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Saturday, September 18, 2010

About Citizens' band radio (Must Read)

Hand-held CB transceiver Citizens' Band radio (often shortened to CB radio) is, in many countries, a system of short-distance radio communications between individuals on a selection of 40 channels within the 27-MHz (11 m) band. The CB radio service is distinct from FRS, GMRS, MURS, or amateur ("ham") radio. In many countries, CB does not require a license and, unlike amateur radio, it may be used for business as well as personal communications. Like many other two-way radio services, Citizens' Band channels are shared by many users. Only one station may transmit at a time. Other stations must listen and wait for the shared channel to be available.
Over time, several countries have created similar radio services, with varying requirements for licensing and differing technical standards. While they may be known by other names, such as General Radio Service in Canada,[1] they often use similar frequencies (26 to 28 MHz), and have similar uses, and similar difficulties with antennas and propagation. Licenses may be required, but eligibility is generally simple.
Some countries have personal radio services in the UHF band, such as the European PMR446 and the Australian UHF CB.

United States
The Citizens' Band radio service originated in the United States as one of several personal radio services regulated by the Federal Communications Commission (FCC). These services began in 1945 to permit citizens a radio band for personal communication (e.g., radio-controlled models, family communications, individual businesses). In 1948, the original "Class D" CB Radios were to be operated on the 460 MHz–470 MHz UHF band .[2] There were two classes of CB: A and B. Class B radios had simpler technical requirements but were limited to a smaller range of frequencies. Al Gross, inventor of the walkie-talkie, started Citizen's Radio Corp. in the late 1940s to merchandise Class B handhelds for the general public.[3]
Ultra-high frequency, or UHF, radios, at the time, were neither practical nor affordable for the average consumer. In 1958,[4] the Class D CB service was moved to 27 MHz, and this band became what is popularly known as CB. There were only 23 channels at the time; the first 22 were taken from what used to be an Amateur 11-meter band, while channel 23 was shared with radio-controlled devices. Some hobbyists continue to use the designation "11 meters" to refer to the Citizens' Band and adjoining frequencies. Section 95 of the Federal Communications Code regulated the Class D CB service, on the 27 MHz band, as of the 1970s.[citation needed]
Most of the 460 MHz–470 MHz band was reassigned for business and public safety uses, but Class A CB is the ancestor of the present General Mobile Radio Service GMRS. Class B, in the same vein, is a more distant ancestor of the Family Radio Service. The Multi-Use Radio Service is another two-way radio service, in the VHF high band. An unsuccessful petition was made in 1973 to create a Class E CB service at 220 MHz, this was opposed by amateur radio organizations[5] and others. There are several other classes of personal radio services for specialized purposes such as remote control devices.
In the 1960s, the service was popular with small trade businesses (e.g., electricians, plumbers, carpenters), as well as truck drivers and radio hobbyists. By the late 60s the advancement of solid-state electronics allowed the weight, size, and cost of the radios to decrease, giving the general public access to a communications medium that had previously been only available to specialists. Many CB clubs were formed, and a special CB slang language evolved, used alongside 10-codes similar to those used in the emergency services.
Growing popularity in the 1970s
Following the 1973 oil crisis, the U.S. government imposed a nationwide 55 mph speed limit, and fuel shortages and rationing were widespread. CB radio was often used, especially by truckers, to locate service stations with a supply of gasoline, to notify other drivers of speed traps, and to organize blockades and convoys in a 1974 strike protesting the new speed limit and other trucking regulations. Throughout the 1970s and early 1980s, a phenomenon was developing over the CB radio. Similar to the Internet chat rooms a quarter century later, the CB allowed people to get to know one another in a quasi-anonymous manner. Many movies and stories about CBers and the culture on-the-air developed.
The prominent use of [6] CB radios in 1970s-era films (see list below) such as Smokey and the Bandit (1977), Convoy (1978), and television shows like Movin' On (debuted 1974) and The Dukes of Hazzard (debuted 1979) bolstered the appeal of CB radio. Moreover, popular novelty songs such as C.W. McCall's Convoy (1976) helped establish CB radio as a nationwide craze in the USA in the mid- to late-1970s.
Originally, CB required a license and fee (it was $20.00 in the early 70's; and $4.00 in the late 70's), and the use of a call sign, but when the CB craze was at its peak, many people ignored this requirement and used made-up nicknames or "handles". The many restrictions on the authorized use of CB radio led to widespread disregard of the regulations, most notably in antenna height, distance restriction for communications, licensing and the use of call signs, and allowable transmitter power. After the FCC started receiving over 1,000,000 license applications a month, the license requirement was dropped entirely.
