Who are amateur radio hams

Who are amateur radio hams

This article is a small add-on to a note about shortwave radio amateurs.


Antenna operator EA5FUZ

As we have already found out, communicators-radio operators are engaged in radio communication only in the form of a hobby, because both the written and unwritten rules are limited in the topics of communication only to talk about radio equipment and antennas, about radio sports, radio wave propagation and weather. Radio organizers are satisfied with this, because these are precisely those topics that are guaranteed to be interesting to any of them, and for other purposes, radio transmitters, like any other users, use other channels of communication that have nothing to do with radio broadcasting. What is the difference UKVistov from shortwave? Captain Evidence suggests that VHFs are engaged in making p / l links on ultrashort-wave bands, but the difficulty of classification is that if the short-wave bands are to some extent similar to each other, yes, everyone has their own characteristics of propagation, but in general the same principles are used ionospheric transmission, when radio waves are conventionally reflected from the ionized layers and return to earth at large distances, the various VHF bands sometimes differ quite strongly, which requires very different I have technical solutions.

Since the mass appearance of FM radio stations available for amateur (it could have been both radio models and suitable for commercial frequencies), the popularity of local VHF radio in FM began to grow, which gave rise to the rather stable myth that short waves are difficult and expensive, and VHF is easy and cheap. And in recent times, when Chinese-made portable FM radio stations became penny consumer goods and a new category of people appeared with radio broadcasting licenses obtained only for legalizing these portable radio stations (i.e., in fact, they have no relationship to radio amateurness, despite the formal presence of a call sign) This myth has become even stronger.
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Indeed, local communication in FM is easy for the operator. Easily accessible, as was said, the equipment, plus the simplest antenna on the roof, make it possible to join the club of chatter on the near-radio theme within a radius of two to three tens of kilometers. Often, a local group or individual enthusiasts install a repeater that provides support even for very weak subscribers - remote operators, motorists, and pedestrians with portable radio stations. Then the chat club extends to the entire radio coverage area of ​​the repeater, which in the case of relatively densely populated regions, or in the case of an abnormally large repeater installation height, gives a more or less decent audience to communicate, and the communication turns out to be commercially reliable, since the imperfection of its own equipment is significant least compensated by the repeater. By itself, narrowband frequency modulation is quite good and it was not without reason that it was so popular in commercial communications until it began to be ousted by numbers: it uses its occupied frequency band quite efficiently and, with proper circuitry, allows receiving high reception sensitivity, it is tolerant to inaccurate tuning for a correspondent, it is simply implemented mute sound in the receiver in the absence of a useful signal. Therefore, one should not think that FM is something bad. No, FM is just something very affordable in VHF radio broadcasting.

Local communication is, of course, good, but most radio cameras are not interested in sitting in the same swamp, listening to the same stories of the same correspondents day after day, but carrying out as far as possible communications, because this is sporting interest, of which radio lamination is largely composed. Speaking of VHF, they often speak of almost optical, straight-line propagation of radio waves, which practically do not diffract over obstacles such as a horizon. However, communication beyond the horizon is still possible. Meter-wave ranges and, to a large extent, decimeter-wave ranges, have the possibility of abnormally long-range propagation, when the medium is the atmosphere, receives a temperature inversion and, especially, more or less pronounced temperature layers, in which the radio waves are refracted and waveguidely propagate. Probably the most obvious analogue will be optical fiber, in which light is quite reliably held by reflection from the media boundaries - just like in the tropospheric layers, radio waves are held by the layer boundaries. Such conditions arise, depending on the geographic region, infrequently and unwarrantedly, therefore they are not used in commercial communications, but radio transmitters with simple equipment, usually limited to communication distances of about two to three tens of kilometers, are able to operate stations of several hundred kilometers, and if you are lucky then up to one and a half to two thousand. At the usual time, when the troposphere is relatively homogeneous and has a more or less calculated temperature gradient, this effect is not observed, and communication is really possible only to the horizon.

