Saturday, March 29, 2014

Surreal programming affected by weather, and explained by the Navy

It so happens I tend to be a night owl. Oftentimes wish it were not so, as it creates all kinds of obstructions.. most notable having to get up to go to work right around the time I'm finally ready to go to sleep..
Ahhh,.. but let me get to the point before I drift completely off the intended topic.

I like listening to Coast to Coast AM, don't particularly care who the host might be on any given night... and no, nothing about that surreal program has anything to do with  the topic I'm about to present, but it is what indirectly led me to where I am now.. So just bear with me a moment.

Almost every night around midnight, I reach over and turn on a portable Lifelong brand radio to 1290 AM  to listen to another night of Coast to Coast AM. Never have I experienced notable reception problems.. at least never this bad. Never, that is, until tonight. No matter where I move the radio or what angle it's positioned, the signal won't hold for more than a few sporadic seconds at a time, and the show is completely unlistenable.

What's causing this? Sunspots? The weather? Yeah it is raining tonight, but it's rained plenty of times without this much adverse affect. I pull up the weather report online..

Precipitation currently 60%, Humidity 99%, Wind 2 mph.  Hmmmmmm....

What of it? I don't know. So off I go exploring the net for an explanation about what the weather is actually doing to the reception of the signal, and eventually end up, in of all places, slap down in the middle of chapter 2 of a US Navy training manual in about Radio Wave Propagation..Page 2-34


Weather is an additional factor that affects the propagation of radio waves. In this section, we will explain how and to what extent the various weather phenomena affect wave propagation.

Wind, air temperature, and water content of the atmosphere can combine in many ways. Certain combinations can cause radio signals to be heard hundreds of miles beyond the ordinary range of radio communications. Conversely, a different combination of factors can cause such attenuation of the signal that it may not be heard even over a normally satisfactory path. Unfortunately, there are no hard and fast rules on the effects of weather on radio transmissions since the weather is extremely complex and subject to frequent change. We will, therefore, limit our discussion on the effects of weather on radio waves to general terms. . 


Calculating the effect of weather on radio wave propagation would be comparatively simple if there were no water or water vapor in the atmosphere. However, some form of water (vapor, liquid, or solid) is always present and must be considered in all calculations. Before we begin discussing the specific effects that individual forms of precipitation (rain, snow, fog) have on radio waves, you should understand that attenuation because of precipitation is generally proportionate to the frequency and wavelength of the radio wave. For example, rain has a pronounced effect on waves at microwave frequencies. However, rain hardly affects waves with long wavelengths (hf range and below). You can assume, then, that as the wavelength becomes shorter with increases in frequency, precipitation has an increasingly important attenuation effect on radio waves. Conversely, you can assume that as the wavelength becomes longer with decreases in frequency, precipitation has little attenuation effect.


Attenuation because of raindrops is greater than attenuation because of other forms of precipitation. Attenuation may be caused by absorption, in which the raindrop, acting as a poor dielectric, absorbs power from the radio wave and dissipates the power by heat loss or by scattering (fig. 2-24). Raindrops cause greater attenuation by scattering than by absorption at frequencies above 100 megahertz. At frequencies above 6 gigahertz, attenuation by raindrop scatter is even greater. 

 It continues on from there discussing fog, snow, and hail.. but that's where I stop reading; I had found my answer; It was the rains fault... or at least that is the conclusion I choose to rest upon to stop me from running after a wild goose all night.

Perhaps I didn't really find an answer, and even if I did, I didn't comprehend it deeply enough to recognize it. Still I did get to read a lot of interesting things along the way. It's a well written manual.. not that I read it all, but I did eventually find myself jumping to Chapter 1 to read a delightful introduction to the course:


Of the many technical subjects that naval personnel are expected to know, probably the one least susceptible to change is the theory of wave propagation. The basic principles that enable waves to be propagated (transmitted) through space are the same today as they were 70 years ago. 

One would think, then, that a thorough understanding of these principles is a relatively simple task. For the electrical engineer or the individual with a natural curiosity for the unknown, it is indeed a simple task. 
Most technicians, however, tend to view wave propagation as something complex and confusing, and would just as soon see this chapter completely disappear from training manuals. This attitude undoubtedly stems from the fact that wave propagation is an invisible force that cannot be detected by the sense of sight or touch. Understanding wave propagation requires the use of the imagination to visualize the associated concepts and how they are used in practical application. This manual was developed to help you visualize and understand those concepts. Through ample use of illustrations and a step-by-step transition from the simple to the complex, we will help you develop a better understanding of wave propagation. In this chapter, we will discuss propagation theory on an introductory level, without going into the technical details that concern the engineer. However, you must still use thought and imagination to understand the new ideas and concepts as they are presented.

You got to love whoever wrote that!

I'll try to refrain from ever writing another such loopy blog post as this one turned out to be. Sometimes, I just can't help myself. Well, gotta be up in 3 hours. I'm going to bed.


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