Archive for the ‘Ham Radio’ Category

Amateur radio VHF/UHF repeaters.

Article by Carl Broady

Most new amateur radio operators start out on the VHF and UHF amateur radio bands.

Upon obtaining an amateur radio license or "ticket" most amateurs first investment is in a dual band hand held two way radio, usually referred to as an HT or Handy talkie, a term which evolved from the old term: walkie-talkie. Usually the amateur radio operators second investment is in a mobile dual band UHF/VHF transceiver which they install in their vehicle or Radio Shack. These two radios have very similar functionality but the handheld battery-operated unit is usually limited to a maximum output power of about five watts. The mobile radio which is connected to the vehicles 12 Volt power supply, or if it used as a base station, to a transformer supplying 12 Volts DC and is capable of transmitting usually up to about 35 watts.

VHF and UHF communication is line of sight. Depending on the power output and the location of the transmission antenna VHF and UHF signals are capable of reaching the visible horizon and maybe just a little bit beyond, but that is the limit. There is one notable exception to this rule which is Tropospheric ducting where under very unusual and quite rare weather conditions VHF and UHF radio signals travel very much further than the horizon. Amateur radio operators take advantage of this phenomena when it does occur by communicating with other amateurs over great distances.

A 5 Watt handy talky will have an effective range depending on the terrain and elevation of about 3 miles. A mobile radio on full power will probably have a maximum range of 15 to 20 miles under ideal conditions. To overcome this limitation in range amateur radio operators utilize radio repeaters, which are usually owned and operated by amateur radio clubs, but some are privately owned. These repeaters listen or receive on one frequency and transmit on a different frequency, this is usually referred to as "the split". The repeater takes the signal that it receives on the input frequency and instantaneously retransmits it on the output frequency using a lot more power usually about 100 W. In addition to the higher power most of these radio repeaters antennas are located on the top of very high buildings or towers which really increases the range.

An amateur with an HT can transmit on the repeater's input frequency and receive on the repeater's output frequency effectively increasing the range of the handheld radio to just beyond the horizon maybe even 30 or 40 miles away. Many repeater systems have one main transmitter but may have several receiving antennas located throughout the repeater's coverage area. In this way a large city can be completely covered with a repeater system with hams being able to receive the repeater just about anywhere in the city and they are able to be received by the repeater or "hit the repeater" as it is usually referred to, again from just about anywhere in the city.

In recent times radio repeaters around the world have been connected to the Internet and can be linked to each other via the Internet. For example an amateur radio operator in Sydney Australia with an HT can chat with a fellow amateur who is driving in their car in New York city USA. Some repeater systems are continually linked to each other but most are linked as and when required by the user and the link is dropped at the end of the conversation.

Most amateur repeaters are open to all licensed amateur radio operators free of charge. These repeaters do cost money to buy, operate and maintain. They are usually funded by club membership dues. If an amateur finds themselves using a repeater frequently then maybe they should really consider joining the club that owns the repeater and help to fund it.

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Radio propagation

Free space propagation

In free space, all electromagnetic waves (radio, light, X-rays, etc) obey the inverse-square law which states that the power density of an electromagnetic wave is proportional to the inverse of the square of the distance from the source or:

Doubling the distance from a transmitter means that the power density of the radiated wave at that new location is reduced to one-quarter of its previous value.

The power density per surface unit is proportional to the product of the electric and magnetic field strengths. Thus, doubling the propagation path distance from the transmitter reduces each of their received field strengths over a free-space path by one-half.

Modes

Radio frequencies and their primary mode of propagation

Band

Frequency

Wavelength

Propagation via

VLF

Very Low Frequency

330 kHz

10010 km

Guided between the earth and the ionosphere.

LF

Low Frequency

30300 kHz

101 km

Guided between the earth and the D layer of the ionosphere.

Surface waves.

MF

Medium Frequency

3003000 kHz

1000100 m

Surface waves.

E, F layer ionospheric refraction at night, when D layer absorption weakens.

HF

High Frequency (Short Wave)

330 MHz

10010 m

E layer ionospheric refraction.

F1, F2 layer ionospheric refraction.

VHF

Very High Frequency

30300 MHz

101 m

Infrequent E ionospheric refraction. Extremely rare F1,F2 layer ionospheric refraction during high sunspot activity up to 80 MHz. Generally direct wave. Sometimes tropospheric ducting.

UHF

Ultra High Frequency

3003000 MHz

10010 cm

Direct wave. Sometimes tropospheric ducting.

SHF

Super High Frequency

330 GHz

101 cm

Direct wave.

EHF

Extremely High Frequency

30300 GHz

101 mm

Direct wave limited by absorption.

Surface modes

Main article: Surface wave

Lower frequencies (between 30 and 3,000 kHz) have the property of following the curvature of the earth via groundwave propagation in the majority of occurrences.

