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security measures which gave the various bands letter designations during this conflict brought the name into use. At any rate, it is a good name for the spectrum which, as we proceed to examine it, will be seen to include wavelengths of some frequencies we can use as amateurs which are hardly as long as the word microwave itself.

Let us examine how the Federal Communications Commission has assigned band nomenclatures to the radio spectrum and also how microwave equipment manufacturers have retained the WWi I designations.

The FCC has assigned band numbers and lettered designations as nomenclature for all of the electromagnetic spectrum. The frequency allocations that are assigned to the ham bands are known to us by their designations, VHF, UHF, VLF and others. {See Table 1J

The designations in Table 1 are found in the Rules and Regulations part of many of the commercial hcense examination question -and-answer books. Notice that the way they are grouped falls in line with the metric system, and that if the metric equation is worked out to become meters in wavelength, it falls m decades. Either way, it's easy to remember after a slight bit of study.

Further examination of the other tables may open your eyes to several facts about the bands that we occupy and rarely think about in terms of how they are located in the radio spectrum.

Table 2 shows how the HF spectrum adds up to the number of megacycles that we as amateurs occupy. When one examines the dial of the station HF receiver, the number of bands and the spread of themi over the dial make it look vast. The frequency ranges are in very small steps from 160 to 10 meters in most receivers, but when the total number of amateur frequencies is added up it's only 3.5 MHz total coverage out of thirty—a little more than ten percent,

Some of the small nations that will attend the World Administrative Radio Conference (WARC) are of the opinion that, although they have a very small population in the vast high frequency seaH they now will need more. When they band together with their 1 vote-per-nation, they are going to be a formidable group, looking at our 10% as something they want —and may get.

Why bring this up? Let's look further at the number of megahertz we have available in the high frequencies. i he total up to the end of VHF assignments, that stop at 1 V* meters, is 20.5 MHz. If we go on up into the microwaves, the total number of gigahertz that we have is 23,290 [see Table 2). Out of this, very little is used by amateurs. The J/i-meter band is used quite a bit for repeaters, and 12% MHz is really catching on these days as are many of the frequencies up through 10 GHz, but not enough. It looks as if we could lose a lot of spectrum simply because we do not lay claim to it by enough use. These frequencies are very attractive to the 40 or more nations who will certainly exercise their combined single votes.

When you look at Table 2 again, you can see that the total number of gigahertz, not megacycles, is listed at 23.290, and the last assignment, which starts at 300 GHz, isn't listed in

Band 4. ■ Band 5.. Band 6.. Band 7,, Band 6.. Band 9-. Band 10. Band 11.

, VLF Very Low Frequencies Below 30 kHz

, LF Low Frequency 30 to 300 kHz

, MF Medium Frequency 300 to 3000 kHz

. HF High Frequency 3 to 30 MHz

. VHF Very High Frequency 30 to 300 MHz

. UHF Ultra High Frequency 300 to 3000 MHz

. SHF Super High Frequency 3 to 30 GHz

. EHF Extremely High Frequency... 30 to 300 GHz

Table 1. Nomenclature of frequencies, t the table; that gives us all above that to play in.

Well, I can hear some of the groans and moans from those who will say, "So what? How in the heck can we get up that high?" I'll tell you: These frequencies are in use commonly by commercial users right up to and well beyond the highest assignment,

The microwave spectrum is made up of bands, referred to popularly by designations such as "S"~band or "X"-band. An examination of Table 3 shows how these bands are designated today. The table was taken from a manufacturer's list of waveguides and waveguide components such as flanges and covers, and, later on, the Electronic Industries Association (EIA) gave additional references. There are many others, but those listed are the most popularly used. Table 3 designations are useful to amateurs who are scrounging the surplus market for components for microwave construction. Many of the components are marked with waveguide designations that may confuse them, however. For example, a waveguide sec

160 . . . 10 meters

3.5 MHz

160 .,. 1Va meters,.

..20.5 MHz,

420-450 MHz

_____30 MHz

1215-1300 MHz. #

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