Microwaves (the actual radio waves) are between 1 mm and 30 cm long, and operate in a frequency range from 300 MHz to 300 GHz. Microwaves were first used in the 1930s, when British scientists discovered the application in a new technology called radar.

 In the 1950s, microwave radio was used extensively for long−distance telephone transmission. With the need to communicate over thousands of miles, the cost of stringing wires across the country was prohibitive. However, the equipment was both heavy and expensive. The radio equipment used vacuum tubes that were bulky as well as highly sensitive to heat. All of that changed dramatically when integrated circuits and transistors were used in the equipment. Now the equipment is not only lightweight, but also far more economical and easy to operate. In 1950, the typical microwave radio used 2,100 watts to generate three groups of radio channels (each group consists of 12 channels), yielding 36−voice−grade−channel capacity.

 Each voice grade channel operated at the standard 4 kHz. Today, equipment from many manufacturers (and Harris/Farinon, specifically) requires only 22 watts of output to generate 2,016 voice channels. Although there have been two orders of magnitude improvements in the quality of the voice transmission, the per−channel cost has plummeted from just over $1,000 to just under $37. This makes the transmission systems very attractive from a carrier's perspective. However, the use of private microwave radio has also blossomed over the years because of the cost and performance improvements.

What About Bandwidth?

Bandwidth is always a touchy subject. It can become a "never satisfied drain" on the corporate bottom line if due diligence is not practiced. There is a direct relationship to cost and total bandwidth. The more bandwidth needed, the greater the cost. Everyone would like as much bandwidth as possible, and at the same time wants it to be affordable. Many people make the mistake of buying more than they need, anticipating future growth. In this industry, prices keep falling as competition increases. If an organization needs an OC−3 (155 Mbps) today, then laying fiber is probably the most affordable solution. However, 155 Mbps microwave systems are available and the prices are constantly dropping, giving short−haul fiber a run for the money.
Conversely, if 10 Mbps Ethernet is the current rate of transmission, then this demand can be
immediately met. Additional bandwidth can be bought later. In two to three years, the costs will
plummet so that the new requirements can be met with incremental or marginal costs.
It's wiser to buy bandwidth as you need it and not before (there will be a small amount of
incremental add−on, but limited). In the future, there will be the following:

• More choices
• Increased providers
• Greater availability
• Lower costs




What should be done in the interim to satisfy the need? The answer is the following:

• Lease (dark) fiber instead of paying the cost of installation

• Lease services from the Incumbent Local Exchange Carrier (ILEC) or CLEC if sufficient
bandwidth is available
• Buy a wireless connection such as point−to−point microwave

Having too much bandwidth is possible. Having too much reliability is just the opposite.
Organizations lose significant amounts of money when the network connection is too slow, but far more when the link is down completely. One hour of network downtime can cost more than the profits and productivity achieved from a year of uptime. In this scenario, automatic backup is an absolute must. Buy the appropriate amount of bandwidth and make sure that the reliability is built in. Plan for the worst−case scenario! Consider an alternate backup plan. Use circuit−switched or packet−switched (frame−switched) alternative connections in case of an outage.

Prior to the 1970s, microwave was the most widely used wireless communications medium in the world. Microwave usage is making a comeback now with end users. Many user organizations were reluctant to experiment with microwave radio transmission due to misconceptions surrounding the technology as well as confusion between the "wireless" products. It is important to recognize that
the difference between one wireless device and another can be as different as fiber and copper wire. Both fiber and copper are "wired," but that is where the commonality ceases. The same is true between microwave and laser, spread spectrum, or cellular service. There are even differences between one type of microwave and another. The differences are due primarily to their respective operating frequencies. Some frequencies are good for distances of 30 or 40 miles and others can barely get you across an office park. Some can only support a couple of T1s or a single video channel and others go to 10 to 45 Mb.