The surrounding terrain can affect reception in different ways.
If you are on flat land or water, reception will be at its
greatest. If you are in a mountain or canyon area, your scanner
will have trouble receiving radio signals or may not be able to
receive signals at all with the standard (rubber-ducky) antenna. To
overcome this limitation, you would need an external antenna. Learn
more about the different types of antennas that are available on
the market in our Scanner Accessories
page.
The type of antenna you are using plays a big part. If you are
using a standard rubber ducky antenna, you will not be able to pick
up distant signals then if you where using a telescoping or outdoor
antenna. Learn more about the different types of antennas that are
available on the market in our "Scanner Accessories"
publication available in the Radio Scanning Library.
If a radio is being used in simplex, or "talk-around"
mode, then that means that each radio is communicating directly to
the other radios on that frequency in that area. Simplex range can
vary from several blocks to several miles depending on how much
power the radios are putting out, the type and position of your
antenna, and the surrounding terrain. This range is typically 3-5
miles. For ranges beyond this limitation, a repeater system is
used.
A repeater is a device that is used to extend the range of
mobile and portable radios. Public safety agencies need to
communicate using portable or mobile radios over the distance
limitations posed by handheld and mobile radios, which is
approximately 3-5 miles. A repeater also allows communications
where buildings usually block the radio signals.
Generally, a repeater is placed on a building, radio tower,
mountain, or other tall structure. The higher up the repeater's
antenna, the larger coverage area, or range the signal will have.
The repeater works by listening to what the radios are transmitting
and simultaneously broadcast it back over a larger area. See the
publication "Type of Public Safety Radio Systems" in the
Radio Scanning Library for an overview of radio systems.
Lower frequencies behave different than higher frequencies.
Lower Frequencies travel farther giving you greater range. On the
flip side, higher frequencies travel shorter distances reducing
your range. Basically, you can hear signals in the 30MHz bands
much farther than frequencies in the 800MHz band.
Indoor reception will depend on what type of structure you are
in, wood, steel, or concrete. Generally, reception of lower
frequencies inside of a steel structure will be weak. Receptions of
higher frequencies within a steel structure are not generally
affected. Reception within a wood or concrete structure varies, but
is generally fair. If you are listening from home, connecting an
external antenna will boost your reception and extend the range of
reception. . Learn more about the different types of antennas that
are available on the market in our "Scanner Accessories"
publication available in the Radio Scanning Library.
Atmospheric conditions can affect range and reception. For
example, in the summertime, reception is stronger and range extends
farther than in the wintertime. The same goes for rainy days, where
range and reception can be slightly reduced.
Unusual occurrences where signals from hundreds, even thousands
of miles away are received. A skip, also called "sky wave
propagation", occurs when radio waves bounce off the
ionosphere and return to earth. Skips are most common in the summer
months and usually affect the VHF-Low band under 40 MHz or so.
Electrical devices can generate radio signals that can be picked
up by your scanner resulting in interference with existing
frequencies. Causes include electrical machinery, vehicle
ignitions, motors, power lines, florescent lights, etc.
Interference from electrical noise usually occurs with lower
frequencies.
Birdies are signals that are internally generated by a scanner
that can cause interference with some frequencies. The following is
a list of commonly known birdie frequencies. If you have a problem
with a birdie frequency, simply lock it out.
