FAA-NA-77-39 Test and Evaluation of Air Ground Comm Antennas.pdf

a.rt II. FAal!IA-71,39 llflC l~ ""

· ~ JUI. Iflli;itT!iJIUi~i

/?/ TEST AND EVALUATION OF AIR/GROUND

<1,. .. COMMUNICATIONS ANTENNAS

r .:. .

James J. Coyle

JUNE 1978 ·

FINAL REPORT

Document is available to the U.S. public through the National Technical Information Service, Springfield, Virginia 22161.

Prepared for

U.S. DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION

Systems Research & Development Service Was~ington, D.C. 205!1)

NOTICE

The United States Government does not endorse products or manufacturers. Trade or manufacturer.'s names appear herein solely because they are considered essential to the object of this report.

Technical Report Documentation Page

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

FAA-NA-77-39

4. Title and Subtitle 5. Report Dote

TEST AND EVALUATION OF AIR/GROUND COMMUNICATIONS

ANTENNAS 6. Performing Organization Code

8. Performing Organization Report No.

7. Author1 s)

James J. Coyle FAA-NA-77-39

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

Federal Aviation Administration National Aviation Facilities Experimental Center 11. Contract or Grant No.

Atlantic City, New Jersey 08232 062-221-100

13. Type of Report and Period Covered

12. Sponsoring Agency Name and Address u.s. Department of Transportation Final Federal Aviation Administration January-December 1977 Systems Research and Development Service 14. Sponsoring Agency Code

\.Jashington, D.C. 20590

15. Supplementary Notes

1 ~. Abstract

This report presents data from the evaluation and analysis of a select group of very high frequency (VHF) and ultrahigh frequency (UHF) Air/Ground (A/G) communi-cation antennas. Antenna patterns, gain, and voltage standing wave ratio measure-ments were made at the National Aviation Facilities Experimental Center (NAFEC) antenna range on both Federal Aviation Administration (FAA) specified and commer-cially available off-the-shelf antennas. These antenna data show that improved A/G communications coverage can be obtained with some of the commercially available antennas.

17. Key Words 18. Distribution Statement

Air Traffic Control Communications Air/Ground Communications VHF Communications Antennas UHF Communications Antennas

19. Security Classil. {of this report) 20. Security Clossif. (of this page) 21. No. of Pages 22. Price

Unclassified Unclassified 123 Form DOT F 1700.7 (8-721 Reproduction of completed page authorized

Symbol in It yd mi in2 lt2 mi2 oz lb tsp Tbsp fl oz c pt qt gal ,,a ydJ

OF

Approximate Conversions to Metric Measures

When You Know inches feet yards miles square inches square feet square yards square mites acre$ ounces pounds short tons

(20()(1 lb) teaspoons tablespoons fluid ounces cups pints quarts gallons cubic feet cubic yards

Multiply by

LENGTH

'2.5 0.9 1.6

AREA

6.5 0.09 0.8 2,6 0.4

MASS (weight)

0.4&

0.9

VOLUME

1& 0.24 0.47 0.95 3.8 0.03 0.76

TEMPERATURE (exact)

Fahrenheit temperature

5/9 (after subtracting 32)

To Find centimeters centimeters meters kilometers square centimeters square meters square meters square kilometers hectares grams kilograms tonnes mill liters milllitc-rc;

mill liters titers hters liters liters cubic meters cubic meters

Celsius temperature

Symbol em em km cm2 m2 km2 ha kg ml ml ml

I

I mJ m3

"c

~or otl\er exa.Cl anrl mort> dNaded tl'lblt1S, S<!e NBS f>,,itJI. :?&;, S2 ,2!:1, $0 Ci:H<llng ClJJ 0:28G.

METRIC CONVERSION FACTORS

5' g.

E

::l

!:.1 e:::

Symbol mm em m km crrf m2 km2 no kg ml I

I m3 ml

"c

Approximate Conversions hom Metric Measures

When You Know millimetefs centimeters meters meters k i IOTleters

Multiply by

LENGTH

0.04 0.4 3.3 1.1 0.6

AREA

square centimeters 0.16 square meters 1 ~2 square kilometers 0.4 hectares !10.000 m2) 2.5

MASS {weight) grams 0.035 kilograms 2.2 tonoes (1000 kg) 1.1 milliliters liters liters, liters

· cubic ·meters cubic meters

VOLUME

0.03 2.1 1.06 0.26

1.3

TEMPERATURE {exact)

Ceisius temperature

9/5 (thefl add 321

°F 32 98.6

To Find inches inches feet yards miles square inches square yards square miles acres ounces pounds short tons fluid ounces pints quarts gallons cubic feet cubic yards fahrenheit temperature

"F

-4~ I I I ~ I I 11410 I I I 610 I ~ I 1~0 I I I 1?0' I I 2~ ·I I I f 1 f I I i I I

-40 -20 0 ZO 40 60 80 lOt> °C 31 °C lf#'\ otl'?tt • . ., Symbol in in It yd mi in2 yd2 mi2 oz lb fl oz pt qt gal ft3 yd3

OF

PREFACE

The author gratefully acknowledges the contributions and technical assistance provided by Norman Beauregard, Ronald Morgenweck, and Fred Wahlquist of the National Aviation Facilities Experimental Center antenna range.

