Question:
I work for a large construction company in Boston...We use handheld radios
on the jobsites...they are made by Motorola...they have incredible
receiving/transmitting range (up to about 50 miles)...I am curious as to
why they are able to transmit and receive over such long distances. I know
that some towers are involved, because when the radios don't work, we call
up the folks who we rent them from, and they claim the "tower is down".
How does all this stuff work? also, what frequencies are these usually
located?
Answer:
If it's true regarding the range and the use of towers, it seems your
company rents commercial radios that are either "trunked" or on a
standard repeater system. Most likely they're "trunked". These are
radios that use a system where the radio transmits on one frequency and
receives on another. The TX frequency is picked up by the tower and
retransmitted at a much higher power on another frequency for all other
users on the system to hear.
Most job sites use what are called "itinerant" frequencies and are not
on a repeater system. These usually have limited range of up to several
miles, but no further. Itinerant frequencies are usually but not
limited to: 151.625, 154.57, 154.600. There are several UHF
frequencies set aside for itinerant use as well.
The reason for the range (50 miles) is because the small power output
of a handheld is being REPEATED thru a repeater that runs much more
power. No low powered handheld (a few watts) will reach 50 miles.