In this mode the radio wave propagates by interacting with the semi-conductive surface of the earth. The wave "clings" to the surface and thus follows the curvature of the earth. Vertical polarization is used to alleviate short circuiting the electric field through the conductivity of the ground. Since the ground is not a perfect electrical conductor, ground waves are attenuated rapidly as they follow the earth surface. Attenuation is proportional to the frequency making this mode mainly useful for LF and VLF frequencies.

Today LF and VLF are mostly used for time signals, and for military communications, especially with ships and submarines. Early commercial and professional radio services relied exclusively on long wave, low frequencies and ground-wave propagation. To prevent interference with these services, amateur and experimental transmitters were restricted to the higher (HF) frequencies, felt to be useless since their ground-wave range was limited. Upon discovery of the other propagation modes possible at medium wave and short wave frequencies, the advantages of HF for commercial and military purposes became apparent. Amateur experimentation was then confined only to authorized frequency segments in the range.

Direct modes (line-of-sight)

Line-of-sight is the direct propagation of radio waves between antennas that are visible to each other. This is probably the most common of the radio propagation modes at VHF and higher frequencies. Because radio signals can travel through many non-metallic objects, radio can be picked up through walls. This is still line-of-sight propagation. Examples would include propagation between a satellite and a ground antenna or reception of television signals from a local TV transmitter.

Ground plane reflection effects are an important factor in VHF line of sight propagation. The interference between the direct beam line-of-sight and the ground reflected beam often leads to an effective inverse-fourth-power law for ground-plane limited radiation. [Need reference to inverse-fourth-power law + ground plane. Drawings may clarify]

Ionospheric modes (skywave)

Main article: Skywave

Skywave propagation, also referred to as skip, is any of the modes that rely on refraction of radio waves in the ionosphere, which is made up of one or more ionized layers in the upper atmosphere. F2-layer is the most important ionospheric layer for HF propagation, though F1, E, and D-layers also play some role. These layers are directly affected by the sun on a daily cycle, the seasons and the 11-year sunspot cycle determines the utility of these modes. During solar maxima, the whole HF range up to 30 MHz can be used and F2 propagation up to 50 MHz are observed frequently depending upon daily solar flux values. During solar minima, propagation of higher frequencies is generally worse.

Forecasting of skywave modes is of considerable interest to amateur radio operators and commercial marine and aircraft communications, and also to shortwave broadcasters.

Meteor scattering

Meteor scattering relies on reflecting radio waves off the intensely ionized columns of air generated by meteors. While this mode is very short duration, often only from a fraction of second to couple of seconds per event, digital Meteor burst communications allows remote stations to communicate to a station that may be hundreds of miles up to over 1,000 miles (1,600 km) away, without the expense required for a satellite link. This mode is most generally useful on VHF frequencies between 30 and 250 MHz.

Auroral reflection

Intense columns of Auroral ionization at 100 km altitudes within the auroral oval reflect radio waves, perhaps most notably on HF and VHF. The reflection is angle-sensitive - incident ray vs. magnetic field line of the column must be very close to right-angle. Random motions of electrons spiraling around the field lines create a Doppler-spread that broadens the spectra of the emission to more or less noise-likeepending on how high radio frequency is used. The radio-auroras are observed mostly at high latitudes and rarely extend down to middle latitudes. The occurrence of radio-auroras depends on solar activity (flares, coronal holes, CMEs) and annually the events are more numerous during solar cycle maximas. Radio aurora includes the so-called afternoon radio aurora which produces stronger but more distorted signals and after the Harang-minima, the late-night radio aurora (sub-storming phase) returns with variable signal strength and lesser doppler spread. The propagation range for this predominantly back-scatter mode extends up to about 2000 km in east-west plane, but strongest signals are observed most frequently from north at nearby sites on same latitudes.

Rarely, a strong radio-aurora is followed by Auroral-E, which resembles both propagation types in some ways.

Sporadic-E propagation

Sporadic E (Es) propagation can be observed on HF and VHF bands. It must not be confused with ordinary HF E-layer propagation. Sporadic-E at mid-latitudes occurs mostly during summer season, from May to August in the northern hemisphere and from November to February in the southern hemisphere. There is no single cause for this mysterious propagation mode. The reflection takes place in a thin sheet of ionisation around 90 km height. The ionisation patches drift westwards at speeds of few hundred km per hour. There is a weak periodicity noted during the season and typically Es is observed on 1 to 3 successive days and remains absent for a few days to reoccur again. Es do not occur during small hours; the events usually begin at dawn, and there is a peak in the afternoon and a second peak in the evening. Es propagation is usually gone by local midnight.

Maximum observed frequency (MOF) for Es is found to be lurking around 30 MHz on most days during the summer season, but sometimes MOF may shoot up to 100 MHz or even more in ten minutes to decline slowly during the next few hours. The peak-phase includes oscillation of MOF with periodicity of approximately 5...10 minutes. The propagation range for Es single-hop is typically 1000 to 2000 km, but with multi-hop, double range is observed. The signals are very strong but also with slow deep fading.

