Amateur radio in space

Amateur satellite service is a project sponsered by various entities and carried out by astronauts and cosmonauts on International Space Station who have license. Shuttle Amateur Radio Experiment (SAREX) was its previous name.
Amateur radio operators all over the world speak with astronauts with the help of  their mobile, home radio stations. To establish communication low power radios and small antennas can be used. Even with the help of laptops it is possible to send digital data to space station.
The space station occupants while working have breaks. During break, some of them spend time communicating via amateur radio.
With the help of amateur radio, we can communicate with astronauts in space. This is very useful to students as they get connected with astronauts so that they could learn more new concepts and develop their knowledge.
How to Call Space Station Astronauts on the Radio?
A ground station contains a device capable of both transmitting and receiving radio waves near the 145 megahertz frequency. The ISS radio transmits signals at 145.80 MHz and receives signals at either 144.49 or 145.20 MHz, depending on its orbital location.
During the 10-minute communication sessions, Ransom said, students usually ask the ISS crew what they do in their free time, where they are and what it looks like out their window.
Thus amateur radio in space is very useful and is one among the best methods to communicate with astronauts in space.

History of Ham

The birth of amateur radio starts, of course, with the invention of the radio. There are many contributors to the birth of radio such as Guglielmo Marconi, Nikola Tesla, ect. Brilliant Scottish scientist named James Clerk Maxwell set the next foundations in place.Maxwell was a theoretical scientist and sought to express physics in terms of mathematical relationships.
Maxwell's work culminated in 1873 with the publication of a book called "A Treatise on Electricity and Magnetism". In this he developed equations, now known as Maxwell's Equations that defined electromagnetic waves.

 No matter who gets the credit, one thing is clear, these first radio operators were the pioneers of amateur radio. In fact, by 1909, the first amateur radio club, The Junior Wireless Club, was organized in New York. The earliest transmitters consisted of spark transmitters and these continued to be used for many years. It was only in the 1920s with the cost of valves / tubes coming down that spark transmitters stopped being used. The phenomenon of radio waves gained a lot of publicity - the fact that signals could travel between two points with no wire even held a form of magical mystery and public demonstrations were sometimes given. These factors provoked people to learn about radio communication and to become radio amateurs.

In the early days in the history of ham radio it was not envisaged quite how radio would develop. Anyone was allowed to transmit and there was no regulation. However as radio started to be used for commercial uses it was agreed that licensing would be required. In the UK licenses started to be issued in 1904, and this occurred around the same time in many other countries. Callsigns also started to be issued, but this occurred a little later. As the years passed, the history of amateur radio showed that technology developed and new techniques were used. However the same pioneering spirit of some of the early radio amateurs was retained, with many radio hams contributing to the development of technology in many ways.

Events:
 It was the sinking of the RMS Titanic on April 15, 1912 that prompted new international radio laws which also affect amateur radio, including frequency restrictions and operating procedures.

World War I: By 1917, World War I had put a stop to amateur radio. In the United States, Congress ordered all amateur radio operators to cease operation and even dismantle their equipment.These restrictions were lifted after World War I ended, and the amateur radio service restarted on October 1, 1919.

World War II: During the German occupation of Poland, the priest Fr. Maximilian Kolbe, SP3RN was arrested by the Germans. The Germans believed his amateur radio activities were somehow involved in espionage and he was transferred to Auschwitz on May 28, 1941. After some prisoners escaped , the Germans ordered that 10 prisoners be killed in retribution. Fr. Kolbe was martyred when he volunteered to take the place of one of the condemned men. He is considered the Patron saint of Amateur radio operators.
Again during World War II, as it had done during the first World War, the United States Congress suspended all amateur radio operations.

NATO Alphabets

Can you hear me now?
Are you able to hear me now?
If what you've got maybe this failure to communicate, then it may indicate that it’s time to place the NATO sound alphabet to use. Anyone who’s worked with the military is conversant in it. Even civilians may use a variation when they’re trying to be understood over the phone.

The NATO sound alphabet was adopted within the 1950s. The 26 codewords are assigned to the 26 letters of the English alphabet. Several variations of spelling alphabets have existed through the years The sound alphabet we hear commonly today was adopted for radio communication by the International Maritime Organization in 1965.

The NATO sound alphabet is employed today in military communication and radio communication, whether you’re trying to be understood across time zones or across space. Why the necessity for a phonetic alphabet? If you think that you've got a loud office, just imagine trying to signal military landing locations amid gunfire and radio interference. Every letter counts and clear communication just might save lives.

