ARLA/CLUSTER: Manual dos 6m para iniciantes.

[João Gonçalves Costa]

________________________________
De: ct-comunicacoes-e-tecnologias  googlegroups.com [mailto:ct-comunicacoes-e-tecnologias  googlegroups.com] Em nome de Antonio Matias
Enviada: quarta-feira, 11 de Maio de 2011 15:09
Para: ct-comunicacoes-e-tecnologias  googlegroups.com
Assunto: [CT-Com. & Tec.] Manuel dos 6m para iniciantes.


The Six Metre band is located at the lower end of the VHF spectrum and exhibits all of the characteristics that you would expect of a VHF band. This is particularly true during the sunspot minima years when, for the most part, it is similar to two metres. The maximum useable frequency or MUF rarely reaches the ten metre band during this time never mind six metres and consequently the band is fairly quiet except for sporadic E during the summer and, to a lesser extent, the winter months.

[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/noise.ra>You had better get used to listening to a lot of this if you want to work 6m DX!

The proximity of the six metre band to the HF Bands however is what makes the band totally different from it's higher frequency neighbours. During periods of high sunspot activity, the MUF can rise up to and beyond 50 MHz allowing some really spectacular propagation to take place.

Even when the MUF doesn't reach 50 MHz, solar activity can be the trigger that will allow various other types of propagation to occur. In fact six metres is probably the only band that will support just about every form of propagation that you can think of and this is just one of the many things that make it so interesting and, at times, unpredictable.

In the UK, the Six Metre band is notionally split into two halves. 50 to 51 MHz is allocated on a primary basis and 51 to 52MHz is a secondary allocation. In recent years, with encouragement from the UK Six Metre Group, several significant changes have been made to the licence schedule. These have effectively put Six Metres on a par with the HF bands in the UK.

For most people a large portion of the band remains unexplored territory, being given over to the more esoteric modes such as meteor scatter. FM is well catered for, however activity tends to be in small pockets around the country. Several FM repeaters are now well established and will no doubt increase interest in FM activity.

Most SSB and CW operation takes place in the lower 250KHz portion of the band. From 50 MHz up to around 50.08 Mhz the band is populated by various beacons. Around 150 beacons are operational world-wide at present and more are planned. 50.08 to 50.110 is the center of CW activity although, in common with the other bands, CW can be used in the SSB portion also.

50.110 MHz is probably the most monitored frequency in the entire amateur bands allocation. This is the intercontinental DX calling frequency, and is where the first signals during an opening are likely to be heard. Weak DX signals will generally make their first calls on 50.110 MHz; it is for this reason that general operation on or near this frequency is positively discouraged. The UK has one of the highest concentrations of six metre activity in the world, most of whom are listening on or close to 50.110; bear this in mind before calling on this frequency.  50.2 MHz is the local calling frequency although it is rarely used as such. This frequency is the lower limit of the French allocation. Generally local QSO's take place normally within about 30 KHz of 50.2, but should not take place below about 50.15 MHz.

Prior to 1990, very few European countries had access to six metres; the situation has changed radically since then. Almost every European country now has an allocation in the band, and most have numerous keen operators. The exceptions to this are Hungary and Monaco although pressure is being gently applied to both of these countries and we are hopeful for some activity in the near future.

Crossband activity to ten metres still takes place, but to a much lesser extent than before. The ten metre band centre of activity for both crossband and talkback remains 28.885 MHz

Whilst on the subject of ten metres, 28.885 MHz is the focal point for all six metre DX activity. By monitoring this frequency during an opening, you will receive up to date information available about who is working what, where and when. Those of you thinking about operating on six might like to monitor this frequency as it will give you some idea of what to expect. Another useful tool is the DX Cluster.  This can be accessed via the usual two metre or seventy centimetre packet frequencies or via the internet.  For internet users, my advice is to use the UKSMG�s  pages at http://www.uksmg.org/coming_home.htm.  Here you will find the last 100 DX spots for 50MHz from  the OH2AQ cluster, an announcement page carrying requests for information and details of forthcoming expeditions etc. and the �Magic Band Live� discussion area.  Keen 50 MHz DXers  may wish to set this as their internet browser home page.