Thomas F. Giella, retired meteorologist, space plasma physicist and an Amateur Radio Operator (NZ4O), cites the following from his professional research:[citation needed][original research?]

Just as the E layer is the main refraction medium for medium frequency (3003000 kHz) signal propagation within approximately 5000 km (3000 mi), so is a Sporadic-E (Es) cloud. Sporadic-E (Es) clouds occur at approximately 100 km (60 mi) in altitude and generally move from ESE to WNW. Like Stratosphere level warming and Troposphere level temperature and moisture discontinuities, Sporadic-E (Es) clouds can depending on the circumstances absorb, block or refract medium, high and very high frequency RF signals in an unpredictable manner.

The main source for "high latitude" Sporadic E (Es) clouds is geomagnetic storming induced radio aurora activity.

The main source for "mid latitude" Sporadic-E (Es) clouds is wind shear produced by internal buoyancy/gravity waves (IBGW's), that create traveling ionosphere disturbances (TID's), most of which are produced by severe thunderstorm cell complexes with overshooting tops that penetrate into the Stratosphere. Another tie in between Sporadic-E (Es) and a severe thunderstorm is the Elve.

The main sources for "low latitude" Sporadic-E (Es) clouds is wind shear produced by internal buoyancy/gravity waves (IBGW's), that create traveling ionosphere disturbances, most of which are produced by severe thunderstorm cell complexes tied to tropical cyclones. High electron content in the Equatorial Ring Current also plays a role.

The forecasting of Sporadic-E (Es) clouds has long been considered to be impossible. However it is possible to identify certain troposphere level meteorological conditions that can lead to the formation of Sporadic E (Es) clouds. One is as mentioned above the severe thunderstorm cell complex.

Sporadic-E (Es) clouds have been observed to initially occur within approximately 150 km (90 mi) to the right of a severe thunderstorm cell complex in the northern hemisphere, with the opposite being observed in the southern hemisphere. To complicate matters is the fact that Sporadic-E (Es) clouds that initially form to the right of a severe thunderstorm complex in the northern hemisphere, then move from ESE-WNW and end up to the left of the severe thunderstorm complex in the northern hemisphere. So one has to look for Sporadic-E (Es) clouds on either side of a severe thunderstorm cell complex. Things get even more complicated when two severe thunderstorm cell complexes exist approximately 10002000 miles apart.

Not all thunderstorm cell complexes reach severe levels and not all severe thunderstorm cell complexes produce Sporadic-E (Es). This is where knowledge in tropospheric physics and weather analyses/forecasting is necessary.

Some of the key elements in identifying which severe thunderstorm cell complexes have the potential to produce Sporadic-E (Es) via wind shear, from internal buoyancy/gravity waves, that produce traveling ionosphere disturbances include:

1.) Negative tilted mid and upper level long wave troughs.

2.) Approximate 150 knot (170 mph, 280 km/h) jet stream jet maxes that produce divergence and therefore create a sucking vacuum effect above thunderstorm cells, that assist thunderstorm cells in reaching and penetrating the tropopause into the stratosphere.

3.) 500 mb (50 kPa) temperatures of 20 C or colder, which produce numerous positive and negative lightning bolts and inter-related Sprites and Elves.

4.) Approximate 150175 knot (170200 mph) updrafts within thunderstorm cells complexes that create overshooting tops that penetrate the Tropopause into the Stratosphere (See definition #20 on Stratospheric Warming), launching upwardly propagating internal buoyancy/gravity waves, which create traveling ionosphere disturbances and then wind shear.

Tropospheric modes

Tropospheric scattering

At VHF and higher frequencies, small variation (turbulence) in the density of the atmosphere at a height of around 6 miles (10 km) can scatter some of the normally line-of-sight beam of radio frequency energy back toward the ground, allowing over-the-horizon communication between stations as far as 500 miles (800 km) apart. The military developed the White Alice communications system covering all of Alaska, using this tropospheric scattering principle.

Tropospheric ducting

Sudden changes in the atmosphere's vertical moisture content and temperature profiles can on random occasions make microwave and UHF & VHF signals propagate hundreds of kilometers up to about 2,000 kilometers (1,300 mi)nd for ducting mode even farthereyond the normal radio-horizon. The inversion layer is mostly observed over high pressure regions, but there are several tropospheric weather conditions which create these randomly occurring propagation modes. Inversion layer's altitude for non-ducting is typically found between 100 meters (300 ft) to about 1 kilometer (3,000 ft) and for ducting about 500 meters to 3 kilometers (1,600 to 10,000 ft), and the duration of the events are typically from several hours up to several days. Higher frequencies experience the most dramatic increase of signal strengths, while on low-VHF and HF the effect is negligible. Propagation path attenuation may be below free-space loss. Some of the lesser inversion types related to warm ground and cooler air moisture content occur regularly at certain times of the year and time of day. A typical example could be the late summer, early morning tropospheric enhancements that bring in signals from distances up to few hundred kilometers for a couple of hours, until undone by the Sun's warming effect.