To create a sound alphabet, you merely replace the letter that you simply want to mention with a word that starts with an equivalent letter, an idea which is named acrophony. For example:

‘C’ is often replaced by ‘Charlie’.
‘G’ is often replaced by ‘Golf’.
‘O’ are often replaced by ‘Oscar’.

Some phonetic alphabets use code words that revolve around a selected theme; for instance, several older alphabets used names of cities and countries as code words (e.g. ‘Amsterdam’ and ‘Italy’). Other phonetic alphabets use code words which are supported other factors, and most notably on intelligibility, which reflects how easy the code words are to know in conditions where it’s difficult to speak (e.g. ‘Able’ and ‘Baker’).

There are two main advantages to learning the NATO sound alphabet today compared to other alphabets:
• The NATO alphabet is that the main sound alphabet employed by many countries, organizations, and individuals around the world, meaning that tons of individuals, and particularly those that encounter it during a professional setting, are likely to be conversant in it. Accordingly, this is often the sound alphabet that folks are presumably to simply understand if you employ it to speak to them, and it’s also the sound alphabet that folks are presumably to use when lecturing you.
• The specific codewords within the NATO sound alphabet were chosen supported extensive testing, as they ensure mutual intelligibility between speakers from different linguistic backgrounds, by virtue of being easy to pronounce and recognize.


Accordingly, the NATO sound alphabet consists of 26 codewords, each of which represents a special letter of the English alphabet.
These words are:
Alpha, Bravo, Charlie, Delta, Echo, Foxtrot, Golf, Hotel, India, Juliet, Kilo, Lima, Mike, November, Oscar, Papa, Quebec, Romeo, Sierra, Tango, Uniform, Victor, Whiskey, X-ray, Yankee, Zulu.

In the NATO alphabet, punctuation marks are mentioned by their name, with a couple of exceptions: a hyphen (-) is mentioned as a touch, a period (.) is mentioned as a stop, and a percentage point is mentioned as some extent or as a decimal.

If you opt you would like to find out the NATO sound alphabet, you'll roll in the hay employing a sort of methods, like by writing down the code words on handmade flashcards, or by employing a memorization software. you'll also prefer to simply memorize the code words so as, employing a list of the code words within the NATO sound alphabet. Potentially, you'll recite these words with a rhythm or tune that creates the code words easier for you to recollect, though this isn’t crucial.

The next time you’re having a Whisky Tango Hotel moment, you'll thank military communicators for helping you get your point across more clearly.

J POLE ANTENNA

J POLE ANTENNA:
    J pole antenna is one of the popular antenna with 2meter in height commonly used in amateur radios particularly on VHF and UHF bands. It was fi invented by Hans Beggerow in 1909. It was used in zeppelin airships. It is end fed vertical half wavelength antenna. It is also known as J antenna and end fed zepp. It is omnidirectional in nature. When j pole antenna is properly connected , it clearly makes good match for 50 ohm coaxial transmission line. Commonly impedance matching is done for J pole antenna. The transmitter is matched to output impedance by a series band section of transmission line. The Jpole antenna is more sensitive to metal objects in surroundings. This is due to lack of true ground plane. This can be reduced by feed polarity. It can be avoided by making a distance of one or two wavelength away from filling cabinets.
                           

     J pole antenna is of different types,
• Roll up emergency J pole
• Copper pipe J pole
• Fold up copper pipe J pole
• Double Jpole
• Super J pole
  Roll up emergency antenna is trivial to build. The disadvantage of this antenna is , fairly fragile and has narrow bandwidth because of small diameter of the wires. The bandwidth can be increased by the usage of ladder line for impedance match. And also by connecting piece of coax to the radiating part. The construction of copper pipe J pole is ease for durability and bandwidth. Fold up copper pipe J pole antenna is too large and hard to carry. It  has small durability. The antenna which consist of number of half wavelength vertical elements separated with half wavelength tuning stubs feed with folded matching stub is called Super J pole antenna. It is co-linear vertical antenna .

MONOPOLE ANTENNA

MONOPOLE ANTENNA

A monopole antenna is a type of radio antenna consisting of a straight rod-shaped conductor, placed  perpendicularly over some type of conductive surface, called a ground plane.