Originally, there were only 23 CB channels in the U.S.; the present 40-channel bandplan did not come along until 1977. Channel 9 was reserved for emergency use in 1969.[7] Channel 10 was used for highway communications at first, then, it was Channel 10 east of the Mississippi River, and channel 19 west of the Mississippi; then later Channel 19 became the preferred highway channel in most areas, as it did not have adjacent-channel interference problems with channel 9. Many CB'ers called Channel 19 "the trucker's channel".
Until 1975,[8] only channels 9–15 and 23[9] could be used for "interstation" calls to other licensees. Channels 1–8 and 16–22 were reserved for "intrastation" communications among units under the same license.[10] After the interstation/intrastation rule was dropped, Channel 11 was reserved as a calling frequency for the sole purpose of establishing communications; however this was withdrawn in 1977.[11] During this time period, it was common for many CB radios to have these "interstation" channels 'colored' on their dial, whilst the other channels were 'clear' or 'normal'; with the exception of Channel 9 - it was usually colored Red. Also, it was common for Single Sideband (SSB) users to use Channel 16 as 'their' channel.
It was also very common for towns relatively close together, to 'adopt' one of these "interstation" channels as their 'home' channel. This accomplised two things: first, this help prevent overcrowding on Ch 11, and 2nd; this allowed a CB'er to go to that town's 'home channel' to try and contact another CB'er from that town, instead of a general 'call' on Ch 11.
In more recent years, CB has lost much of its original appeal due to development of mobile phones, the Internet, and Family Radio Service. The changing radio wave propagation for long-distance communications, due to the 11 year sunspot cycle, is always a factor for these frequencies. In addition, CB in some respects became a victim of its own intense popularity. Because of the millions of users jammed onto frequencies during the mid-to-late 1970s and early 1980s, channels often were intolerably noisy and communication became difficult. Many CBers started to use their radios less frequently or not at all after this period.
Before CB was authorized in Australia, there were hand held 27 MHz "walkie-talkies" that utilised several frequencies in between the present CB channels, such as 27.240 MHz.[12][13] By the mid-1970s, hobbyists were experimenting with these handheld radios, as well as with unauthorized American CB radios. At that time in Australia, the 11-meter band was still used by licenced ham operators[14] but not yet available for CB-type use.
A number of CB clubs had formed by this time, which assigned callsigns to members, exchanged QSL cards, and lobbied for the legalization of CB. In 1977, CB was legalized with an 18-channel bandplan.[15] Later, in 1980, the American 40-channel bandplan was adopted. From the outset, the Government attempted to regulate CB radio with licence fees and call-signs etc, but some years later abandoned this approach.
The first CB club in Australia was the Charlie Brown Touring Car Club (CBTCC)[citation needed], which formed in Morwell, Victoria in 1967 and consisted of members who were mainly four-wheel drive enthusiasts. The club used the prefix GL (for Gippsland) due to the fact that "CB" could not be used. After July 1, 1977, the club changed its name to Citizens Band Two Way Communication Club (CBTCC).[citation needed] Other early clubs were the LV (Latrobe Valley) and the WB named after Wayne Britain. Members of these clubs are still about and have also become amateur radio operators.
With the introduction of UHF CB radios in 1977, many operators used both UHF and HF radios and formed groups to own and operate local FM repeaters.
Members of the CBTCC formed what became known as Australian Citizens Radio Movement (ACRM) in the early 1970s and this organisation became the mouthpiece for CB radio legalisation throughout Australia.
After peaking in the 1970s and early 1980s, the use of 27 MHz CB in Australia has fallen dramatically in the last decade. The later introduction of 477 MHz UHF CB, with FM and repeaters, and the proliferation of cheap, compact handheld UHF transceivers have been part of the reason. Technologies such as mobile telephones and the Internet have provided people with other choices for communications.
The Australian Government is currently working on changing the allocation of channels available for UHF CB Radio from 40 to 80 as well as doubling the number of repeater channels from 8 to 16.[16]
In Canada, the "General Radio Service" has the identical frequencies and modes as the United States "Citizen's band", and no special provisions are required for either Canadians or Americans using CB gear while traveling across the border.