Tropospheric delay

This is a source of error in radio ranging techniques, such as in GPS.

Rain scattering

Rain scattering is purely a microwave propagation mode and is best observed around 10 GHz, but extends down to a few gigahertzhe limit being the size of the scattering particle size vs. wavelength. This mode scatters signals mostly forwards and backwards when using horizontal polarization and side-scattering with vertical polarization. Forward-scattering typically yields propagation ranges of 800 km. Scattering from snowflakes and ice pellets also occurs, but scattering from ice without watery surface is less effective. The most common application for this phenomenon is microwave rain radar, but rain scatter propagation can be a nuisance causing unwanted signals to intermittently propagate where they are not anticipated or desired. Similar reflections may also occur from insects though at lower altitudes and shorter range. Rain also causes attenuation of point-to-point and satellite microwave links. Attenuation values up to 30 dB have been observed on 30 GHz during heavy tropical rain.

Aeroplane scattering

Aeroplane scattering (or most often reflection) is observed on VHF through microwaves and besides back-scattering, yields momentary propagation up to 500 km even in a mountain-type terrain. The most common back-scatter application is air-traffic radar and bistatic forward-scatter guided-missile and aeroplane detecting trip-wire radar and the US space radar.

Lightning scattering

Lightning scattering has sometimes been observed on VHF and UHF over distance of about 500 km. The hot lightning channel scatters radiowaves for a fraction of a second. The RF noise burst from the lightning makes the initial part of the open channel unusable and the ionisation disappears soon because of combination at low altitude high atmospheric pressure. Although the hot lightning channel is briefly observable with microwave radar, this mode has no practical use for communications.

Other effects

Diffraction

Knife-Edge diffraction is the propagation mode where radio waves are bent around sharp edges. For example, this mode is used to send radio signals over a mountain range when a line-of-sight path is not available. However, the angle cannot be too sharp or the signal will not diffract. The diffraction mode requires increased signal strength, so higher power or better antennas will be needed than for an equivalent line-of-sight path.

Diffraction depends on the relationship between the wavelength and the size of the obstacle. In other words, the size of the obstacle in wavelengths. Lower frequencies diffract around large smooth obstacles such as hills more easily. For example, in many cases where VHF (or higher frequency) communication is not possible due to shadowing by a hill, one finds that it is still possible to communicate using the upper part of the HF band where the surface wave is of little use.

Diffraction phenomena by small obstacles are also important at high frequencies. Signals for urban cellular telephony tend to be dominated by ground-plane effects as they travel over the rooftops of the urban environment. They then diffract over roof edges into the street, where multipath propagation, absorption and diffraction phenomena dominate.

Absorption

Low-frequency radio waves travel easily through brick and stone and VLF even penetrates sea-water. As the frequency rises, absorption effects become more important. At microwave or higher frequencies, absorption by molecular resonance in the atmosphere (mostly water, H2O and oxygen, O2) is a major factor in radio propagation. For example, in the 5860 GHz band, there is a major absorption peak which makes this band useless for long-distance use. This phenomenon was first discovered during radar research during World War II. Beyond around 400 GHz, the Earth's atmosphere blocks some segments of spectra while still passes somehis is true up to UV light, which is blocked by ozone, but visible light and some of the NIR is transmitted.

Heavy rain and snow also affect microwave reception.

See also

Radio portal

Main article: List of radio propagation terms

Diversity scheme

Earth bulge

Electromagnetic radiation

Fading

Fresnel zone

Free space

Inversion (meteorology)

Kennellyeaviside layer

Near and far field

Radio frequency

Radio horizon

Radio propagation model

Rayleigh fading

Ray tracing (physics)

Schumann resonance

Skip (radio)

Skip zone

Skywave

Tropospheric propagation

TV and FM DX

References

^ H. P. Westman et al., (ed), Reference Data for Radio Engineers, Fifth Edition, 1968, Howard W. Sams and Co., no ISBN, Library of Congress Card No. 43-14665 page 26-1

^ Demetrius T Paris and F. Kenneth Hurd, Basic Electromagnetic Theory, McGraw Hill, New York 1969 ISBN -0 048470-8, Chapter 8

^ Westman Reference data page 26-19

Larry D. Wolfgang et al., (ed), The ARRL Handbook for Radio Amateurs, Sixty-Eighth Edition , (1991), ARRL, Newington CT USA ISBN 0-87259-168-9

Further reading

Lucien Boithais: Radio Wave Propagation. McGraw-Hill Book Company, New York. 1987. ISBN 0-07-006433-4

Karl Rawer:Wave Propagatiom im the Ionosphere.Kluwer Acad.Publ.,Dordrecht 1993. ISBN 0-7923-0775-5

External links

Wikimedia Commons has media related to: Radio propagation

Online Propagation Tools, HF Solar Data, and HF Propagation Tutorials

DXing.info - Propagation links

Solar Cycle 24 and VHF Aurora Website (www.solarcycle24.com)

Ionospheric Prediction Service - Australia

Unusual HF Propagation Phenomena. 13 Apr 2009 Includes useful recordings each type. Retrieved 9 Oct 2009.