There are several propagation modes that you are likely to experience on six metres and we will deal with these one by one:

Tropospheric propagation or Tropo, is similar to that you will experience on two metres. Power for power the ranges are much the same and, as with two metres, this is the predominant mode of propagation.

Extended Tropo or tropospheric ducting occurs very much less often than on two metres, in addition signals tend to be weaker and ranges not as great. This is about the only mode that two metres has the edge over six.

Sporadic E on six metres, popularly referred to as Es is ideal for those of you who operate QRP or with small or badly sited aerial systems and, come to think of it, small AND badly sited aerial systems. Whereas two metres will support Es perhaps a dozen times a year for maybe two hours at best, six metres seems to be one long Es opening during the summer. Even if the band appears to be quiet during these periods, there is usually a sporadic E opening to somewhere in Europe. Double hop Sporadic E is not unusual, allowing all of Europe and the near east coast USA to be worked on occasions. Multi - hop Sporadic E, that is three or more hops, is less common but allows fairly long haul contacts; for example to the USA or into central Africa.  Stations with low power and small antenna systems often take advantage of Sporadic E and many successful contacts into Europe and on occasions the USA have been made running less than one watt to a wire dipole in the loft.

Single Hop Sporadic-E
[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/video.ra> Listen to the video carriers covering 6m when sporadic-E exists in Europe
[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/gm.ra>    Listen to the strength of short-skip signals from GM in the south of England (there was Es on 2m at the time)
[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/oh1mdr.ra>        Listen to the strength of single-hop sporadic-E signals (Finland to the UK)
Es Backscatter
[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/backs.ra> Listen to strong sporadic-E backscatter between two stations several hundred miles apart both beaming 240.
[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/on4.ra>   Listen the strong backscatter from ON4 calling the USA
Double-hop From the USA to the UK
[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/kp4.ra>   Listen to KP4 as heard in July 1996 in the UK
[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/w2cap.ra> Listen to W2CAP as heard in the UK

Meteor scatter for those of you not familiar with it is the act of reflecting your signals off the brief ionised trail left by a falling meteor. These can last for up to a minute or more on rare occasions, but more usually for fractions of a second. The operating practice, ranges achieved etc. are the same as for two metres.

[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/ev.ra>Listen to the strong signal from EV5A on meteor scatter using very fast cw.

[http://uksmg.org/content/images/page07.gif]Aurora Borealis or the Northern Lights is capable of reflecting signals from the HF bands through to seventy centimetres. Six metre aurora tends to differ from two in that the distortion of the received signal is usually less, making copy that much easier. Interestingly, if the aurora is strong enough sporadic-E develops which is known as Auroral-Es.

[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/auroras.ra>       Listen to the distinctive tone of a strong auroral signal as recorded in Finland.
[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/oy.ra>    Listen to the clear tone of OY9JD on auroral-Es in Finland.

Photo credit: http://www.geo.mtu.edu/weather/aurora/

Trans Equatorial Propagation or TEP, is peculiar to six and two metres only. This mode allows contacts to be made over paths several thousand miles in length between stations on either side of the equator. The mode is much more common for those stations located in a band around the tropics however, fifty Megahertz will produce TEP propagation, particularly around the months of March and October, as far north as the UK. To date no TEP contacts have been made on two metres from the UK.

[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/zs3e.ra>Listen to ZS3E on TEP in May 1989. It was fantastic back then to think we could work Africa on 6m!

