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402-431-100 PRACTICES SECTION BELL SYSTEM Issue 1, July, 1947 Plont Series AT&TCo Standard

MICROWAVE ANTENNAS KS-5708 LIST 1 PERFORATED PARABOLIC DESCRIPTION

CONTENTS PAGE 2. CIRCUIT DESCRIPTION CAl 57" Antenna 1. GENERAL . 2.01 The layout of this antenna is shown in 2. CIRCUIT DESCRIPTION Figure 1, page 4. It has a wave guide feed at the focal point of the parabolic reflector and CAl 57" Parabolic Reflector Antenna sprays the electromagnetic energy at it in the form of spherical waves. The waves in turn are 3. EQUIPMENT FEATURES . reflected outward as essentially plane waves as a result of the contour. The narrowness of beam CAl 57" Parabolic Reflector Antenna depends upon the diameter of the reflector, which in this case is 57 inches. This develops a 4. TRANSMISSION CHARACTERISTICS . 2 beam width of about 3.5 degrees between 3 db points as shown in the pattern in CAl 57" Parabolic Reflector Antenna 2 Figure 2, page 5. The gain of the antenna at 4100 me is 31 db over a half-wave dipole; the 5. PHOTOGRAPH AND FIGURES 2 gain vs. characteristic is shown in Figure 3, page 6. The back-to-hack pickup by a like antenna is about 75 db down. _'"_]. GENERAL

1.01 This section pertains to the 57" parabolic 3. EQUIPMENT FEATURES (KS-5708). Circuit and reflector antenna CAl 57" Parabolic Reflector Antenna equipment data are included, as well as trans­ mission characteristics. Related photographs 3.01 The parabolic dish is a perforated alumi- and drawings are also included. num sheet 57-1/4" in diameter with a steel supporting ring on the extreme circum­ ference and a supporting ring casting of alumi­ are suitable 1.02 Parabolic reflector antennas num toward the center. An isometric drawing for use as transmitting or receiving an­ of the assembly is shown in Figure 1. The focal tennas for line-of-sight broad band distance of the parabolic dish is 19 inches. The systems of the portable pick-up variety. feed is a tapered 2-inch by l-inch brass wave In general, parabolic reflector antennas have guide with a flange for connection to 2-inch by good forward gain and fair side and back lobe l-inch wave guide. The midband frequency of suppression. Hence they lend themselves to use this antenna is approximately 4050 megacycles. on paths of moderate length where the highest The center of the beam is adjustable to either degree of directivity is not required to avoid 60" or 35" above the floor line. interference. 3.02 The parabolic dish and casting are sup- ported on a floor frame which when par­ 1.03 The practical working range of the de- tially fastened permits antenna adjustments of sign described in this section is from 3890 ±5 degrees in elevation and +3 degrees tra­ to 4200 megacycles; however, parabolic reflec­ verse. The weight of the parabolic dish, casting tor antennas may readily be built for other and is 55 lbs. and the floor support microwave . weighs 45 lbs. • ©American Telephone and Telegraph Company, 1947 Printed in U.S.A. Page 1 SECTION 402-431-100

4. TRANSMISSION CHARACTERISTICS (8} Figures CAl 57" Parabolic Reflector Antenna DESIGNATION SUBJECT PAGE NUMBER 4.01 Transmission characteristics for the 57" Figure 1 Parabolic 4 parabolic reflector antenna are as follows: Reflector An- (a) Gain in forward 31 db over half-wave tenna Assem- direction dipole at 4100 MC bly-57" Di- (b) Beam width 3.5 degrees (between ameter (horizontal) 3 db points) Figure 2 Directivity 5 (c) Back-to-back About 75 db Pattern for ratio (to like 57" Parabolic antenna) Antenna at 4300 MC 5. PHOTOGRAPH AND FIGURES CAl Photographs Figure 3 Gain-Frequency 6 DESIGNATION SUBJECT PAGE NUMBER Characteristics Photograph A 57" Parabolic 3 of 57" Para- Reflector bolic Reflector Antenna Antenna

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Page 2 ISS 1, SECTION 402-431-100

Photo A- Parabolic Reflector Antenna Assembly Reflector Diameter-57" (Wave Guide Feed Oriented for Vertical )

Page 3 ISS 1I SECTION 402-431-1 00

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Fig. 1 -Parabolic Reflector Antenna Assembly 57" Diameter

Page 4 L ISS 1 , SECTION 402-431 -1 00

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Fig. 2 - Directivity Pattern for 57" Parabolic Reflector Antenna at 4300 MC

Page 5 ISS 1, SECTION 402-431-100

31

30

42.00 4300 3800 3900 4000 4100

Frequency in Megacycles

Fig. 3- Gain-Frequency Characteristic of 57" Parabolic Reflector Antenna

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