HF Radio Propagation Software for Firefox - Propfire Firefox plug for monitoring radio propagation, website utility to display HF radio propagation status and article on understanding HF radio propagation forecasting

RadioWORKS A radio wave propagation and antenna length calculator

SWDXER The SWDXER - with general SWL information and radio antenna tips.

Space Weather and Radio Propagation Resource Center Live data and images of space weather and radio propagation.

ARRL Propagation Page The American Radio Relay League page on radio propagation.

The Basics of Radio Wave Propagation A resource by Edwin C. Jones (AE4TM), MD, PhD, Department of Physics and Astronomy, University of Tennessee.

"NZ4O 160 Meter Propagation Theory Notes". A website dedicated to layman level explanations of "seemingly" mysterious 160 meter (MF/HF) propagation occurrences. http://www.wcflunatall.com/nz4o5.htm. 

Dynamic Radio Propagation Data Constantly updated radio propagation data pulled from various sources.

The following external references provide practical examples of radio propagation concepts as demonstrated using software built on the VOACAP model.

High Frequency radio propagation de-mystified.

Is High Frequency radio propagation reciprocal?

How does noise affect radio signals?

The following external link is designed for use by cell phones and mobile devices that can display content using Wireless Markup Language and the Wireless Application Protocol:

WAP/WML Space Weather and Radio Propagation Resources Space weather and radio propagation resources.

v  d  e

Radio spectrum

ELF

3 Hz

30 Hz

SLF

30 Hz

300 Hz

ULF

300 Hz

3 kHz

VLF

3 kHz

30 kHz

LF

30 kHz

300 kHz

MF

300 kHz

3 MHz

HF

3 MHz

30 MHz

VHF

30 MHz

300 MHz

UHF

300 MHz

3 GHz

SHF

3 GHz

30 GHz

EHF

30 GHz

300 GHz

v  d  e

Electromagnetic spectrum

 shorter wavelengths       longer wavelengths 

Gamma rays  X-rays  Ultraviolet  Visible  Infrared  Terahertz radiation  Microwave  Radio

Visible (optical)

Violet  Blue  Green  Yellow  Orange  Red

Microwaves

W band  V band  Q band  Ka band  K band  Ku band  X band  S band  C band  L band

Radio

EHF  SHF  UHF  VHF  HF  MF  LF  VLF  ULF  SLF  ELF

Wavelength types

Microwave  Shortwave  Medium wave  Longwave

Categories: Radio frequency propagationHidden categories: Articles needing additional references from October 2009 | All articles needing additional references | All articles with unsourced statements | Articles with unsourced statements from February 2010 | All articles that may contain original research | Articles that may contain original research from February 2010

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Gmrs Radios For Personal And Business Communications

If you are thinking about purchasing a walkie talkie, you might to consider GMRS radios before you do that. GMRS is an acronym that stands for General Mobile Radio Service, and it describes a two way radio system that is best used over short distances. These communication devices look similar to walkie talkies but they have much better performance and can work over a much wider range of service. One thing you should understand, though, is that you will need a communication license to operate GMRS radios. Let us take a look at these wonderful radios and find out how they operate and how you can get a license. Since licensing really is the first issue to deal with when using GMRS radios, we need to take a close look at the requirements. First, to get a GMRS license you need to be at least 18 years old and you must not have any ties or obligations to any other governments outside of the United States. You must apply by completing and submitting an application, and paying a small fee of eighty five dollars. The license will allow you and any of your immediate family members to use the device. The license also allows you to use the radios for personal communications, and if so desired business communication as well. You may also use the radios to talk with anyone who is a current and valid license holder. The GMRS bands are not the same as the Family Radio Service, even though they do share some of the same frequencies. The major difference between the two is that the Family Radio Service is free and has use capabilities with many public access stations. Based on current records there are approximately ninety thousand active GMRS licenses out there. While walkie talkies have a fairly limited range, this is not the case with GMRS radios. In a dense city area with tall buildings, cars, and other obstructions, you can expect these radios to operate up to one mile of service. If you are in a wide open space your GMRS radio will easy broadcast up to five miles. The biggest advantage to using these types of radios is that there is no monthly service fee associated with them. With cell phones you must pay your monthly fees to use the units and it can be quite costly. With the GMRS there are no fees, it is free to use your radio once you have purchased your unit and acquired the license. This can be a really big advantage for a business as they have no monthly operating fees to pay when using GMRS radios. These devices are really simple to operate. All you need to do is press the communication button, talk into the mouth piece are of the radio, and you will be broadcasting a message. Listening for a message is also quite simple, just so long as the unit is powered and you do not have the talk button engaged you will be able to hear any incoming messages. The GMRS has really carved out a unique line of users since it was first introduced in the nineteen sixties. These specialized radios are similar to a Ham radio, but they are designed to operate over much smaller distances and serve a much smaller market. If you are a business owner, you find that GMRS radios are optimal for you needs to serve you and your business with cost effective communications. If you are looking to add to your portable radio experience then you need to consider purchasing GMRS radios. Find out more information, reviews, and availability for GMRS radios please visit http://gmrsradios.org

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Frequency Considerations for Recreational 2 Way Radios

If you are in the market for 2 way radios for personal use, you have an immediate and important choice to make: What radio frequency band do you require?

