Couples centuries ago carrier pigeons which couple, starting on the journey were the main , the traveler took with himself. Times changed, but even emergence of small compact radio telephones did not solve a problem completely – range of communication of these devices does not exceed distance of direct visibility between antennas as experts speak.
This distance can be increased in two ways: or to apply system of repeaters (as it is made in systems of cellular communication), or to increase height of antennas. We are convinced of efficiency of effectiveness of the first option every time, dialing number of the mobile phone. As for the second, here not all is so simple as can seem at first sight.
On January 4, 2010 in Dubai the highest building in the world – 828-meter Burdzh the Caliph was solemnly open. If to rise by top of this 828-meter tower arrow, it is possible to contact by means of usual pocket radio station someone at distance about 100 kilometers. It will not turn out any more – in a force of the laws of radiophysics and sphericity of Earth even this fantastic height insufficiently for serious practical use.
From the first satellite to Iridium
The exit, strangely enough, is. It was found after October 4, 1957 when launched an artificial satellite, the first in the history of mankind, of the earth. Then engineers and scientists suggested to place repeater antennas onboard similar devices. After all from the satellite it "is visible" at once a half of the globe, therefore, thus it is possible to provide with communication all population of this half.
On realization of idea billions of dollars and work of thousands of people left. The history of development of space communication in something repeats history of development of computers. So, the first antennas represented cyclopean constructions, tons weighed, and specially trained engineers were engaged in service of the equipment.
Today to be connected to similar to Iridium, anyone can. And, all necessary will easily go in in a backpack pocket, near the old checked compass which got from the grandfather.
Satellite communication systems
That the satellite did not fall to the ground under the influence of gravitation forces, it has to move quickly. It creates certain inconveniences as the orbital repeater rushing with a speed over 7 kilometers per second will be behind the horizon quicker, than you will manage to tell about news of the travel.
In practice of it does not occur as not one is started, and there are a lot of small satellites, sometimes the size of all about orange. Thus the subscriber is transferred from one to another approximately the same as we, passing on the city on the car, we pass from an area of coverage of one repeater to another. That transition was reliable, and loss of communication was excluded before being registered in a network, satellite phone has to be convinced that satellites it "is visible" enough.
In life, alas, not always everything occurs so simply and smoothly. Space is not empty and penetrated by the rigid radiation of our sun which is capable to put eventually completely out of action the equipment installed on satellites. For example, the system which is widely used in the past Globalstar already became almost unsuitable as there did not remain sufficient, for conducting comfortable negotiations, number of serviceable satellites.
As a successful example we will call Iridium (Iridium). 66 satellites which orbits are chosen enter this communication system in such a way that it is possible to achieve reliable and high-quality communication in an every spot on the globe – after all the sky is visible from everywhere, and for satellites of borders does not exist.
Now the system Iridium has no competitors. More precisely, Inmarsat providing with communication sea vessels could become it, theoretically. However, owing to the specialization, that initially was calculated only on stationary devices, and successful compact satellite phones for this network in the market are not present so far.
Alternative to a large number of compact and rather inexpensive satellites is use of the powerful devices launched into a geostationary orbit. Its height is selected so that the spacecraft flying round the earth moved with the angular speed equal to the speed of rotation of Earth. On a surface of our planet it means for the observer that such relay satellite as if constantly hangs in one point of the sky.
It – and is good, and badly at the same time. Plus that it is possible to manage the minimum number of satellites. However such orbits are limited to physical laws, and the spacecrafts which are at the height about 35 thousand km over Earth can appear in not too convenient point of the horizon.
So, repeaters of system of Turaya hang over the equator (two near Kenya, one over Malaysia). It, actually, leads to that if you are in the northern hemisphere, in order that satellite phone "saw" the satellite, will be required opened on the South (towards the equator) a look, and free from obstacles.
In practice such meets not always. So, in mountains, at the closed horizon, you will not be able to call, will not get on suitable height yet, and, going on the North or South Pole, satellite phone of Turaya in general can leave at home – communication all the same will not be.
In summary one curious fact. Satellite phones of some global satellite systems, for example, of same Turaya, have the built-in GPS navigator. It in itself is quite good, but a problem that the tube, without everyone on that of your permission, constantly sends on the server of coordinate of the current location. Who knows – whom and for what this information can be used?
And here in satellite Iridium phones of such receiver is not present and stations of interface in the territory of the Russian Federation are absent as there is no technical capability of "wiretap" also intelligence services that guarantees full confidentiality of negotiations.
We choose satellite phone
We think that you already decided on a network choice is Iridium as other providers have the shortcomings described above, and some are not calculated on work with mobile devices at all. Such satellite phones have some important differences from habitual mobile phones.
Main differences two. The first that satellite phone is deprived of any "frills", it is solid and laconic, after all its main objective – to provide the owner with communication, even in the most extreme conditions. It is a means of communication, and therefore there are no toys, the camera or a musical player. But to break such tube, even having dropped it, it is almost impossible – after all just the same also military that imposed special requirements of developers use.
The second difference – in need of the effective antenna, after all distance to the satellite is great, and without it not to establish connection. Look attentively at the photo where two satellite phones having approximately identical technical characteristics are given:
On the picture at the left – IsatPhonePro, the satellite phone calculated on work in system Inmarsat, and his designers tried to hide the antenna in the case as it is made in mobile phones. Agree, attempt is not too successful – dimensions of the case were such that a tube to call compact it is possible only with some share of humour.
The second satellite phone, Iridium 9555, the antenna does not hide, thus looks quite elegantly and even stylishly. But the main thing, perhaps, there is not a design, but a communication quality which is shown by open , especially in geographical points, unsuccessful from the point of view of a covering. For example, in high latitudes of IsatPhonePro in general refuses to be registered in a network, and Iridium 9555 in the same conditions shows all the merits.
Perhaps, higher quality of satellites of the Iridium system plays a role here. But, most likely, nevertheless matter in the antenna: after all far not incidentally more compact satellite Iridium 9505A phone was laid off and replaced with the device Iridium 9555 which is completed with the external antenna and thus is the indisputable leader of the market around the world, including in Russia today.
Here it is also worth talking about this phone in more detail. In a standard complete set it looks so:
Despite all the high technical characteristics, the tube is compact: has dimensions 143kh55kh30mm, weighing only 266 grams. Keep in mind that to hear a call, it is not necessary to put forward the antenna.
To list, the main functions of satellite phone, a special reason are not present. They are standard, and there is all necessary – from possibility of reception and sending the SMS to a public address system and a voice mailbox.
The regular antenna fixed, however is included in the package the adapter giving the chance of connection of more effective external. The last is especially important that who uses the maximum opportunities of communication, for example, using satellite phone as the satellite terminal to the laptop for what, by the way, the built-in USB port is provided.
That is especially pleasant, any additional knowledge from the owner of phone it is not required, and, actually, use of the device does not differ from habitual mobile phones. A difference only that it is possible to make calls, in literal sense, from an every spot on the globe without restrictions.
That autonomy was maximum, it is possible to add phone with such convenient accessory as the compact superthin solar battery guaranteeing a normal charge of accumulators of satellite phone even in cloudy weather.
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