The LPD (Low Power Device) channels are dedicated for civilian communication within the UHF frequencies, as much as PMR446, another free band. LPD channels are located in the frequency range 433.075–434.775 MHz and include 69 channels with a step of 25 kHz. You can see them in the table below. Many countries allow to use the channels without a license, but you should meet some requirements. Usually, it is allowed to use walkie-talkies only with a built-in low-power antenna (no more than 0 dBi). The maximum power of the radio mustn’t exceed 10 mW. In many countries, the CTCSS or…
PMR (Personal Mobile Radio) – is a standard for unlicensed radio communications, used in Europe, but prohibited in the United States and Canada. Depending on the country, the number of channels and terms of use may vary. PMR channels This communication standard includes 8 channels with a step of 12.5 kHz, in the range 446.00625–446.09375 MHz. The maximum permitted power for walkie-talkies in this standard should not exceed 0.5 watts. This condition distinguishes the PMR446 channels from the LPD frequencies, where the maximum allowed power is only 0.1 watts. Unfortunately, 0.1 watts and even 0.5 watts are too little for comfortable communication.…
Jump to LPD 433 MHz Jump to PMR 446 MHz A walkie-talkie is a remarkable way to communicate through the globe. As we know, radio waves spread throughout the Earth and even in space if only don’t meet any obstacle. However, we should use them legally, and the laws in different countries are different too. A two-way radio is used by government and military forces, and you mustn’t interfere with their communication. Otherwise, you are gonna be fined. There are special legal bands on different frequencies that are allowed to free usage for citizens. Let’s see, what are free walkie-talkie…
Radio stations became widespread during World War II when the need for fast communications over long distances increased. In those days, a stationary radio was used, but it was huge, and communications men carried such 2-way radios after their officers. Walkie-talkies also already existed, but they were far from a modern compact walkie-talkie we have now. What does any modern walkie-talkie consist of? A receiver of the radio station is responsible for converting radio frequency signals into acoustic vibrations the human ear is accustomed to detecting. First, the received signal is filtered out and increased, then there is a decrease in…
Picking up a two-way radio for the first time? it’s quite tricky to figure out how to talk through this device. I hope you purchased a walkie-talkie that does not require a license to use, or you already have this permission. Otherwise, men in black may knock on your door and report that you have problems! I’m joking, but this is true: if you use the wrong frequency without a license, you could get a large fine. Don’t want to lose a large amount of money? I would not want to either. Free frequency in the USA – FRS (Family…
A refractor, or a lens telescope, is the oldest type of telescopes. It was invented in 1609 by Galileo Galilei and was updated in consequence. Firstly, a refractor used two lenses: convex as an objective and concave in an eyepiece, that caused spherical and chromatic aberrations. This scheme was supplemented by a second lens of different sorts of glasses in the objective to avoid visual distortions. Now, an achromatic refractor it`s a classic at astronomy: it gives a good image and doesn`t take too much money. If you want the best quality of image, then you should pay attention to…
Catadioptric telescopes are compact with high optical capabilities. Since a light beam refracts several times inside the optical tube before going out into the eyepiece, the focal length of such telescopes can be very large. Such telescopes worth the money, they produce a high-quality image. Often they can be equipped with a computerized mount. Due to their design, catadioptrics produce different image distortions. Optics for catadioptric telescopes can be constructed inside an open or a closed pipe. The closed optical design is a bit heavier, but it protects lenses and mirrors from dust and damage. Telescopes with an open design…
In 59 years after Galileo`s discovery, Isaac Newton designed the first reflecting telescope, based on the scheme of Scottish astronomer James Gregory (his book “Optica Promota”, 1663 year). A reflector uses a mirror instead of lenses to gather light. After the hit in an objective, a beam of light goes to the opposite mirror and turns back to the eyepiece. Types of reflecting telescopes and how do they work There are several most famous reflecting telescope designs: Cassegrain. The main big mirror is concave or parabolic. It transfers light to a small convex secondary mirror. The system suffers from a…
Bresser Binoculars 8×40 is a very bright image, perfect for dusk. Wide field of view. Rubber cover. Binoculars Bresser Hunter is designed, of course, to meet the needs of hunters, bird watchers, and all nature lovers. They are cheap and perfect for everyday use. The models are made in a classic design with Porro prisms and feature a wide field of view and increased image brightness. Today we are looking at the Bresser Hunter 8×40 binoculars in detail. Review Perhaps Bresser Hunter 8×40 is the best low-cost model for observations in low light. An 8x zoom ratio with 40mm lenses…
Wide field of view and prism BAK-4. Durable, hard to break. Cheap. Easy to adjust. Metallic Russian binocular KOMZ BPC5 8x30M Baigish released in 1982. Since then his image quality noticeably improved (yellowness went away) and instead of old plastic (bakelite) eyecups, he acquired rubber ones. It is made with the classical Porro scheme and central focusing system. If you have different acuity of the right and left eyes, there is an additional adjustment of the right eyepiece. You can change diopters from -5 to +10. D additional is from -2.5 to +2.5 diopters. The binoculars are compact and lightweight…
Barlow lenses were invented and developed by Peter Barlow and consequentially bear his name. The lenses are not only used in telescopes but also in microscopes to serve the purposes of medicine, science, etc. this type of optical lens is usually used in combination with other different types of optics as well as optical systems. The result of such use is a substantial increase of the focal length of the system where Barlow lenses are used. Barlow lenses are widely used in telescopes. It is a very efficient way of increasing the magnification of your tool. The lens is simply…
Every telescope can be chosen on the basis of two criteria because one of the main characters that will be taken into account is either aperture or focal length. Aperture in a telescope is the objective length diameter when it is referred to a refracting telescope or the primary mirror when it is referred to reflecting telescope. So, if you switch to greater focal length, it is clearly better to observe remote objects in space such as the Moon, planets, etc. or if you require better observation of DSO (deep space objects) such as galaxies getting a device with greater aperture figures is better.