F2. This is the most common long distance propagation mode at HF and can be the cause of some tremendous DX on six metres. F2 openings are the ones that everyone looks for although the one watt to a dipole station is likely to feel a little frustrated.  A dipole will probably allow the DX to be heard, but on most occasions signals are likely to be a little weaker than those from sporadic E, and the competition much greater.  A well sited station with one watt may well be able to work some of the choice DX courtesy of F2, but don't count on it. The sort of DX that you may hear via F2 covers most of the world. The only continent not yet worked from the UK is Antarctica although this is due largely to activity rather than the difficulty of the path.

[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/kg6dx.ra> Click the button to hear how amazingly strong KG6DX in Guam was in Europe via F2 in March 1991.
[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/jh6cyw.ra>        Click the button to hear JH6CYW on CW in Europe in February 1992.
[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/du.ra>    How it is possible to get a callsign (KE0SC/DU) when there is s9 video on the band?
[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/vk8gf.ra> Many will remember well the thrill and excitement and the complete utter panic when we first heard Australia in (VK8GF) Europe in May 1989.and of all places Alice Springs!

One fairly common form of communication on six metres has been left off the list, and that is Backscatter. This is caused by a small portion of the radiated signal being reflected or scattered back in the direction of the originating station from the F2 layer or a sporadic E cloud. Those of you who listen to the HF bands will no doubt already be familiar with backscatter. Signals tend to be weak and watery, but are usually quite readable; by making use of this, it is possible to work those rare squares in the UK that always seemed to elude you, and occasionally some of our near European neighbours.

As with the other bands, hearing and working the DX can be put down to being in the right place at the right time. It is possible to minimise the risk of missing the best openings however by keeping an eye on some basic solar parameters which will give a good indication of the likelyhood of an opening, and even the likely direction from which the DX will be best.

These parameters are the Solar Flux, the A and the K indices. The relative values of these are the best guide to conditions short of permanently monitoring the band. For a more detailed explanation of these see the RSGB Callbook or Handbook; however, here are a few typical examples:

During periods of high solar activity, the Solar Flux will typically be in the two to three hundred region, sometimes greater. Good conditions are generally, but not always, associated with a high solar flux and a low A index. That is a flux above say 180 units and an A index below 8 units. The K index tends to give an indication of the direction of propagation. A low K, say 2 or lower, East West, a high K North South. For example, during the winter months a Flux of 250 combined with an A index of 4 and a K index of 1 indicates a likelyhood of an East West opening. Expect some activity from the Caribbean either side of lunchtime, giving way to the USA during the afternoon. A Flux of 200 with an A index of 7 and a K of 6 would indicate a North South path with say the ZS's coming in at around 1030. Openings to West Africa would be a good bet shortly after lunch. Remember that these figures apply during the sunspot maximum periods only.

Incidentally a high A index, say 30 upwards, would indicate the possibility of an aurora. The higher the figure, the more likely an aurora will take place. The famous aurora of the 13 March 1988 had an A index which peaked 175 units.

The figures associated with these parameters, although dated, are given each Sunday in the RSGB news. More up to date information is provided several times a day by the Standard frequency service transmitter WWV which is located in the USA. It can be heard on 10, 15 and 20 MHz in this country.  Up to the minute reports can be gained from various internet sites.  Nothing of course is guaranteed. These figures are a guide only, the unexpected is liable to happen at almost any time and is one of the reasons why operation on six metres is so appealing.

Another method of predicting an opening, is to actually monitor the MUF as it moves higher in frequency. This can be achieved by listening to the 20 MHz portion between 30 and 50 MHz. This part of the spectrum is populated by a wide range of services all over the world. These include American utilities, for example emergency services, water and electricity companies, Russian radio telephone services etc etc. Most of these operate using FM. In addition various parts of the world still operate a Band 1 television service which is partly in this range; these can be identified as a sort of buzzing noise on the video frequency, to straightforward FM or AM voice on the audio frequency. By knowing what these are and where to find them, a good idea of the range and direction of an opening can be achieved. To give you an example, advance notice of an opening to the Caribbean was gained by monitoring the Jamaican Fire Service frequency just below 50 MHz. The equipment needed to monitor these frequencies can be anything from a general coverage receiver, to a converter ahead of your HF or indeed two metre rig. It is more usual though to use one of the many scanning receivers on the market. These are ideal for this purpose and are well worth the investment for the serious Six Metre DXer.

