Propagation´s Radio Weather 50 MHZ Activity
6 Meter Ham Band Activity and the Propagation Modes Driving It
The most popular way of getting information on 6-meter ham band activity is by monitoring DX clusters. But that's not the only way!
Besides monitoring six-meter activity, and looking for 6-meter band openings, the second purpose of this article is to help you understand how each different propagation mode helps your 50 MHz signal along. With this knowledge, you will eventually be able to anticipate favorable conditions!
But, first, let's have a look at the resources that you can tap into to see what's going on on six.
6 Meter Ham Band Activity Web Resources
6 Meter DX Map by EA6VQ
In our view, this is probably the best 50 MHz propagation map on the Web. It immediately shows what the possibilities are of contacting other ham radio operators on six meters.
Quoting from the website:
"It aims to provide a detailed but comprehensive view of the propagation conditions in real time".
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We strongly recommend reading the user manual. It's an indispensable tutorial to enable you to get the most out of this sophisticated resource.
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We also strongly recommend reading the online FAQ page. It's comprehensive and very informative!
You can extract an amazing amount of useful information on 6-meter ham band activity from the map. It's extensively configurable. You can make it display only what you want to know.
Here are two of the countless useful features:
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-The links between QSO contacts are color-coded so that you can immediately see which propagation mode was contributing to the establishment of any given QSO.
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The call signs are also color-coded to show which communication mode was involved in the QSO being shown on the map.
Almost addictive!
The UKSMG Map of 50 MHz activity spotted in the last hour (http://uksmg.org/dxcluster/NewMap/index.php) is somewhat similar. It also displays color-coded lines that identify the propagation mode in action for any given QSO, when it is reported, of course. The spot data for that map is provided by GB7DJK.
6 Meter Ham Band Activity Web Resources
Ionized Layer 'D'
During the day, the ionized layer 'Mostly hinders ionospheric propagation of radio waves. It is the ionized layer closest to the earth's surface. It is located between 60 km and 100 km (37-62 miles) above the earth. In the daytime, it forms under the sun's intense UV radiation and constitutes a barrier preventing radio signals in the 40-meter, 80-meter, and 160-meter bands from getting far and from being heard in the intense atmospheric noise. Meanwhile, signals 10 MHz and above can get through to reach the ionized layers above and make their way beyond the horizon.
Another way of finding out about 6-meter band conditions is to use a map of the WSPR signals reported. (http://wsprnet.org/drupal/wsprnet/map).
For those of you who might not be familiar with WSPR, please visit:
http://physics.princeton.edu/pulsar/k1jt/wspr.html
To display the 6-meter ham band activity on the map you must set a minimum of parameters (located below the map):
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Set the band to 6m (I think the default is 30m)
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Set desired period (default is 1 hour)
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Day/Night overlay (check the box if you want to display it)
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Go back to just below the map and click 'Update'.
Note that the map uses a Google service for development purposes only... which might be taken down, or become a paid subscription service anytime.
If you see "For development purposes only" stamped in light gray all over the map, then the Google services map display, it depends on, may be living on borrowed time. Meanwhile, enjoy it while it’s available.
50 MHz DX Clusters
Another way of finding out about 6-meter band conditions is to use a map of the WSPR signals reported. (http://wsprnet.org/drupal/wsprnet/map).
For those of you who might not be familiar with WSPR, please visit:
http://physics.princeton.edu/pulsar/k1jt/wspr.html
To display the 6-meter ham band activity on the map you must set a minimum of parameters (located below the map):
-
Set the band to 6m (I think the default is 30m)
-
Set desired period (default is 1 hour)
-
Day/Night overlay (check the box if you want to display it)
-
Go back to just below the map and click 'Update'.
Note that the map uses a Google service for development purposes only... which might be taken down, or become a paid subscription service anytime.
If you see "For development purposes only" stamped in light gray all over the map, then the Google services map display, it depends on, may be living on borrowed time. Meanwhile, enjoy it while it’s available.
50 MHz DX Clusters
BEACONS
One of the best, nearly passive ways of monitoring 6-meter ham band activity in real-time is to listen for beacons of the 50.000 MHz to 50.499 MHz band of frequencies (52.342 to 52.490 in Australia and New Zealand).
When you hear one or more of the many 50 MHz beacons, it provides an early warning of favorable propagation conditions between you and the location of the beacon.
I just set my IC-7300 to continuously scan for CW signals between 50.000 MHz and 50.500 MHz until it pauses on a CW signal. When it does, the squelch opens and I can stop the scan to listen. If it's a beacon, I can get its call sign and I then look it up in G3USF's list for more information on it:
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location
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grid square
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transmitting power
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type of antenna
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radiation pattern (omnidirectional or directional)
The Propagation Modes
Behind 6 Meter Ham Band Activity
VHF (50 MHz and 144 MHz) radio signals can travel way beyond the horizon thanks to various propagation modes. Some are well known while others are not. We will name them and briefly describe them in a moment.
Fans of the six-meter (50 MHz) frequency band dub it the "magic band". It can often be frustratingly inactive, but it can also suddenly become alive, usually for a short time, causing an intense flurry of activity... before quietly going to sleep again.