There are several types of telescope mounts that can be purchased today. Every type serves specific needs and purposes and suited for certain individuals depended on their level and ability to use the tool. All of the telescope mount tripods differ in price and have different features. There are four major types of mounts that can be found on the market today. Each mount has its specific name, so that will be much easier to distinguish them among each other. The range of these types can be defined as follows: Alt-Azimuth Equatorial Mount Dobsonian Mount (which is named after Mr.…
Over the years, people have always adored to get closer to observation of the wildlife and watching birds’ behavior, their habits and actions captivated the minds of the observers. Indeed, obtaining better focus as well as getting closer to the creatures often allows getting much better material for case studies and purely pleasurable moments for watching the wildlife. To do that it is very important to choose the right binocular that will serve you as an impeccable tool. You should choose accordingly on the basis of personal preferences in terms of tool’s lens sizes, waterproofing, magnification and design of the…
I met this little friend on one trip; he was attached free to my hotel room. His name is Baigish 50×50 and he is Russian. He was created on the manufactory called KOMZ – an optical-mechanical factory in Kazan, which has been existed since the time of the Soviet Union. KOMZ Baigish 50×50: a short review Well, it seems that a true increase in the binocular is only 15x, not 50x, as it signed. At least, I can find just a model 15×50 on the official site. (Truly, I could not find this model on the official site, so I…
When you go to the mountains, it’s not the best idea to rely on a cellphone for connection to your friends. Cellular coverage in the mountains is unreliable, and you risk ending up without a means of communication. Remember that it may be very dangerous in the mountains to stay without a connection. It’s not necessary if you go to the popular skiing slopes, but what if there is nobody around, and you need help? Sometimes it may be a question of your safety or even a risk to your life. So, this article is about how to choose the…
Moon is the best object for beginner observers and not only for them. Its close location to the Earth allows stargazers to use not too expensive telescopes and even binoculars. Moreover, you can see the biggest sights with the naked eye. Therefore, can you imagine that having a powerful telescope, you can see the famous base of astronauts and traces of their rovers on the Moon’s surface? The Moon viewing can open to you many surprising and even strange things, like these: (here will be the photos) Lunar phases A month of the Moon continues 29 days. This time is…
There are not only such telescopes that we are used to seeing in astronomical observatories and personal plots of neighbors. There are also infrared telescopes and radio telescopes. The infrared telescopes are used in astronomy to study the thermal radiation of space objects. As you know, all bodies, both liquid and solid, heated to a certain temperature, emit infrared spectrum energy. The wavelengths emitted by the body depend on the heating temperature: the lower the temperature, the longer the wave and the lower its radiation intensity. The radio telescopes are widely used in astronomical researchers to study electromagnetic radiation of…
Hello, dear visitors! Make yourself at home, whether you at home or not. By the way, did you ever feel that your real home is not the place, where are you currently live? I did. Some of us suppose that home is not a place but is the soulmate, who we will meet someday. The others find a home in different cultures, which they feel an identity with. But what if our souls are from far-far away? Far in a deep sky, where time transforms and disappears, and substance burns. Did you know that the time distance between our planet…
How does night vision binoculars work? Usually, people use night vision devices for hunting, terrain orientation, watch night animals and so one. In other words, they use it in outdoor. There must be the moonlight or light of stars. The principle of night vision devices work is the increase of rushlight, which is not enough for our eyes. Any night vision binocular does not work in absolute darkness without special assistance. If you stay in a closed room without windows or any least sources of light, your night vision device won’t help you if only it uses infrared light. Depending…