Frequency! 2 way radios obviously utilize 'wireless' communication methods so when using a 2 way radio you are transmitting and sending your message through the air -- the same air that is currently carrying television signals, commercial radio signals, Ham radio signals and literally thousands of signals from other private 2 way radios. The Federal Communications Commission (FCC) has the job of controlling all of these communication signals so they don't run into each other; to accomplish this they have reserved frequency bands for use by certain types of communication (signal sending) devices. There are two frequency bands in use for recreational 2 way radios, these are called Family Radio Service (FRS) and General Mobile Radio Service (GMRS).

In 1996, the FCC reserved a set of radio frequencies they called the Family Radio Service (FRS) band, specifically for short-range 2 way radios (radios that operate no more than 2 miles away from each other) with a small power output (up to 500 milliwatts or one-half watt).

About fifty years before the FCC created the FRS band they had reserved a set of frequencies for higher power 2 way radios that operated over a longer range this is the General Mobile Radio Service (GMRS) band. The GMRS band is for radios with a power output between one and five watts and a range over 2 miles. The FCC regulates the 2 way radios that operate on the GMRS band and requires users of this type of radio to obtain a license and pay a fee. The GMRS license is good for five years and costs .00; the license must be obtained by an adult (the radios operating under the license may be used by minors but only with the licensed adult's knowledge and permission)

When buying 2 way radios, your choice is between a set of radios that operates only on one of these frequency bands or a set of radios that is able to operate on either one of these frequency bands. This determination will obviously have to be made based on the maximum distance the radio users will be from each other. If the radios are to be used within two miles of each other, FRS will be the best (and least expensive) choice. If a greater distance is consistently required, 2 way radios that operate on the GMRS frequency band will be required. If the need for distance is uncertain or if you want the option of occasionally transmitting up to five miles a FRS/GMRS hybrid is the radio set to choose.

Build my first own fm transmitter radio station

I wrote a similar article before about Fm transmitter. That time, i was still a layman. Anyhow, boy turns to be man and so do i. I booked some manuals and started to build my own fm transmitter house with my bro`s help.

I bought some equipments needed to biuld my little fm transmitter house on the internet. First one is an antenna, you should know that the bigger size an antenna the further distance. Then is the transmitter which is the most important part in the processing. We all know this cute stuff is used to transmit a radio wave on any frequency you want. The third thing is power, a transmitter still needs a power supply, and the larger power means the further distance the signal could be transmited while also the higher price. After the transmiting part`s ready, i needed to find another sound termination like CD player or MP3 and a mirophone to transmit. On some aspects you still needed Coaxial Cable to connect your signal with the antenna. lastly a compressor/limiter was needed to keep the sound level of your transmission even and constant.

Things came to the next were so easy. Took out instructions of the fm transmitter i bought through internet and started to putting the things together. Anyway once you had some problem could not solve by yourself you might need the help from the local amateur radio club. However i got my brother for lucky.

What kind of power we need to choose is always a problem which makes us feel confused. Actually we know that all depends on the the height and quality of your antenna, the power of your transmitter, the region you are transmitting from, what kind of signals you are transmitting, the sensitivity of the listener`s radio equipment, and whether or not there are any building or structures blocking the signal. Anyway i made my chioce after considering all the factors arround my brain. What i could say was that it`s quite sensible.

Here we came to the last thing -- setting the frequency of the transmitter radio to transmit on. What i`d like to tell you was transmitting on the wrong frequency could interfere with emergency services and air traffic systems. Generally the frequencies of FM radio is transmit ranging from 88.1 to 107.9 MHz. Each FM station is separated by a 0.02 MHz frequency interval. Remember to check with your local government to determine which, if any FM frequencies you are allowed to transmit on.

Now Kimpaul can`t help to start its first using. Took my baby to the bedroom on second floor, and turned on the CD player pluged the transmitter into it and my brother hold the little fm radio setting the frequency and you konw what the most amazing things happened in my life i could not help to jump high and shouted out "awesome"!

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Shortwave Radio - Our Link to the World

Shortwave radio frequencies are used to stay connected to information from all around the world. Shortwave radios operate in the portion of the radio spectrum which covers the frequencies from 3 to 30 MHz (Mega Hertz).   This is a portion of the band which allows reception of communications for thousands of miles.  This means listeners will be able to pickup news broadcasts, music programs, and other programming from all around the world.  