During such "magical" moments, I would compare the sudden furious 6 meter ham band activity to a bank of piranhas rushing on a duck that had the unfortunate idea of landing on the surface of a calm-looking river. The 50 MHz frequency band can then suddenly start to boil over with activity for a few minutes (rarely a few hours).
It's both fascinating and mind-boggling to witness such an event, not to mention the adrenaline rush that galvanizes us into action, in an attempt to complete as many QSOs as possible during these brief moments!
The Layer 'E' of the Ionosphere
More often than not, the propagation of 50 MHz radio waves will depend on the ionized layer 'E' of the ionosphere, which is about 20 km thick and its base is about 100 km above ground level.
The 'E' layer is present mainly during the day, from dawn to dusk, and is responsible for most of the 6-meter ham band activity.
The 50 MHz signals, reaching the 'E' layer with a small angle of incidence, will be reflected towards the ground and will thus reach great distances from their point of origin.
Like the other ionized layers in the ionosphere, the ionization intensity depends entirely on the level of activity of the sun during the solar cycle.
Sporadic 'E' (Es) Events
In addition, during summer daytime, in mid-latitudes, mainly from May to July, stealthy "densely ionized" clouds appear briefly in the 'E' layer, usually for a few tens of minutes. That's what is called sporadic propagation 'E' ('Es'). This phenomenon can sometimes occur at night too!Little is known about the causes behind the formation of these "clouds" of intense ionization. There are many theories, but ... the important thing is that they appear without warning and that we can take advantage of them.Our ability to catch ES events depends on close monitoring of 6-meter ham band activity. My favorite way is to listen to my IC-7300 as it scans the lower 500 kHz of the six-meter band, while I do something else in the shack or on the workbench.During the May-July summer period, when these sporadic 'E' events usually occur, it is possible to establish contacts over distances varying from 600 km to 2300 km, even at low power with simple (horizontally polarized) antennas. However, it's best to use the CW mode or a digital mode like FT8 with Es propagation because deep QSB is often in play.
The Auroras
Auroras (northern lights or Aurora Borealis in the northern hemisphere -aurora australis in the southern hemisphere) can sometimes contribute to VHF radio propagation and 6-meter ham band activity.
Solar wind hits earth's magnetosphere producing an aurora. (Source: https://www.youtube.com/watch?v=ziRKy6rNpR8)
Here is a detailed description of the creation of the northern lights on YouTube.
Valley ducting of VHF radio waves.
The border (transition zone) - between warm drier air resting on cool more humid air at the bottom of a valley - acts as a refraction zone and prevents signals from escaping out of the valley.
Such an inversion forms a "conduit", at the bottom of the valley, which traps the VHF signals and forces them to travel along a "corridor" also called "duct" or "tunnel".
This "duct" will form a few hours after sunset and will dissipate shortly after dawn, under the action of the sun. This thermal "conduit" will be at its most effective an hour or two before dawn.
The VHF signals which are emitted within this "conduit" can reach hundreds of kilometers, as long as the "conduit" remains intact, thus contributing additional 6 meter ham band activity.
An Example:
In Québec, the city of Montréal is located in the St. Lawrence River valley. This valley originates in the lower Great Lakes of Ontario and Erie, located to the southwest.
I was sometimes able to successfully communicate, in SSB and CW, with about 20 watts on 50 MHz, from Montréal, Quebec, late on a clear night in August, with ham radio operators located on the western shores of Lake Ontario, some 600 km upstream... and my antenna was a simple folded dipole oriented north-south, up at 30 feet, therefore radiating broadside toward the west and east.
Tropospheric Ducting Forecast
Fortunately, William R. Hepburn has developed a method of forecasting tropospheric ducting for up to 6 days ahead. It is a very good and 'unique' VHF tropospheric propagation prediction tool. The Hepburn Tropo Index (HTI) forecast is available for most regions of the globe.
You can select the region you want a tropo forecast for by using the drop-down menu labeled "Select Region...", located in the top left corner of the page located at: http://www.dxinfocentre.com/tropo.html .
TheHepburn Tropo Index(HTI) is explained in detail here: http://www.dxinfocentre.com/propagation/hti.htm
(use text only)
Finally, you will find an excellent explanation of the various tropospheric propagation modes here: http://www.dxinfocentre.com/propagation/tr-modes.htm
Warm Front Refraction
Another 50 MHz propagation zone can form ahead of a warm front.
The imminent arrival of a warm front will sometimes, under certain conditions, offer an opportunity for a temperature inversion in the lower levels of the atmosphere, which will be favorable to tropospheric VHF propagation... and more 6 meter ham band activity.
A temperature and humidity inversion will sometimes be sufficiently well defined, a few hours before the arrival of a warm front, mostly...
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at night,
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in spring and fall,
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under cloudless skies,
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when relatively warm and dry air,
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overcomes relatively cooler, more humid air.
Radio operators who are then located in the 50 MHz radio wave propagation zone (VHF) located in relatively colder moist air - position represented by the capital letter the cold air below the frontal zone - just under and along the warm front (transition zone between cold air and hot air)...
... will be able to take advantage of the refraction action of the frontal transition zone which will prevent the VHF signals from escaping into space and, thus, will guide them along for hundreds of kilometers under the frontal zone.