When it comes to a radio scanner’s ability to receive signals, there are many factors that affect the range (scanners maximum receivable distance) and reception (clarity of the signal received).
These factors include, but are not limited to the following:
- Line of Sight
- Surrounding Terrain
- Type of Antenna
- Repeated or Non-Repeated Stations
- Frequency Behavior
- Indoor Reception
- Atmospheric Conditions
- Skips/Propagation
- Electrical Noise
- Birdies
- Battery Power
Let’s take a closer look at each of the above issues.
Table des matières
Line of sight
Line of sight means you usually cannot hear stations beyond the horizon, or your line of sight (approximately 30-35 miles away).
Of course this will depend on the surrounding terrain, the type of antenna you are using, and if it is on a repeated or non-repeated system.
Surrounding Terrain
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 on our « Police Scanners & Accessories » page.
Type of Antenna used
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 on our « Police Scanners & Accessories » page.
Repeated or non-repeated stations
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.
Frequency behavior
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.
When it comes to a radio scanner’s ability to receive signals, there are many factors that affect the range (scanners maximum receivable distance) and reception (clarity of the signal received).
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.
| 31.05 00 32.0000 41.4000 51.7500 74.2000 113.8500 124.2000 128.0000 139.9950 140.0000 144.9000 155.2500 167.9950 171.2500 471.9870 483.9250 511.9250 |
The bottom line here is that fully charged or fresh new batteries will give you better range and reception than if you are running on weak ones. Most scanners on the market now include a « Battery Low » indicator to let you know when your batteries are running low. If your scanner does not have this feature, you can usually tell your batteries are getting low because reception starts to break.