The General Radio Service was authorized in 1962. Initially CB channels 1 through 3 remained allocated to amateur radio and channel 23 was used by paging services. American CB licensees were initially required to apply for a temporary license to operate in Canada.[17] In April 1977 the service was expanded to the same 40 channels as the American service.[18]
In Indonesia, CB radios were first introduced around 1977 when some transceivers were imported illegally from Australia, Japan and the United States. The dates are hard to confirm accurately but certainly early use was known around big cities such as Jakarta, Bandung, Yogyakarta, Surabaya and Medan.
The Indonesian government legalized CB on October 6, 1980 through a decision of the Minister of Communications called the Ministerial Decree on the Licensing for the Operation of Inter-Citizens Radio Communication. Because many people were already using 40-channel radios prior to legalization, the American bandplan, with AM and SSB, was adopted; a VHF band was added later in 1994. On November 10, 1980, the Indonesian Directorate General of Posts and Telecommunications issued another decree establishing RAPI (Radio Antar Penduduk Indonesia) as the official citizens band radio organization in Indonesia.[19]
In Malaysia, Citizen's Band radios became legal when Notification of Issuance Of Class Assigments by Communication and Multimedia Malaysia was gazzeted on 1 April 2000. In this class assignment, CB radio is called "Personal Radio Service Device". The frequency band is HF, 26.9650MHZ to 27.4050MHZ (40 CH), power output is 4 watt for AM/FM and 12 watt pep for SSB. CH 9 reserved for emergency and CH 11 is a calling channel. On UHF 477 MHZ, Citizen Band PRS radio devices are allowed 5 watts power output and use FM modulation, on 39 assigned channels spaced at 12.5 kHz between 477.0125 MHZ to 477.4875 MHZ. Channel 9 is reserved for emergency and Channel 11 for calling. A very short-range simplex radiocommunications service for recreational use is on 477.5250MHZ to 477.9875MHZ on FM mode with 38 channels and power output of 500mw. CB (citizen band) radio or Personal Radio Service Device under Class Assignment do not need an individual license to operated in Malaysia as long as follows to the rules of Warta Kerajaan Malaysia , Communication and Multimedia act 1998[Act 588], Notification of Issuance Of Class Assignment, P.U.(B)416 Jil. 48,no. 22 (e)Personal Radio Service Device 1November 2004. [20]
On 1 April 2010 MCMC (Malaysian Communications and Multimedia Commission) release a new Notification of issuance of Class Assignment called Communications and Multimedia Act 1998 Class Assigments No. 1 of 2010 that include a new UHF PMR 446 MHZ, 8 Channel for Analog Personal Mobile Radio 446 MHZ (Analog PMR446), frequency from 446.0025 Mhz to 446.09375 Mhz (12.5Khz spacing) on FM mode 0.5Watt power output and 16 Channel for Digital Personal Mobile Radio 446 Mhz (Digital PMR 446). Frequency for Digital PMR 446 is from 446.103125 Mhz to 446.196875 Mhz on 6.25 Khz spacing on 4FSK mode and power out 0.5 Watt.[21]
One of unofficial citizen band radio club in Malaysia is "Malaysia Boleh Citizen Radio Group" or what we called is MIKE BRAVO which mean Malaysia Boleh.[22]
United Kingdom
In Great Britain, some people were illegally using American CB radios in the 1970s. The prominence of CB radio grew in Britain partly due to the popularity of novelty songs like CW McCall's "Convoy" and Laurie Lingo & The Dipsticks' "Convoy GB" in 1976 (both of which were Top 5 hits), and then the film Convoy in 1978. By 1980, CB radio had become a popular pastime in Britain, however, as late as the summer of 1981, the British government was still saying that CB would never be legalized on 27 MHz, and proposed a UHF service around 860 MHz called "Open Channel" instead.
However, in November 1981, and after high profile public demonstrations, 40 frequencies unique to the UK, known as the 27/81 Bandplan, and using FM, were allocated at 27 MHz, plus 20 channels on 934 MHz (934.0125 to 934.9625 MHz with 50-kHz-spacing). CB's inventor Al Gross made the ceremonial first legal British CB call from Trafalgar Square, London. The maximum power allowable on 27/81 was 4 watts, in common with the American system, although initially the set had to be equipped with a facility to reduce the output to a mere 0.4 watts if the antenna was mounted more than 7 metres above ground level. That rule was relaxed fairly quickly, although the power reduction switch could still prove useful in cases of TV interference.
Later, the UK added the more usual 40 frequencies used worldwide for a total of 80 channels at 27 MHz, and the 934 MHz band was withdrawn in 1998.
