User's Manual

FT-512 Trailblazer Installation and User Manual version 1.09 10
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. It
is strongly recommended to avoid the use of 2.4GHz cordless phones in
the vicinity of Trailblazer products.
Local Area Network (Lan) Bridges
These devices are true spread spectrum devices, either a 1 MHz
bandwidth 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
Microwave oven outputs have been measured at levels up to +20dBm
ERP. This power consists of narrow pulses sweeping wildly in frequency
due to the circulators built into the ovens. The higher power spikes are
mostly concentrated in the upper half of the band between 2450 and 2485
MHz.
Fortunately few users of 2.4 GHz products are located in rural areas, leaving
sharing concerns down to consumer microwave ovens, LAN’s and other rural
telephone users. The functionality of the FT-512 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. All users in the band must accept all other signals within the
band, interfering or not.
How this impacts the CDMA/FDMA technology used in the FT-512:
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 bandwidth 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.