To increase the range of the repeater, you need to raise it as high as possible. So there were radio satellite satellites. Unfortunately, previously launched satellites with highly elliptical orbits, which at the apogee provided radio coverage of almost a whole hemisphere and several hours of radio visibility, have long been out of order. Everything that works now or is planned to be launched is LEO low-flying, low-power Kubsat with altitudes of the order of 500-700km, the visibility of which usually does not exceed fifteen minutes, and the radius of radio coverage is about two to three thousand kilometers, making transcontinental communications impossible for most. Rumors are also circulating about the launch of a geostationary amateur satellite, or rather, that a commercial transponder will be allocated for radio broadcasting entertainment, but so far this has not become a fait accompli, it does not make much sense to discuss this. According to the types of payload, satellites can be roughly divided into FM repeaters, linear transponders and packet digipiter. Satellites with FM transponders are very popular with beginners because they do not require any serious equipment to start. Theoretically, you can work on a portable with a complete or, preferably, an elongated rubber band, but in practice this is unlikely and succeeds rather as an exception. A typical equipment of a novice satellite lover is a portable directional antenna and a portable radio station.

Since most operators have no more than two hands, one of which is occupied by a radio station and the other is an antenna, they usually use a voice recorder to record the span, to conduct communications without being distracted by keeping a hardware journal and registering communications in a calm atmosphere afterwards. The output power of a satellite is hundreds of milliwatts, so the main difficulty is to receive it, and not to transfer it to it at all. Of course, if at the same time someone else transmits with a much stronger signal (not necessarily at the expense of transmitter power, because it is more profitable to increase the antenna gain), then do not shout over it. But when no one interferes, the power of its transmitter is an order of magnitude greater than that of a satellite transmitter (most laptops are 4 ~ 5W), more than enough even in the case of an elastic band, not to mention a directional antenna. It is necessary to calculate in advance the time and direction of the satellite’s span (online or offline programs) in order to understand where it comes from and how much it will appear and how it will pass relative to the operator on the ground, and it’s easy to direct the antenna by ear to the maximum received signal.

Two satellites are still in operation to relay digital voice. One of them receives analog FM, digitizes it and transmits it down already by digit. The second works only in digital. Technically, they are similar to FM satellites and, with the exception of the need for appropriate equipment, do not differ from the point of view of work on them.

The next step is linear transponders. Theoretically, it is possible to use any modulation within their bandwidth, practically only the telegraph and telephony in SSB is used, but FM is most severely condemned because all the available transponder power, and it is of the order of hundreds of milliwatts, is divided into all retransmitted signals. Telegraph impulse signals and single-band suppressed carrier modulation have low average power. And the frequency modulation has an average power equal to the maximum - regardless of modulation, the carrier level is constant and maximum, which leads to pulling out all the weak satellite resources to service this carrier to the detriment of other signals. That is why FM is tacitly strictly prohibited. For operation on linear transponders, less common CW / SSB equipment is required, and continuous Doppler shift compensation is also required. After all, if FM is sufficiently tolerant to inaccurate settings and for the entire time of the satellite’s passage it is enough to flick a station a couple of times, then CW and SBB require continuous tuning, without which the correspondent will swim away in frequency to complete promiscuity. With advanced operators, everything is automated: based on known TLE (orbit parameters) and known operator position, satellite passage and Doppler shift compensation are calculated for each band, so the rotator automatically directs the antennas to the moving satellite, and the radio introduces a correction itself, eliminating the perceived frequency drift. But the power for transmission is still not required. An excessively strong signal at the input of the transponder will disrupt its normal transmission and, instead of what seems to be a more reliable connection, it will be nonsense for yourself and others.

Batch digipitery and BBS are used for traditional packet communication, and as a segment of the APRS, which will be discussed separately.

Low satellite power is not associated with administrative restrictions, but with the weight and dimensions of the payload and purely technical restrictions on its power. For example, a transmitter with ISS, where there are no problems with power, is heard on the full scale, and the cubsat give a couple of hundred milliwatts to the simplest, not the most efficient antennas.


Repeaters, even in space, are active. And amateurs would like to try passive, methods of establishing long-distance connections that depend only on them. There are two general directions - scattering and reflection. This is a world of high attenuation, so it requires high power, highly directional antennas and low-noise receivers that allow you to pull out weak signals. And it is also a pure sport or, one may say, Proof Of Concept, in which establishing radio communications is valuable in itself, and does not mean pleasant chatter for hours, because it can often take several hours to exchange calls. Most of these relationships are carried out by prior arrangement.

