Entry Level Consumer and Amateur (Ham) Radio - Best Bands, Frequencies, Equipment

The objective of this article is to highlight only those frequency bands which permit affordable, practical, and easy operation. The emphasis of this article is only on those bands which are suitable for mobile or hand-held operation, and which will give a usable communication range.

Definition of a band

Thru the speed of light in vacuum, c, there exists a relationship between the frequency of an electromagnetic wave and its wavelength. The easy relationship to remember is that 300MHz is equal to 1m wavelength, with higher frequencies being shorter wavelengths. Therefore, 30MHz will be 10m, while 3GHz will be 10cm wavelengths, respectively.

Propagation Characteristics

The wavelength of the electromagnetic wave affects its behavior. Long wavelengths (100 meters or longer) can follow the curvature of the earth, so that the two antennas can be at different heights or geographical features. This wavelength can also follow topographical features such as mountains and hills, to some extent. At night, this wavelength can also reflect off the ionosphere, bounce down and up off the earth's surface, and travel a long distance.

Medium wavelengths, around 10m, are affected by the ionospheric propagation to a very large extent, since their ability to follow the curvature of the earth are more limited, and this direct route is not very long compared to the long wavelength.

Shorter wavelengths are primarily direct line of sight, and straight, communication paths. The two antennas should be able to "see" each other. Obstructions along this direct path will attenuate (reduce) the signal strength. Obstructions which are smaller that the wavelength will cause the electromagnetic wave to warp around the obstruction to some extent, while obstructions larger than the wavelength will usually cause absorption or reflection.

Modulation

AM, or amplitude modulation, historically was the fist modulation scheme to be developed. A carrier wave, to which the receiver will tune to, is held to be a constant frequency, but the amplitude, or power, of the emitted electromagnetic wave is varied up or down based on the modulating input. The two advantages of AM modulation are 1) the low necessary bandwidth, which necessitates use of AM modulation at lower frequencies, and 2) several stations can be received at the same time by the receiver, which requires use of AM for critical applications such as ground to aircraft communication links. The public is familiar with AM modulation without knowing its meaning, when the 535 kHz to 1705 kHz public broadcast frequency range is referred to as the "AM Band", and labelled so on the radios.

A variety of phenomena in nature can sporadically affect the amplitude of background electromagnetic spectrum, and present itself as unwanted noise at the receiver. This phenomena includes lightning, electric motors, any sparks, including those in the internal combustion engine, fluorescent lighting, and so on.

FM, or frequency modulation, modulates the frequency of the carrier wave up or down. FM requires a much wider bandwidth compared to AM, but since few sources in nature can affect or emit changing signal frequency, the background noise which the receiver receives is much lower. Only one transmitter can be hear over FM - the strongest signal wins the receiver's attention.

Bands

560 to 180 meters

"AM Band" 535 kHz to 1705 kHz

This band is one of two that every commercial radio can receive. The signal follows the curvature of the earth. Commercial AM transmitters at radio stations can have up to 50kW of power, and very tall radio mast antennas are used. During the daylight, reception by the consumer is possible up to 500 miles away. At night, the signal can bounce off the ionosphere and the earth, permitting a much longer range. Commercial AM transmitters lower their output power at night to not interfere with other distant transmissions.

Because the signal which the listener receives can consist of both direct wave (which followed the curvature of the earth), and the one reflected off ionosphere, the two (or more) can either cancel or reinforce each other, resulting in the "loudness" of the reception to vary up or down slowly, sometimes dropping below comprehension.

11 meters

Citizen's Band is located on frequencies from 26.965 to 27.405 MHz. This is commonly referred to as the 11 meters band. This band was very popular in the seventies, with popularity gradually waning. This band is very popular with truckers, who are typically found on channel 19. Channel 9 is the emergency use only channel.

While a large vehicle-mounted antenna allows non-line-of-sight operation, CB has several drawbacks:

1) The long wavelength makes handheld units to require long antennas for good reception, which is not always convenient.

2) Use of a handheld from inside the car is unfeasible (since the

compare to AM, FM bands, cellphone, baby monitors, handheld phone, microwave, wi-fi

fm multipath

fire, police, emt bands

CB handheld unusable in car

mobile station with 12V SLA or lithium batt pack

AM modulation for safety (can hear several people), but electromagnetic noise from many sources

typical power, antenna size, distance

cannot do CB from inside car with a handheld

bands for taxi, police, fire, etc

only covers handheld or mobile related bands and equipment, with usable voice capability

Yaesu, I-Com, Tin-Tac??

CB, 2m, 70cm, FRS, GPRS

EMS, Fire, Police, Taxi bands

amateur general license

ARRL, local club

internet scanners

used equipment. Include links to e-bay, google shopping, custom craigslist search, amazon.

Mobile, car one is better

good antenna more important than fancy equipment

UHF is line-of-sight

Business Band

GMRS - Theoretical range between two hand-held units would be about one or two miles (about one and a half to three km), mobile units have higher antennas and range of around 5 miles (8 km)