Until a few years ago, little commercial equipment had been available in the UK for use on six metres. The equipment that did exist was either imported from the USA or homebuilt. The release of six metres here has prompted most dealers to stock equipment for the band. For those of you with the cash, several commercial rigs either dedicated to six metres or multiband are now available.

Alternatively, something second-hand or homebrew is the answer. Equipment can cost from in excess of �1000 to less than �80; the cheap end of the market is taken by the homebuilt transverter; the two most popular being the G3WPO version marketed by Cirkit, and the Practical Wireless PW Meon. The Cirkit transverter needs a 28MHz transceiver to drive it, whereas the Meon can be configured for either a 28 or 144MHz IF. Both transverters provide between one half and one watt output, but even this power level is capable of working DX particularly by Sporadic E. The addition of an amplifier is a simple matter, so a complete transverter with a 25 watt PA can be built for around �100.

The transverter option may be the cheapest, but it does not mean that you will have to sacrifice anything in the way of performance. A well constructed and aligned transverter will hold it's own against any of it's more expensive counterparts.

Aerials for six come in various shapes and sizes. Since vertical polarisation has been allowed, a number of single and multi-band aerials including six metres have come on to the UK market. As all DX operation is achieved by reflection or refraction, then the problems of cross-polarisation common on two metres don't occur, in other words there is no way to tell what polarisation the received signal will have anyway so why worry. Typical aerial systems range from a wire dipole in the loft, to a five or six element beam outdoors. What you choose to use will of course depend upon your individual circumstances, but remember that useful results can be achieved with almost any system that resonates in the band.

A good performer at low cost is the HB9CV antenna for six, which is a light and fairly unobtrusive 2 element beam available at low cost. This is a considerable improvement over the simple wire dipole, and is also ideal for portable use. Remember that a high gain aerial will improve your reception capability, so it is better to run lower power to a larger antenna to improve the stations all-round performance rather than high power to, say a vertical.

May we remind you at this stage that the six metre band is now available to Novice Licencees. Even with the Novice power restrictions, it is possible to work all of the DX mentioned earlier.

Finally, any discussion about Six Metres would not be complete without mentioning the UK Six Metre Group. Formed in the early 1980s, the group is dedicated to promoting six metres internationally. It has an extensive beacon programme and has provided many of the beacons currently operating throughout the world. The group also sponsors Europe's premier six metre contest and has a comprehensive awards programme. A quarterly newsletter provides extensive news, reviews and technical data connected to six metres; it is professionally produced and carries articles by most of the worlds leading six metre operators.

[http://uksmg.org/content/images/speaker1.gif]<http://uksmg.org/content/audio/vk8gf.ra>Click the button to hear Hong Kong's VS6SIX beacon in Europe as heard in February 1992, soon we were all working VS6WV - if you could hear him underneath the video!

Now that you have read this and seen what the 'magic' band is about why not join the UKSMG<http://www.uksmg.org/applic.htm>?

We would like to thank Henk-PA2HJS, Frank-PA3BFM, and Ari-OH9NYW for their audio recordings.

--
António Matias

CT1FFU - CR5A

www.dxpatrol.com<http://www.dxpatrol.com>

QRV: HF, 6m, 4m,2m,70cm,23cm
SSB, CW, MGM
DX, EME, Contest,Sat.



--
Para mais informações/opções visite o site, e edite a sua conta:
http://groups.google.com/group/ct-comunicacoes-e-tecnologias?hl=en?hl=pt-PT
-------------- próxima parte ----------
Um anexo em HTML foi limpo...
URL: http://radio-amador.net/pipermail/cluster/attachments/20110511/bb74067c/attachment.html