6

The D region does not affect all HF (3 MHz to 30 MHz) in the same way. For low frequencies, 2 to 4 MHz, the D region absorbs most signals during the sunlight times of the day. However, somewhere around the 3.5 to 4.5 MHz zone, the absorption starts to fall off as frequency is increased and these signals will penetrate the D region and reach the E region ...


6

Solar radiation ionizes the atmospheric gas, creating a plasma with free electrons. The density of these free electrons varies by height, time of day, and solar conditions. Because the electrons are free to move in the plasma, they will be displaced by an electromagnetic wave. If you want a rigorous mathematical treatment, The University of Toronto has a ...


5

Some googling for "ionosonde operation" reveals some applications (for example) to the FCC to operate under 47 C.F.R. §§ 5.3(c) and (e) which details that "Stations operating in the Experimental Radio Service will be permitted to conduct the following type of operations". So it seems that ionosondes in the US are governed by the FCC rules ...


3

There is also gray-line propagation, where signals can travel around the world at the circular dusk/dawn annulus. In that region, it is neither totally dark nor totally light. Long-Path QSOs are usually made following the path of this grayline (shown below). However, QSOs via the shortest path is more common than long-path (which has greater attenuation). ...


3

In an effort to find some hard data, I wrote to Dr Carl Luetzelschwab, K9LA. Carl responds: "The main reason is because we've basically been under solar minimum conditions for two years - and it looks like it's going to continue. We were spoiled by [shorter - Ed.] solar minimum durations prior to the minimum between Cycle 23 and 24." The graph Carl ...


2

The Band Activity chart at DX Heat is a good way to evaluate propagation from the standpoint of "who is working whom, right now." Combining the color coded activity depiction with your general knowledge of when bands are more likely to be open can guide you as to what bands are opening and which are closing. The filtering tools allow you to target specific ...


2

Quick and easy propagation forecast tools are at VOACAP Online http://www.voacap.com/prediction.html and http://www.voacap.com/coverage.html for area coverage. Required are the transmitter and receiver positions, transmitter power, mode, antenna types, date and sunspot number. It does not consider the effects of geomagnetic ionospheric disturbances. The ...


2

Calculating the angle of an incoming signal traveling via skywave is not nearly so straight forward as you might presume, and there are two primary reasons. The ionosphere is highly variable, and also exists not as a single impermeable layer, but rather a diffuse region several hundred kilometers thick. At any given moment, two signals of significantly ...


2

The ionosphere contains freely moving charged particles that act like a conducting "plate". When a radio wave traveling up reaches the ionosphere, the electric field of the wave starts to move the electrons. This movement that happens at the RF frequency acts like a current and the current acts a bit like an antenna creating its own wave that is now ...


2

With your project, is it necessary to always have the ability to communicate? Or can you batch up your data and wait for the conditions to be suitable and transmit back a batch of data? A little more information about your project and the type of data you wish to transmit may be helpful in answering this question (or even determining if amateur radio is ...


2

As a (fairly) regular member of the Worked All Britain net on 40m, the foF2 (I use the Chiltern Ionogram) critical frequency is one that I watch carefully, as it gives a pretty reasonable indication as to whether inter-G contact (for the WAB squares) is possible. Given that Chiltern can be temperamental, I do not rely on it, but it is certainly worth ...


1

It's pretty clear that we've reached the ~10.7-year solar cycle minimum in the midst of a low part of the ~87-year Gleissberg Cycle. See this explanation from Wikipedia. Occam's Razor points toward this relatively simple (though unfortunate for us hams) scientific explanation rather than other explanations. As usual, some hams are responding to this ...


1

Just wanted to post an answer so that this question wouldn't show up in an unanswered search result.I was using the wrong figures in my calculation. The altitude of the first F layer according to a Wikipedia article here is 150 km (93 mi). Using the correct figure gives me and incoming angle of 12° for a flat plane; subtracting half the angle between here ...


1

The DXLab Suite includes PropView, a convenient front-end to VOACAP, which makes current and near-term propagation predictions. PropView works in conjunction with the other components of the DXLab Suite, so it works best when you use DXLab for all of your logging and operating functions. You can download N6BV's Propagation Prediction Files with the purchase ...


1

Here is a useful site for both long-term (monthly) and near-term propagation conditions. http://propagation.hfradio.org/ For VHF and UHF skip conditions (just in case you are interested) try here: http://www.dxinfocentre.com/tropo.html


1

If you want to get a more automated prediction, look for propagation prediction software (many available on the 'net) and plug in the data. Of course, it's still useful to know the basics, such as how the ionosphere works (see ARRL handbook), to understand what the programs do. And very important: Even if you take into account all of the data you have ...


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