher.
How can I check the VSWR of my antenna
before and after installation?
The VSWR (Voltage Standing Wave Ratio) of a 2.4
GHz antenna may be checked with most
HP/Agilent or Anritsu RF Network Analyzers that
have a maximum frequency of 3 GHz. Lower-cost
hand-held units are also available from Anritsu and
Bird Electronics. The Anritsu S332B Sitemaster /
Spectrum Analyzer combo has both VSWR and
Spectrum Analyzer features in one unit. It is also
possible to use an IFR spectrum analyzer for return
loss (VSWR) measurements. The WLANexpert
also has VSWR measurement capabilities for
PRISM chipset-based cards. Antennas at this
frequency may be checked with an
attached transmission line no longer than: 25 feet
(LMR-400 & 600), or 5 feet (LMR-195 & RG-58).
Longer cables will make the VSWR appear much
lower than it really is. When testing an antenna
before installation, make sure that the antenna is
outdoors and pointing away from the ground and
any metallic objects. A VSWR of less than 1.5:1
is excellent, and less than 2:1 is acceptable. Most
antenna manufacturers spec their antennas for
either 1.5:1 or 2:1 across the bandwidth.
Should I use 2.4 GHz or 5.8 GHz for my
WLAN or WISP system?
Currently, most systems use either IEEE 802.11 or
802.11b operating between 2.4 and 2.4835 GHz.
As these frequencies become more congested, the
U-NII Band 3 at 5.725 - 5.825 GHz (IEEE 802.11a)
will be used more. 5.8 GHz also offers data
transmission rates greater than 11 MB/s.
However, more antenna gain will be necessary at
5.8 GHz for the same distance on 2.4 GHz. 5.8
GHz will have a smaller Fresnel zone, so there
may be certain advantages when shooting a signal
through a tight space between trees or buildings.
The WCS and MMDS frequencies between 2.1 and
2.7 GHz are also available to FCC-licensed
users. (See IEEE 802.16a)
What effect does rain and ice have on antennas and cables?
Rain will have no effect upon antennas protected
within radomes. The radomes must also have a
drain hole for condensation drainage. However,
Yagi antennas without radomes are highly
vulnerable to rain, as the rain drops will accumulate
on the elements and detune the performance. (The
droplets actually make each element look longer
than it really is!) Water intrusion in coaxial cable
will increase the cable losses significantly and raise
the VSWR at the transmitter. (See the next
question for weatherproofing suggestions) If the
link does not come back up after the rain
evaporates, then you probably have a waterintrusion problem in the cable. Sometimes you can
open both ends of a cable and measure a very
small voltage across the center conductor to shield
(< 100 mV) if water is inside the cable. This is
caused by galvanic action between dissimilar
conductors with water as the electrolyte. Ice
accumulation on exposed elements can cause the
same detuning effect as rain, however it stays
around longer. Radomes will protect the radiator
from most of these effects, however if the radome
surface is very close to the radiator and/or the ice
is very thick, then the VSWR may be impaired. Ice
can also damage antennas if it falls on the antenna
from a higher structure or tree.
How can I check the VSWR of my antenna
before and after installation?
The VSWR (Voltage Standing Wave Ratio) of a 2.4
GHz antenna may be checked with most
HP/Agilent or Anritsu RF Network Analyzers that
have a maximum frequency of 3 GHz. Lower-cost
hand-held units are also available from Anritsu and
Bird Electronics. The Anritsu S332B Sitemaster /
Spectrum Analyzer combo has both VSWR and
Spectrum Analyzer features in one unit. It is also
possible to use an IFR spectrum analyzer for return
loss (VSWR) measurements. The WLANexpert
also has VSWR measurement capabilities for
PRISM chipset-based cards. Antennas at this
frequency may be checked with an
attached transmission line no longer than: 25 feet
(LMR-400 & 600), or 5 feet (LMR-195 & RG-58).
Longer cables will make the VSWR appear much
lower than it really is. When testing an antenna
before installation, make sure that the antenna is
outdoors and pointing away from the ground and
any metallic objects. A VSWR of less than 1.5:1
is excellent, and less than 2:1 is acceptable. Most
antenna manufacturers spec their antennas for
either 1.5:1 or 2:1 across the bandwidth.
Antennas are everywhere allowing information to flow seamlessly from one
source to another. Telex Wireless Networking Technology is the best choice for
wireless solutions. With trusted innovation going into each design our antennas
not only lead the way, but also stand the test of time.
We hope that our Web site helps to illustrate our products' application, and also
provides useful information on utilizing the technology behind wireless solutions.
In an effort to make the site easy to use we have developed market pages to
help guide you as you research the appropriate antenna, as well as a complete
list of product families on the tab above. Please feel free to contact us if you have
trouble navigating the site, or are unable to find the information you are seeking.
Telex has many different types of antennas for the 2.400 to 2.500 GHz
unlicensed band, including Omni, Yagi, Sector, Dish and Patch antenna designs.
These antennas are used for data PtP and PtMP applications in Wi-Fi, 802.11b,
802.11g, ISM and fixed-wireless systems. Many of these antennas are included
in FCC Certified radio systems.

Home

Hotels

Military

Healthcare

Education

Distribution

Government

Warehousing

Manufacturing

Small Business

Convention Centers

Corporate Enterprises

Internet Service Providers

Telecommunications Companies
Luxul's antenna technology is unsurpassed when compared to conventional antennas. We
consistently outperform any other point-to-multipoint, wireless LAN or point-to-point antenna on
the market. We accomplish this by offering:








Wider signal coverage
Lower costs
Scalability
Stronger signal strength and quality
Superior penetration
Operating in non-line of sight environments
Better throughput
More reliable performance in inclement weather
Circular Polarized antennas are designed so that they respond equally to either vertically or
horizontally polarized signals in indoor and outdoor environments. CP antennas are either Left-
Hand CP (LHCP) or Right-Hand CP (RHCP), and can be either Omni-directional or Directional.
The 2405 is a 5 dBic wide-angle directional CP patch for 2.4 GHz. The 2405 is an excellent
choice for a low profile wall or ceiling-mounted antenna. It is designed to be mounted to a flat
surface by screws, adhesive strips or an optional ceiling-rail bracket. The polarization is LHCP, so
that it will respond equally to either vertically or horizontally polarized signals in a typical indoor
environment.