User's Manual
Carlson Wireless USA revision 2.12 Page 6
(2) Other users of the 2.400 to 2.483 GHz ISM band.
The ISM or Industrial, Scientific, and Medical band, is shared with many
other type of services. Some examples follow:
Video Transmitters
These devices use analog radios which are usually fixed in frequency, 6
to 10 MHz bandwidth, low power with an ERP* of less then +10dBm.
Cordless phones
These devices are narrow band and fixed in frequency (during each use),
a 1 to 2 MHz bandwidth, low power with an ERP of less then +10dBm.
Local Area Network (Lan) Bridges
These devices are true spread spectrum devices, either a 1 MHz band-
width frequency hopping (FH) over the complete band or a CDMA type of
a 16 MHz bandwidth and stationary. ERP’s can range up into the +30’s
(dBm).
Microwave ovens
We have measured typical consumer microwave oven outputs at levels
up to +20dBm ERP. This consists of narrow less than 1 MHz wide spikes,
sweeping wildly in frequency due to the circulators built into the ovens.
The higher power spikes were mostly concentrated in the upper half of
the band between 2450 and 2485 MHz. Fortunately few of the users are
located in rural areas, leaving sharing concerns down to consumer micro-
wave ovens, LAN’s and other rural telephone users. The functionality of
the i-WLL Trailblazer system depends on the existing and forecasted
spectrum usage in the radio path. Due to the characteristics of the
spread spectrum radio, the ITU (International Telecommunication Union)
was able to coordinate this band globally for unlicensed use. This means
that any user has to accept all other users in this band, interfering or not.
How this impacts the CDMA/FDMA technology used in the I-WLL.
If the interfering signal is stationary and has a bandwidth less than 3 MHz
it will not create any significant problem even if it is 100 times (20dB)
stronger than the receive threshold. If the interfering signal has a band-
width wider than 4 MHz and is 10 times (10dB) stronger than the receive
threshold, it can render that channel(s) unusable. If the interfering signal
is hopping from frequency to frequency throughout the band such as the
Lan bridge device and is only 1/10 (–10dB) as strong as the receive
threshold, it can cause significant dropouts.
Carlson Wireless USA revision 2.12 Page 11
TROUBLESHOOTING
The outcome of the installation is dependent on the weakest link.
Five things are paramount to his system working well:
(1) An acceptable radio path
(2) Other users of the 2.4 GHz ISM band.
(3) Customer’s wiring of power and telephone circuits
(4) Antenna alignment within +/- 10 degrees for i-WLL-Trailblazer
(5) Quality of the telephone lines from the telephone company
(6) Quality of the power supplies.
If the system appears dead, with no tones audible on the subscriber
phone, look for a wiring fault. You can test for loop voltage at the FXS end
by measuring the voltage on each line. Each should be 30 VDC. Next
would be checking the DC current used by each unit. For example the
FXS unit with 16 Volts provided should draw (2W / 16V) ~125 mA. at idle
and ~300 mA with both lines off hook. This test is very useful to prove out
the wiring.
Next , check to see that the radio located under the daughter card is all
the way inserted into it’s socket by ejecting it and reinserting at the same
time seating the antenna connector into the radio.
Next, it will be important to confirm that a local test at the FXO base site
was done. If not, you will need to bring the FXS unit back to the base site
and temporarily connect the FXS unit up and confirm proper local opera-
tion.
If the system cuts in and out, or fails to draw dial tone, look for an align-
ment problem or path obstruction. Also you should check to see if not in a
rural area you may have a congested frequency band.
If you are having cross-talk between lines, examine the phone cabling
making sure it is individually twisted pairs, preferably with a Category 5
rating.
If after checking the above, you are still having problems please contact
our sales dept. for technical assistance by phone or email.
A note about the power supplies: The FXO unit will draw 2W off hook or
idle. The FXS will draw 2W idle and 4W with both lines off hook. We sug-
gest over-sizing the supplies by at least 3 times. For example a 15 volt
filtered DC switching type supply @ 1.00 Amp. It is much more likely to
survive power fluctuations and environmental temperatures and the extra
voltage above 12 allows for losses in the feed wire.