The word professional is regularly misused today, and its use in the title of this chapter may appear to the outsider to be yet one more abuse. However, the work of a radar technician truly falls within proper definitions of the term. Some work is called a 'trade' and some is called a 'profession'. A 'trade' is defined as skilled work, but is differentiated from a profession by dictionary definitions. Definitions for 'profession' include such concepts as 'involving mental rather than manual work' Generally, 'trade' would describe such occupations as plumbers, electricians, welders, mechanics, and machinists where skill in performing tasks is more necessary than extensive knowledge. 'Profession' would describe such occupations as doctors, nurses, dentists, chemists, physicists, engineers, attorneys, etc. A Webster's Dictionary definition of the word 'technician' is 'one versed in the technicalities of some subject, specifically, an artist, writer, musician, etc. who has great technical skill or knowledge. The 'knowledge' part of the general definition of 'technician' places it in the 'professions' category. A 'profession' may require certain manual skills, but it is characterized principally by formal, academic, or scientific knowledge, and by a requirement to arrive at conclusions through application of that knowledge. The radar technician's job most certainly falls within that definition. He must be able to correctly theorize the source of a problem, even when he cannot see it. He must be able to document his actions in a manner adequate to allow readers to unquestionably understand him; this requires the correct and accurate use of accepted technical and scientific terms and definitions. He must also be able to speak of technical and scientific matters with the same precise, accurate, and correct use of terms and definitions, as problem solving and correction may often involve telephone communication with other technicians in locations perhaps hundreds of miles away, or even more.

This chapter is a very basic introduction to the principle of pulsed radar. Obviously, getting a beginning concept of the main principle is one objective. Another is to introduce many terms commonly used in the radar language. Those terms which are the most essential to remember are printed in bold italics to assist you. A transmitter emits a burst of RF energy, and objects in its path will reflect the pulse back to the transmitting antenna as an echo. A steering device, called a duplexer, allows the transmitter burst to go to the antenna without damaging the receiver, and then isolates the transmitter during a listening time. The listening time is usually called live time. During live time, the echoes from any objects, called targets, are routed into the receiver.

The intent of this chapter is to introduce the reader to the general configuration of FAA radar installations. The FAA radar network contains a wide variety of systems: Airport Surveillance Radar (ASR), Air Route Surveillance Radar (ARSR), Airport Surface Detection Equipment (ASDE), Precision Approach Radar (PAR) (use has been discontinued in favor of instrument landing systems (ILS)), and Terminal Doppler Weather Radar (TDWR). Until deployment of the ASR-9, ASR-11, and ARSR-4, the ASR and ARSR, up to the video outputs, were very similar. This chapter will begin with a hypothetical, generic, synthesis systems as illustrated in Figure 6-1. This system will roughly resemble the ASR-8, ARSR-3, FPS-20, FPS-64, 65, 66, and 67. The system could also be converted to a magnetron system with the addition of coho phase-locking circuitry and automatic frequency control, and would then resemble the ASR-4, 5, 6, and 7, and the ARSR-1 and -2. Additionally, the USAF uses a modified version of the ASR-8 containing a magnetron and the necessary additions; in this system, the magnetron tuning is driven by the afc.

The author of this book makes only a limited claim to the originality of this chapter. It has been rewritten from Chapter 10 of US Department of the Air Force Manual 52-8, entitled Radar Circuit Analysis, published June 30, 1951. The entire chapter has been retyped, edited, supplemented, and reformatted. Some of this was done to more closely conform to latter-day technical writing standards, some to add more current information, some for clarification, and some to make it more closely resemble the style of the other chapters of this book. Most importantly, no information has been deleted or diluted, and useful information has been added. All the illustrations have been retouched or redrawn, and all the labeling in the illustrations has been retyped.

The fundamentals of common radar-transmitter hardware were addressed in preceding chapters. This chapter will deal in greater detail with several aspects of the pulsed radar transmitter. One topic will be the origin and composition of the emitted energy, a wide spectrum of frequencies. Another subject is the modulator, which will apply a high-voltage pulse to a third area of interest, the final power amplifier, which may be a magnetron, a klystron power amplifier tube, a traveling wave tube (twt), or an amplitron, also called a cross-field amplifier (CFA). There are still other means to transmit the radar burst. A major component in the modulator is the pulse forming network, an artificial transmission line; considerable discussion of this device will be contained in this chapter.

When this author entered the radar field in 1955, moving target indicator (MTI) systems had been in existence for less than 10 years and were still viewed as new. The non-MTI AN/MPN-1 was still the world's most extensively used air traffic control radar. Of all radar subject material, technicians and engineers in 1955 saw MTI as the greatest mental challenge. With that challenge to his senses of responsibility and competence, the author has devoted the years since 1955 to learning about, writing, and teaching MTI theory. The approach in this chapter is purely his own, and represents years of work and study.

There have been other systems called moving target detectors and the term could lead to confusion to some experienced technicians unfamiliar with air traffic control radar. MTI, discussed in previous chapters, is an abbreviation for moving target indicator, a broad class of radar systems which indicate moving targets. An FAA MTD system, the system type hereafter simply called MTD, is within the broader class of MTI radar systems, and may be called an MTI system in some literature.