CB radio in the UK was deregulated in December 2006 by the regulatory body Ofcom, and CB radio in the UK is now license-free. The old 27/81 band will not be withdrawn from service in the near future and will continue to be available for the foreseeable future.
The rules regarding non-approved radios, modes other than FM, and power levels above 4 watts still apply, regardless of the deregulation. Anyone using illegal equipment or accessories is still running the risk of prosecution, fines, and/or confiscation of equipment.
Although the use of CB radios in the UK is limited, it is still popular, especially with the farming community and Mini-Cab services. The widely accepted channel for the Young Farmers Club is Channel 11.
CB frequencies worldwide
Similar radio services exist in many countries around the world. Frequencies, power levels, and modes (such as FM, AM and SSB) may vary from country to country, and usage of foreign equipment may be illegal. However, many countries have adopted the American frequencies.
In Europe, the CEPT adopted the North American channel assignments, except that FM is used instead of AM. Some member countries permit additional modes and frequencies. Germany also has 40 unique channels at 26 MHz for a total of 80. Before CEPT, most of the member countries used some subset of the 40 USA channels.
In Poland (and probably some other former Warsaw Pact countries) the channels are shifted 5 kHz down, so for example channel 30 is 27.300 MHz, many operators add a switch that can change between the "zeroes" (the Polish channel assignment), and the "fives" (the international assignment).
New Zealand and Japan have unique allocations that do not correspond to any other country.
Indonesia has the usual 40 channels at 27 MHz, plus a unique 60-channel allocation from 142.050 MHz–143.525 MHz.[23]
Using radios outside their intended market can be dangerous as well as illegal.
CB Radio today
CB was once the only practical two-way radio system for the individual consumer, and as such served several distinct types of users such as truck drivers, radio hobbyists, and those who needed a short-range radio for particular tasks. While some of these users have moved on to other radio services, CB is still a popular hobby in many countries. In the United States it is strongly associated with semi truck drivers and rural life.
The 27-MHz-frequencies used by CB, which require a long aerial antenna and tend to propagate poorly indoors, tend to discourage use of handheld radios. Many consumer users of handheld radios (e.g. family use, hunters, hikers) have moved on to 49 MHz and then to the UHF Family Radio Service, while many who need a simple radio for professional use (e.g. tradesmen) have moved on to "dot-color" business radios.
On the other hand, CB is still popular among long-haul truck drivers to communicate directions, traffic problems, and other things of importance.[25] Truckers are known to tune to the unofficial "travelers channel," which is channel 19 (Australia it is channel 40). This has long been the case in the United States, but less so in Europe where until recently conflicting regulations made it impossible for the same radio to be used across Europe. As a result, CB in Europe became more associated with hobbyists than with truckers.
Legitimate, short-range use of CB radio is sometimes made difficult by users of illegal high-power transmitters, which are capable of being heard hundreds of miles away. In the United States, the vast number of users and the low financing of the regulatory body mean that the regulations are only actively enforced against the most severe interfering stations, which makes legitimate operations on the Citizen's band unreliable.
The maximum legal CB power output level in the U.S. is four watts for AM and 12 watts (peak envelope power or "PEP") for SSB, as measured at the antenna connection on the back of the radio. However, illegal external linear amplifiers are frequently used. In the 1970s the FCC banned the sale of linear amplifiers capable of operation from 24 to 35 MHz to discourage their use on the CB band, though the use of high power amplifiers by lawless pirate operators continued. Late in 2006 the FCC amended the regulation to only exclude 26 to 28 MHz.[26] Extremely lax enforcement of these regulations by the FCC has led to manufacturers of illegal linear amplifiers openly advertising their products for sale, and many CB dealers carry these and other amplifiers in their product lines and include them in catalogs.
At the introduction of the CB radio service, transmitters and receivers necessarily used vacuum tubes. All solid-state transmitters were not widely available until 1965, after introduction of suitable RF power transistors.[27] Walkie-talkie hand-held units were made affordable by the use of transistors. Early receivers did not implement all channels of the service; channels were controlled by plug-in quartz crystals, with one of several operating frequencies selected by a panel control in more expensive units. Superheterodyne receivers, using one or two conversion stages, were usual in good quality equipment, although extremely low cost toy units occasionally used superregenerative receivers. With the earliest sets, two quartz crystals were needed for transmitting and receiving on each channel. This was costly. By the mid-1960s, "mixer" circuits made frequency synthesizer radios possible, which reduced cost and allowed full coverage of all 23 channels with a smaller number of crystals, typically 14. The next evolution was in the mid 1970s, where the method of crystal synthesis was replaced by PLL technology using ICs, enabling 40 channel sets to be achieved ultimately using only one crystal (10.240 mhz). Almost all were AM only, though there were a few single sideband sets.
