Hugh:
I have comments to the communications section of Redoubting Thomas’ article. Communication is the process of moving information from one place to another. In a TEOTWAWKI situation, there will not be just one specific communication need, there will be several. You will want to communicate over short, medium, and long distances. Some communications needs will be one way. Some will be two ways. Differing needs require differing means to achieve differing objectives. In my opinion, the CB radio, for very many technical reasons, is a poor solution for many, if not most, of these needs.
The author emphasizes that CB requires no license. Technically, this statement is untrue. While the FCC does not require an individual station license, the legal user of a CB is licensed collectively as an eligible licensee, i.e., a U.S. citizen. The FCC does regulate the use and specifications of CB radios in the U.S. In a WROL situation, having or not having a license means nothing.
The author states that a CB radio “can do up to 12 watts on SSB (4 on AM).” Then he goes on to discuss the relative merits of SSB versus AM operation, suggesting that SSB is inherently better because of wasted power in the carrier and one sideband. In reality, the 12 watts for SSB is peak envelope power and the 4 watts for AM is average carrier power. These two types of power– peak envelope power and average carrier power– describe two very different things. The fact is that 12 watts PEP and 4 watts average carrier power are essentially the same amount of usable signal power at the antenna and that either type of signal travels essentially the same distance given the same environment.
The description of how a modulating signal applied to a carrier generates sidebands is generally correct in a simple way, however, the primary effect is that generating a SSB signal is more efficient in terms of the information content, but generating a SSB signal requires more complicated circuitry and increases the cost of the transmitter and receiver as compared to an AM radio.
The author talks about NVIS versus omni antennas and increasing communications distance. The concept of NVIS (Near Vertical Incidence Skywave) antennas is about transmitting a signal nearly straight up so that the signal reflects back down, off of the F2 layer, within roughly 200 to 600 miles of the transmitter. Unfortunately, this effect starts to lessen dramatically above roughly 10 MHZ. At CB frequencies near 27 MHz, there is no NVIS effect. Transmission of NVIS signals at near CB frequencies exceeds the critical angle for reflection and pass right through the ionosphere into outer space. Omni, meaning omnidirectional, antennas will generally provide the least distance in any particular direction. You can increase distance, in one particular direction, by choosing a beam antenna over a typical omnidirectional antenna. There are many antenna designs with greatly differing characteristics in gain and directivity. Which one to choose depends on the purpose of the communication system.
The author mentions sunspots, the ionosphere, and the Creator. The Creator has given us the 11-year sunspot cycle. We are currently about half way down from the peak of the current sunspot cycle. This means that for about the next ten years, long distance communications on CB frequencies will be virtually nonexistant. Most CB long distance communications is by means of sporadic E skip. You might have heard the term “talking skip”. This is where the term comes from. The “E” in sporadic E skip refers to the E layer of the ionosphere. The E layer is created daily by the sun and disappears at night. It also has some seasonal effects. The word sporadic means that increased densities in the E layer able to support long distance CB communications occur only sporadically. A means of communication that depends on sporadic occurrences and changes with time of day and time of the season is not very predictable or reliable. CB radio is probably best used for short distance communication in a local area. For this use, it is a disadvantage that residents of the east coast can hear your communications between neighbors in Idaho.
My point in mentioning all of this detail is twofold. First, because communications needs vary greatly, communications solutions also vary greatly and can be much more complicated to implement in a real TEOTWAWKI situation. Preparing long-term communications plans requires knowledge of radio equipment, antennas, radio wave propagation, and an understanding of the communications requirements and how to combine these factors to achieve the desired results. Second, I would highly suggest that anyone looking to provide communications in the long term either spend the time and effort required to get the knowledge and acquire the skills necessary or find someone who has the knowledge and skills to help them with their plans.
– an Extra Class Ham