There are many uses of the shortwave radio band, but the most common communications are:  Domestic broadcasting, international broadcasting to foreign audiences, and communication among amateur radio operators.  A popular hobby of shortwave listeners is referred to as DXing.  In Dxing the goal is to hear as many stations as possible from as many countries as possible all around the world.  Many of these foreign stations provide confirmation in the form of QSL cards, and various other promotional items to shortwave listeners confirming their reception.

Foreign stations often broadcast concurrently on several frequencies.  This is because the best time to hear certain frequencies in different parts of the world is not the same during different times of the day.  Therefore, you have several frequencies to use in your effort to find a particular station on your program schedule.  Generally, the best time to listen for foreign stations is at night.  You can also get great reception at both sunset and sunrise.  This does not mean you shouldn't try during the day, because atmospheric conditions vary and can provide good communication anytime.  The challenge to listening is that atmospheric interference can sometimes make reception difficult.

Shortwave radios use frequencies that are divided into bands.  These bands are identified by the frequency's actual wavelength in meters.  Sometime these bands are marked on the radio along with frequency ranges.  What is important to know is that the bands each identify a specific range of frequencies as in the abbreviated band chart that follows:

Band.........Frequency in MHz
120 m.......2.30 – 2.50
90 m........3.20 – 3.40
75 m........3.90 – 4.00
60 m........4.75 – 5.06
49 m........5.90 – 6.20
41 m........7.10 – 7.60
31 m........9.20 – 9.90
25 m........11.60 – 12.20    
22 m........13.57 – 13.87
19 m........15.10 – 15.80
16 m........17.48 – 17.90
13 m........21.45 – 21.85
11 m........25.60 – 26.10

A great source for current program scheduling is "The NASWA WWW Shortwave Listening Guide" which can be found at http://www.naswa.net/swlguide/.

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The Many Services Which are Available to Customers of Radio Shack

To buy our radios and other electronic products there are many stores that you can go to. One of the well known electronic stores that you will find is that of Radio Shack. This store which can be found all over the country has many products that you will love looking through. You will find many well known name brands as well as the new electronic products for sale.

Besides selling other electronic goods Radio Shack also produces and sells it own brand of electron products. These are Presidian, Accurian, Gigaware, Optimus, Enercell, MyMusix and Voicestar. Their discontinued products are under the brand names of Archer and Realistic. These many different names brands provide customers with a selection of goods that they can use.

The original idea behind the opening of the Radio Shack chain of stores was to have a place where amateur radio uses could find the various parts that they needed. From these many different radio parts and pieces these customers then had the ability of building a custom designed radio that would fit their needs and purposes. The first Radio Shack was operated by two brothers.

Theodore and Milton Deutschmann later sold the Radio Shack business to Charles Tandy. At this point the Tandy Radio Shack began to grow and expend its business dealings. Today while Radio Shack still provides its customers with products for their radios and musical systems, it has other products that you can choose from. These products are the ever popular wireless phones, satellite radio systems, notebook computers and even a product which is called PC Modding.

While it is fun to browse around in this store and see the many items that you can make use of there is more goodies in-store for you. To cater for the large amount of people who prefer to do their shopping over the internet Radio Shack has its own web page. On this home page for Radio Shack you will find links which will explain the buying process as well as the paying for your goods process.

Radio Shack also has its own magazine which you can access online. This magazine covers many interesting subjects. This magazine will show you how to make various items like your own podcasts, interesting souvenirs. These are just of the many services which you can expect when you are look through the many services which are available to customers of Radio Shack.

Key Benefits of a Digital Radio Scanner When Looking For a Handheld Radio Scanner

When you are searching for a handheld radio scanner, you will find many different choices, including a digital radio scanner. Here are some basics that will help you decide if one of this type is right for you.

A radio scanner, or police scanner as it is often called, is a receiver that can be used to monitor VHF and UHF radio systems. Any type of information transmitted by two way radio can be heard with these scanners. Most offer a feature that can be set to ignore or accept transmissions from specified departments.

In the past, scanners could only monitor a few different channels. Depending on which you select, a mobile radio scanner is now capable of monitoring hundreds of channels between 30Mhz and 3Ghz. The VHF to UHF is between 300Mhz and 3Ghz and is used by public service agencies with their two-way radios.

Very high frequency (VHF), ranging from 30 MHZ to 300 MHZ, is used for FM radio broadcast, television broadcast, land mobile stations for emergency purposes, military, business, amateur radio, marine communications, air traffic control communications, and air navigation systems.

Other than being used in law enforcement agencies, police scanners are also used for high frequency communication in corporations and in emergency services to keep their information private.

Because of the rise in the number of intrusions taking place in their communication devices the corporations began to broadcast digitally. This move opened up the market for digital scanners as technology kept pace with the advances made by the corporations.

A digital radio scanner is the latest version of popular scanners. They are designed to receive and process digitally encoded signals transmitted between various two-way radio systems in public use.

The reason these scanners are called "digital" is because they are designed to be compatible with radio signals transmitted in digital mode rather than the conventional analog mode, although older analog signals and newer digital transmissions are both in use. Most of the digital scanners will still process the analog signals too.