Most CB radios sold in the United States today come with the following features:
  • ANL/NB – automatic noise limiter or noise blanker reduces background noise, such as spark ignition noise.
  • CB/WX – selects weather radio receiver.
  • Dynamic or mic gain – AGC adjusts transmitted sound level (modulation level).
  • PA – some CB transceivers can drive an external speaker as a low-power public address system or "bullhorn".
  • RF gain – adjusts the RF amplifier gain of the receiver. It would be used to reduce received background noise and to reduce clipping due to overamplification of already strong signals (for example when the receiver is close to the transmitter).
  • NOR/9/19 – quickly tunes pre-set channels for calling or emergency channels.
  • SWR – a meter used to monitor the reflected power caused by mismatched antennas and antenna cables.
  • Volume – speaker volume control.
Popular microphone choices include:
  • Dynamic – A dynamic microphone uses a magnetic coil and permanent magnet.
  • Ceramic – uses a piezoelectric element; rugged, low cost, but high impedance.
  • Echo – These microphones deliberately introduce distortion and echo into the transmitted audio.
  • Electret – An electret microphone uses an electrostatic method to convert sound to electrical signals.
  • Noise-canceling microphone- uses two elements to reduce background noise.
  • Power mic – An amplified mic.[28]
Shooting skip
All frequencies in the HF spectrum (3–30 MHz) can be refracted by charged ions in the ionosphere. Refracting signals off the ionosphere is called skywave propagation; the operator is said to be "shooting skip". CB operators have communicated across thousands of miles, sometimes around the world, making initial contact on the internationally recognized calling frequency (27.555 MHz), then moving to another frequency. Even low-powered 27 MHz transmitters can sometimes transmit over long distances.
The ability of the ionosphere to bounce signals back to earth is caused by radiation from the sun. The amount of ionization possible is related to the 11-year sunspot cycle. In times of high sunspot activity, the band can remain open to much of the world for long periods of time. During low sunspot activity, it might not be possible to shoot skip at all except during periods of sporadic electron propagation, which occur from late spring through mid-summer. Skip contributes to noise on CB frequencies.
In the United States, it is illegal to engage in, or attempt to engage in, CB communications with any station more than 250 km (150 miles) from an operator's location.[29] This restriction exists to keep CB as a local radio service. The legality of shooting skip is not an issue in most other countries.[30]
Freebanding and export radios
Operation on frequencies above or below the citizen's band (on the "uppers" and "lowers") is called "freebanding" or "outbanding".[31] While frequencies just below the CB band, or between the CB band and the amateur radio 10-meter band seem quiet and under-utilized, they are allocated to other radio services, including government agencies, and unauthorized operation on them is illegal. Furthermore, illegal transmitters and amplifiers may not meet good engineering practice for harmonic distortion or "splatter", which may disrupt other communications and make the unapproved equipment obvious to regulators.
Freebanding is done sometimes with modified CB equipment, mostly with amateur radios modified to transmit on 11 meters, foreign CB radios that may offer different channels, or with radios intended for export. This type of radio activity although wide spread throughout the world is in fact illegal in quite a few countries, the UK being one such country where only 80 FM channels are legal.
Unlike amateur radios with continuous frequency tuning, export CBs are channelized. Frequency selection resembles that of modified American CBs more than any foreign frequency plan. They typically have a knob and display that reads up to channel 40, but include an extra band selector that shifts all 40 channels above or below the band, plus a "+10 kHz" button to reach the model control 'A' channels. These radios may have 6 or even 12 bands, establishing a set of quasi-CB channels on many unauthorized frequencies. The bands are typically lettered A through F, with the normal CB band as D.
For example, a freebander with an export radio who wants to use 27.635 MHz would choose Channel 19 (27.185 MHz) and then shift the radio up one band (+ 0.450 MHz). It requires arithmetic on the part of the operator to determine the actual frequency, though more expensive radios include a frequency counter or a frequency display, bear in mind and frequency counter and a frequency display are in fact two different things which give the same final out come.