 The monopole antenna was invented in 1895 by  Guglielmo Marconi; for this reason it is sometimes called the Marconi antenna. Common types of monopole antenna are the whip, rubber ducky, helical, random wire, umbrella, inverted-L and T-antenna, inverted-F, mast radiator, and ground plane antennas.The monopole antenna is an common antenna that is often used on vehicles and other areas were a large conductive flat area is present (“ground plane”). The standard monopole antenna measures 1/4 wavelength in height (λ/4); however, this antenna must be placed on to a large conductive surface to function properly.

The length of the antenna is determined by the wavelength of the radio waves.  The most common form is the quarter-wave monopole, in which the antenna is approximately one quarter of the wavelength of the radio waves. A monopole antenna has an omnidirectional radiation pattern: it radiates with equal power in all azimuthal directions which means horizontal angle measured clockwise from any fixed reference perpendicular to the antenna

POLE BROADCASTING ANTENNA

While using radio broadcasting, the radio frequency power from the broadcasting transmitter is fed across the base insulator between the tower and a ground system. The ideal ground system for AM broadcasters comprises at least 120 buried copper or phosphor bronze radial wires at least one-quarter wavelength long and a ground-screen. All the ground system components are bonded together, usually by welding, brazing or using coin silver solder to help reduce corrosion. Monopole antennas  uses guy-wires for support which is named as masts in some countries. In the United States, the term “mast” is generally used to describe a pipe supporting a smaller antenna, so both self-supporting and guy-wire supported radio antennas are simply called monopoles if they stand alone. If multiple monopole antennas are used in order to control the direction of radio frequency (RF) propagation, they are called directional antenna arrays.

Yagi-Uda antenna

Yagi-Uda antenna

Yagi-Uda antenna is the most regularly utilized kind of antenna for TV reception, many other domestic and commercial applications. It is an electromagnetic device that collects radio waves.The Yagi-Uda antenna derived its name from its two Japanese inventors Hidetsugu Yagi and Shintaro Uda.

It is mostly known for simple utilization and better execution. Itis highly appreciated for its high gain typically greater than 10 db and directivity. The gain and directivity of the Yagi antenna enables the receiving capacity by improving better degrees of noise ratio to be accomplished, and by reducing interference levels by just getting signals from a provided direction. The frequency of this antenna extends around 30 MHz to 3GHz which is of the VHF and UHF band range and covers about 40 to 60 Km.

Fig: 1 Yagi-Uda antenna

Construction of Yagi-Uda Antenna:

A Yagi-Uda antenna was seen over pretty much every house during the past decades. The parasitic components and the dipole together form a Yagi-Uda antenna. The Yagi antenna design has a dipole as the principle transmitting driven element to which power is applied from a feeder.

The ‘parasitic' components draw power from the driven element and re-radiate it. The stage is in such a way, that it influences the properties of the entire Yagi antenna on the whole, making power be focussed one specific direction and expelling out other directions.

The amplitude and phase of the current that is induced in the parasitic components is decided on their length and the spacing among them and the dipole or driven component. In this event if a component is longer than the resonant length, it gets inductive and shorter, it gets capacitive.

Fig: 2 Components of Yagi-Uda Antenna

There are three kinds of component in a Yagi antenna:

   1. Driven element:

 It is the Yagi antenna component to which power is applied and is a half wave dipole.

   2. Reflector:

 The reflector component is made to be about 5% longer than the driven element and it will have one reflector. It is behind the driven component.

Further reflectors behind the first make no difference to the reception apparatus performance. The reflecting plate gives a slight improvement in execution.

   3.  Director:

These are made to be shorter than the driven element. There might be none, one or more directors in the Yagi reception apparatus. These are put before the driven element, toward the maximum sensitivity. Normally every director will include around 1 dB of gain in the forward direction.

Designing:

For designing this antenna for the given frequency, the following design specifications are should be followed.

Fig: 3 Designing specifications 

Radiation Pattern:

The directional pattern of the Yagi-Uda antenna is highly directive and the radiation patterns are:

Fig: 4 Radiation pattern

The minor lobes are suppressed and the directivity of the major lobe is increased by the addition of directors to the antenna.

The antenna exhibits a directional pattern consisting of a main forward lobe and a number of spurious side lobes. The main one of these is the reverse lobe caused by radiation in the director of the reflector. The antenna can be optimised to either reduce or produce the maximum level of forward gain.

Advantages:

The Yagi antenna offers numerous advantages over different sorts of antenna in numerous applications.

• High gain is achieved.
• High directivity is achieved.
• Ease of handling and maintenance.
• Less amount of power is wasted.
• Broader coverage of frequencies.