There are always inhomogeneities in the troposphere, which lead to the dispersion of radio waves. As a rule, the dispersion is negligible, but still it is not zero. Therefore, we take an irradiator, say, a range of 70 cm, place it at the focus of a parabolic reflector, at least six meters in diameter, and direct it towards a correspondent with comparable equipment. We bring to the irradiator the power slightly higher than the allowed one and reliably communicate with the correspondent at any time of the year and at any time of the day at a distance of at least 500 thousand kilometers. Yes, in case of occurrence of temperature inversion in the troposphere, the same distance can be covered with incomparably simpler equipment, but there is a case, but here is everyday life. However, it is more interesting to deploy such an antenna to the Moon - the reflection from the Moon (EME) is perhaps the most difficult type of communication on VHF, since the signal attenuation is huge and rather serious equipment is needed to compensate for attenuation, primarily antennas. If one rises higher in frequency (say, one of the popular EME bands is 10GHz), then the diameter of the reflector can be significantly reduced. However, as frequency grows, frequency stability problems per se and separate Doppler shift compensation grow, and centimeter waves in general require completely different engineering solutions to fundamentally the same questions that are well worked out in the range of meter waves and no longer seem complicated. Nevertheless, at the same 10GHz, the connection with dispersion on precipitation - Rain Scatter is relatively popular.


What else can be dispelled or what else can radio waves reflect? For example, from ionized meteor trails. We direct the antenna towards the expected meteor shower and for some time continuously transmit our call sign, repeating it with great speed. If you are lucky, one of our programs will completely reflect on the track and will be received by our correspondent - therefore you need to transfer at high speed in order to have time to slip through the existence of an ionized track, and therefore you need to transfer a long time to get lucky to have such a trace. Then our correspondent gives the answer to us just as quickly and for a long time. The time for which you can successfully transmit information is very little. Specially use such modes in which the transmission rate is very high, higher than the capabilities of a person. When there were no computers, they recorded the telegraph package on a tape recorder and reproduced it strongly accelerated - the receiving party recorded the received and reproduced slowly so that the call sign already transmitted by the telegraph was received by ear. But waiting for the case when our information will be able to reflect on something may have to be very long, and the result is not guaranteed. Sometimes it is possible to communicate very quickly, and sometimes even for a whole day nothing happens - the meteor just will not appear, from the trace of which we will be able to reflect our signal. For example, one of your parcels was successfully received by your correspondent, but his answer still cannot be obtained - without this, the connection does not count, you need a full exchange in both directions. At the same time, you can be in correspondence in a specialized chat for meteor lovers and know that you are actually conducting a connection, and not just transmit to someone who does not know what to expect, but not to spend a full day for a whole day.

You can still reflect the signals from the fuselage of the aircraft. No, seriously, such connections are sometimes made. If the wavelength is less than the object, then it will be able to reflect, and ultrashort waves are shorter than any aircraft, if only it was made from a conductor - fortunately for radio cameras, almost all aircraft are metal, which means you can try. Sometimes they ask whether such a connection carries any danger to the aircraft, its systems or passengers. No, there is no danger. First, the intensity of the electromagnetic field near the plane is extremely small - the distance to it is great. Secondly, the aircraft is a Faraday cage, so its insides, including Pax, are securely shielded by the fuselage. Does it surprise anyone that lightning can get on the plane and it doesn’t cause him any problems? Also, no one is surprised that nothing happens to airplanes from their exposure to radars - specialized devices that constantly operate to communicate with the reflection of radio waves from the aircraft. So from the radioactivity pranks, and even more so, nothing can happen.

Aurora, northern lights are still good. This is an ionized region, so you can work backscattering from it. Inventive radio cameras are ready to use any natural phenomenon or artificial structure for their strange purposes - just to establish radio communication for the sake of establishing radio communication. If this is unclear to you or not interesting - do not worry, you are just one of the most normal people.

What else can you do on VHF? Sports direction finding, which by some misunderstanding is called fox hunting.


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