Even well-meaning, but illegal, operations can end up on frequencies which are very much in use. For instance, Channel 19, shifted two bands up, becomes 28.085 MHz, which is in a Morse code-only part of the 10-meter ham band. Licensed amateurs typically regard this activity as an intrusion, and have been known to record, locate, and report such transmissions.[32]
Currently, many freeband operators use amateur radios modified to transmit out of band which again in some countries use of amateur radios modified to operate outside their required bands is illegal. Older amateur radios may require component changes; for instance, the 1970s-vintage Yaesu FT-101 was modified for CB by replacing a set of crystals used to tune portions of the 10-meter band, although some variants of the FT-101 did come with the US FCC channels standard, and were capable of transmitting above and below the legal 40 channels by another 10 or more channels.[33] while on some newer radios, the modification may be as simple as cutting a jumper or diode. Today many types of amateur radios can be found on CB and freeband, ranging from full-coverage HF transceivers to simpler 10-meter mobile radios. In the United States, the FCC bans the importation and marketing of radios it deems too easily modifiable for the CB frequencies,[34] and it is illegal to transmit on CB frequencies with a ham radio except in emergencies where no other method of communication is available.
A gray market trade in imported CB gear does exist in many countries. In many instances, sale or ownership of foreign-specification CB gear is not illegal, but the actual use of it is. With the FCC's minimal enforcement of its rules regarding CB radio, enthusiasts in the USA often use "export" radios, or possibly European FM CB gear to get away from the overcrowded AM channels. American AM gear has also been exported to Europe.
"Export" radios are marketed in the United States as 10 Meter Amateur transceivers. The marketing, importing and sale of such radios is illegal, if the radios are marketed as anything other than Amateur transceivers. It is also illegal to use these radios outside of the amateur radio bands by anyone in the USA as these radios are not type certified for the other radio services and usually exceed power limits. The use of these radios within the amateur radio service by a licensed amateur radio operator within his/her privileges is legal as long as all amateur rules are followed.
Please also bear in mind such radios that are 11mtr capable are illegal for use in the UK, even though legally sold on auction sites and by retailers, they are illegal to use as these do not cover any of the type approved systems for the UK. The UK 80 legal CB channels, these being the 'mid' band which is 26.965 to 27.405 in FM mode, and the older UK channels 27.60125 to 27.99125 again in FM mode, any other modes (AM and SSB) are illegal and any such radio being used that covers more channels or modes other than the approved channels are illegal for use. There is also no CB licence required in the UK, however the rules still apply to the radios and must still be observed. The UK radio authority 'OfCom' will take action against illegal operations.
CB antennas
Typical center-loaded mobile CB antenna. Note the size of the loading coil, which is typical of higher transmit power capability.
As 27 MHz is a relatively long wavelength for mobile communications, and as with all radio systems, the choice of antenna has a considerable impact on the performance of a CB radio.
One common mobile antenna is a quarter-wave vertical whip. This is roughly nine feet (2.7 m) tall and mounted low on the vehicle body, and often has a spring and ball mount to enhance its resilience to scraping and striking overhead objects.
Where a nine-foot whip would be impractical, shorter antennas include loading coils to make the antenna electrically longer than it actually is. The loading coil may be on the bottom, middle, or top of the antenna, while some antennas are wound in a continuously loaded helix.
Many truckers use two co-phased antennas mounted on their mirrors. Such an array is intended to enhance performance to the front and back, while reducing it to the sides, a desirable pattern for long-haul truckers. However, the efficiency of such an arrangement is only an improvement over a single antenna when the co-phased antennas are separated by approximately eight feet or more, restricting this design to use mainly on tractor trailers and some full-size pickups and SUVs. Some operators will use only one of the antennas in the pair; this removes both the complexity and benefit of a true co-phased array but gives a symmetrical cosmetic appearance that some truck drivers prefer.
Another mobile antenna is the continuously-loaded half-wave antenna. These do not necessarily require a ground plane to present a near 50 Ohm load to the radio, and are often used on fiberglass vehicles such as snowmobiles or boats. They are also ideal for base station usage where the circumstances preclude the use of an antenna that requires a ground plane to function properly.
Handheld CBs often use either a telescoping center-loaded whip, or a continuously-loaded “rubber ducky” antenna.
Base CB antennas may be vertical for omnidirectional coverage, or directional "beam" antennas may be used to direct communications to a particular region. "Ground Plane" kits exist as a mounting base for typical mobile whips, and have several wire terminals or hardwired ground radials attached. These kits are designed to have a mobile whip screwed on top (again, the full-length steel whip is a preferred candidate) and mounted on top of a mast. The ground radials take the place of the vehicle body, which is used as a counterpoise for the mobile whip in a typical vehicle installation.


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