Digital signals are less affected by interference and noise, and deliver usable information better at the extremes of their range when analog signals become unpredictable. Some digitals also come equipped with the trunk tracking feature to make use of trunk lines. Most police and fire departments use radio frequencies and channels that are tied together through a trunk system.

When you are looking at a handheld radio scanner, more than likely you will come across the phrase APCO P-25. This is a set of standards for digital radio communications used by the federal, state and local public safety agencies in USA for communication between them. Non-encrypted digital signals meeting the APCO P-25 standard can be processed by digital radio scanners.

Some people will want to get a scanner because they enjoy following police and emergency vehicle responses, or they are assisting the police in some way as a volunteer. Auto racing fans often get radio scanners so they can listen in on the team's communications.

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Basic Guide To Ham Radio

Amateur radio (also called ham radio) is a hobby enjoyed by about 3 million people throughout the world and over 600,000 in the USA alone. It is about communications and the multiple ways of communicating through radio waves.

What most people do not know about this hobby and the people that are operators is that they are one of the most used groups as means of emergency communication, when other conventional means of communications fail, in a disaster situation for example.

Local communications is one of the first things to go away in case of a disaster such as hurricanes or tornadoes. Phones and electricity go down and the only thing left is amateur radio operators that can operate from a battery and a piece of wire for an antenna.

These operators have networks set up all over the world that can be immediately activated and used to coordinate disaster relief activities. Recent examples include the 2001 attacks on the World Trade Center, when amateurs worked weeks side by side with rescue crews supplying communications.

Amateur operators were also involved this last year in all the hurricanes that we had all over the world. They have been watching and reporting the advance of the storms, setting up nets to pass traffic for rescue groups as well as passing health and welfare traffic to people trying the get in touch with relatives in the stricken area. They carry a message out to someone that says we are ok and we are alive and that is always great.

The National Weather Service might have great radars, but a radar can't see the storms like human eyes can. Just ask someone that works for the weather service about the role of radio operators and you will get one answer- they are the "eyes" of the National Weather Service. They are on duty any time that there are storms in the area. Any time of day and night these people are watching storms and reporting what they see.

Their accurate reports can be used immediately by the weather service and further by the local radio and TV stations which broadcast the reported data to the public.

Amateur radio operators are saving thousands of lives each year, yet this gets almost no recognition. And the kicker is that their service is at no cost to the public. As mentioned before, amateur radio is a personal hobby; this means the operators buy all their own radio equipment.

And they use it for public safety. Whenever needed to warn the public of danger.

Are they heroes? Think about it.

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How to Shake the Winter Blues with Amateur Radio - HAM Radio

How often have you seen a child running to a window and peering out at the falling snow with a big smile and a pumpkin like face. Most children love snow, and the more the better. I know when I was a child I certainly loved the snow, and for two reasons, if often kept me home from School that day, and it made for a very fun day playing in it. As we grow from children into adults we often stop playing in the snow and having such fun, especially if were males, since we have to act the tough and rugged way instead of showing emotions like a child's joy. Those that are lucky enough to have a playful spouse or children, know that this is a bunch of crap. Joy and having fun, is something we all need to experience, a world without laughter and fun would not be a very nice place for anyone.

On them cold winter days if your an adult and you find yourself alone, or with empty time on your hands, why not head to your den, or office where you have your own gateway to the world, no, I am not talking about the internet, I am talking about Amateur Radio or HAM Radio as it's often called. Amateur Radio has been around for years, it is not amateur or simple as the name suggests, but instead it gets it name amateur do to the aspect that its members or operators work outside of a governmental or commercial field.

Amateur Radio is very fun, and it opens up a whole new world to anyone that does it. You can communicate to folks literally  around the world with it, and it has been used in times of natural disasters and even war, to communicate with survivors. Communication is mostly done with voice transmission, like talking on a telephone or to someone in person, but a lot of the more seasoned operators will also chat using a series of codes, and some even use Morse Code to talk back and forth. You often can tell if someone is an Amateur Radio operator because of the large antenna outside their home.

Most newcomers to the Amateur Radio hobby, start by joining a local club or group, if there are none locally you can search the internet, where you will find numerous groups and chat rooms on the subject. You may also wish to purchase and study some books on Amateur Radio for beginners. There are quite a few things that one must become aware of when starting the hobby in their home, such as the type of equipment to use and purchase, antenna, license, getting your stations call sign, fees and other things.

Again, the best way to get started is by joining some local on online groups, and reading books for beginners. It may seem more complicated and overwhelming at first, then it needs to be, as there are an estimated two million Amateur Radio owners and operators around the world. So, why not get started today in the exciting hobby of Amateur Radio, it just may be what you need during them long, cold months, to help shake the winter blues.

There is a website that describes numerous activities and other methods to help eliminate the Winter Blues, this website is called: Winter Activities - and it may be found at this url: http://www.winter-activities.com

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