Disadvantages:

The negative factors that needed to be taken care while constructions of Yagi antenna are:

•  Long for high gain
•  Prone to noise.
• Prone to atmospheric effects.

Fox Hunt

FOX HUNT:

Transmitter Hunting, or (T-hunting, fox hunting, bunny hunting, and bunny chasing), is a popular way to combine outdoor activity with the amateur radio hobby. The "Fox" hides a hidden transmitter, and the hunters use direction-finding techniques to locate it. To a radio amateur (or “ham”), fox hunting has nothing to do with animals. It is a sport in which individuals race each other to locate a hidden radio transmitter on a known frequency. Since hams are encouraged to design and build their equipment, the typical fox hunt involves a variety of different receivers and antennas with different capabilities. Some of these can display the received signal strength from the hidden transmitter (loosely measuring distance to the transmitter), while others estimate the compass bearing.

Both of these estimates vary in accuracy and precision depending on terrain, environmental conditions, equipment quality, and the skill of the operator. Fox hunting also serves the purpose of preparing radio amateurs for emergency or disaster operations. Because disaster operations require the concerted efforts of multiple radio operators, it seems fitting to explore how the sport changes if fox hunting becomes cooperative.                                                                                   

When participants combine their estimates of distance and bearing, how much faster can they find the transmitter?

Part of the challenge of fox hunting is that measurements are taken infrequently, only once every few minutes. To win the hunt, every minute must count! In the most demanding scenario, each sensor only gets to take one measurement of the fox transmitter. Locating the fox transmitter from a collection of different sensors is a model-based data fusion problem: combining disparate local observations into a global inference. Without a model that describes how signals from the transmitter arrive at each receiver, the signal reports do not help locate the transmitter. Even with such a model, the effects of terrain, the transmitter’s antenna system, and the environment can cause substantial differences between the modelled signal and an actual received signal. Therefore, we must  remain even-handed about assumptions of the quality of the estimates and the quality of the model.

There are several types of transmitter hunts. Transmitter hunting is pursued in several different popular formats. Many transmitter hunts are organized by local radio clubs and may be conducted in conjunction with other events, such as a radio enthusiast convention or club meeting. Before each hunt, participants are informed of the frequency or frequencies on which the transmitters will be operating, and a set of boundaries that define a search area in which the transmitters will be located. Transmitter hunters use radio direction finding techniques to determine the likely direction and distance to the hidden transmitter from several different locations, and then triangulate the probable location of the transmitter. Some hunts may include limits on the amount of time allowed to find a transmitter. Although many transmitter hunts are conducted just for the fun of the activity, some more competitive hunts will recognize winners in publications and offer awards, such as medals or trophies.

Few of the most famous Fox-hunt types are:

1)Mobile transmitter hunts:

Mobile transmitter hunts are organized events where participants travel exclusively or primarily in motor vehicles. Most mobile transmitter hunts use VHF transmitters and receivers.

Some participants use radio direction finding equipment and antennas mounted on a vehicle, whereas others use antennas that are temporarily deployed in an open window or an opening in the vehicle roof that can be easily rotated by hand while the vehicle is in motion. Other participants employ handheld antennas and radios that can only be used when the vehicle is stationary. Some mobile transmitter hunts require participants to leave their vehicles and proceed on foot to reach the actual location of the radio transmitter. The winner of a mobile transmitter hunt can be either the first vehicle to arrive at the hidden transmitter, or the vehicle that travels the shortest overall distance to locate the hidden transmitter. Mobile transmitter hunts are more popular in North America than in other parts of the world.

2)Pedestrian transmitter hunts:

A regulated sport form of transmitter hunting by runners on foot is called Amateur Radio Direction Finding, known worldwide by its acronym, ARDF. It is an amateur sport that combines the skills of orienteering and radio direction finding. ARDF is a timed race in which individual competitors use a topographic map and a magnetic compass to navigate through a diverse, wooded terrain while searching for hidden radio transmitters. ARDF is the most popular form of transmitter hunting outside North America.

3)Fixed location transmitter hunts:

Some transmitter hunts feature a "mail-in" competition, in which teams in fixed locations work together to locate hidden transmitters, then secretly give the coordinates to the organizers without actually traveling to the transmitter location. The team which provides the closest coordinates wins, thus a team which believes that the transmitter is in the northwest parking lot at 2nd and Elm (if it is there) will beat a team which says that the location is 2nd and Elm. This type of hunt enables participation by contestants who are unable to travel, such as shut-ins, school groups, etc., and requires a greater level of skill and coordination.

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