Six metres (50Mhz) The magic band
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.
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.
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.
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.
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 Licensees. 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.
Written by Trevor, G3ZYY
Visit the
UK Six Metre Group website...
|