iii l

INTRODUCTION

Purpose Background

DISCUSSION

General Test Environment Antenna Measurements

TABLE OF CONTENTS

Installation and Environmental Considerations Test Results

CONCLUSIONS

RECOMMENDATIONS

APPENDICES

A - CA-1594/A VHF Narrowband Coaxial Dipole Antenna B - FA-7957A VHF Broadband Coaxial Dipole Antenna C - FA-5675 VHF Elliptically Polarized (Swastika) Antenna D - FA-5668 UHF Discone Antenna E - Antenna Products DPV-22 UHF Gain Antenna F - Collins 437B-7 UHF Gain Antenna G - DP Products DB-224 VHF Folded Dipole Gain Antenna H - DB Products DB-230 VHF Directional YAGI Antenna I - DB Products DB-286 VHF Directional YAGI Array J - KRECO SC-155BN Multiple-Skirt Coaxial Dipole Antenna K - KRECO VB-155BN VHF Directional YAGI Antenna L - KRECO C0-156A VHF Grounded Dipole Antenna M - KRECO CP-156A VHF Grounded Dipole Antenna with Ground Plane N - Phelps Dodge VHF Gain Antenna 0 - Radionics 5731 VHF Dipole Antenna P - Radionics 5831 UHF Dipole Antenna Q - TACO D-2216 VHF Dipole Antenna R - TACO D-2217 UHF Dipole Antenna S - TACO D-2213 (V-U) Twin Dipole Collinear Array T - TACO D-2212 (V-V) Twin Dipole Collinear Array U - TACO D-2260 (V-V-V) Triple Dipole Collinear Array V - TACO Y-102-B-130 VHF Directional YAGI Antenna W TACO Y-41-129 VHF Directional Screen YAGI Antenna X - TACO D-2261 VHF Gain Antenna Y - TACO D-2262 UHF Gain Antenna v

Page

INTRODUCTION

PURPOSE.

The purpose of this project was to test, evaluate, and analyze a select group of very high frequency (VHF) and ultrahigh frequency (UHF) air/ground (A/G) communications antennas, and to obtain antenna reference data for use in the design, development and specification of an improved radiating system for

,_,.,. enroute, terminal, and flight service station A/G conttnunication,s.

BACKGROUND.

The continuing growth in air traffic has brought about· a corresponding increase in the number of A/G channels required for enrqute, terminal and flight service station communications. To provide additional A/G communica tions channels, the Federal Aviation Administration (FAA) Administrator issued a notice of policy decision in May 1973, to reduce the spacing between exist ing A/G channels from 50 kilohertz (kHz) to 25kHz. To reduce radiofrequency interference (RFI) caused by collocated FAA transmitters, F~Order 6610.3, dated April 17, 1975, authorized communications transmitter output power to be reduced from 50 to 10 watts. The combination of additional A/G communica tions channel assignments with narrow bandwidth requirements for 25 kHz channel spacing, and the 7 decibel (dB) reduction in transmitter power output has increased the problem of providing adequate A/G communications coverage.

Along with the modernization and replacement of obsolescent equipment, the present A/G communications system requires many other improvements to reflect changes in technology. This project was established to test, evaluate and analyze a select group of off-the-shelf, state-of-the-art, VHF and UHF A/G communications antennas and compare their operating characteristics with current in-use FAA specified antennas. Many different type antennas were tested at the National Aviation Facilities Experimental Center (NAFEC) antenna range. Some of the test measurements are included in the appendices to this report to serve as antenna reference data. The use of a specific manufacturers' antenna was considered to be a representative type antenna only and not an endorsement of their product •

DISCUSSION

~=- GENERAL.

Most FAA A/G communications sites presently use the elliptically polarized (swastika) antenna for transmitting service, and the vertically polarized coaxial dipole for receiving service in the VHF A/G communications frequency band of 118 to 136 megahertz (MHz). Also, a vertically polarized discone antenna is used for communications with military aircraft in the 225 to 400 MHz frequency band . Other type FAA specified antennas can Be found at some A/G communications facilities; however, they constitute a small percentage of the total antenna complement and are not covered in this report.

Commercially available antennas have been installed at A/G communication facil ities with coverage problems. A representative sample of these nonstandard antennas was tested at NAFEC and compared with FAA specified antennas. The results of this test effort are included in this report to provide reference data for use in the design and specification of an improved A/G communications radiating system.

TEST ENVIRONMENT.

The test measurements included in this report were made at the NAFEC antenna range shown in figure 1. This range consists of a transmitter site and receiver site located approximately 1,000 feet apart on opposite sides of the Atlantic City reservoir.

A

The transmitter site has a Rohde and Schwarz signal .source type SLSV·BN410Q2 that· was adj~sted to provide a radiofrequency (RF) . continuous wave (CW) signal of 5 volts into a 50 ohm source antenna at test frequencies of 118, 127, 136, 225, 300, and 400 MHz. The source antenna, a Scientific-Atlanta Series 26 log-periodic dipole array, was mounted on an adjustable positioning mechanism to permit the changing of antenna alignment and polarization • .

The receiver site contained the test antenna positioning and control system, receiving system, and pattern recorder. The antenna positioner consisted of an Ant Lab azimuth-6ver-elevation pedestal moubted on top of a 30-foot tower and connected to pos1tion indicators, remote direction controls, and variable speed controls located inside the trailer at the base of the tower. A rotary joint in the antenna pedestal permits the antenna under test to rotate freely without disconnecting the feed c;:able.

The receiving system, a Scientific-Atlanta Seyies 1640 precision ~mplitude receiver, has a 40 dB dynamic range with a bolometer output for operating the Scientific-Atlanta Series . l530A polar recorder.

FIGURE 1. NAFEC ANTENNA RANGE

ANTENNA MEASUREMENTS.

An antenna is one of the principle components in the A/G radiating system and serves as the connecting link between free space and the transmitter or receiver by transforming the electromagnetic energy contained in the trans mission line to that of free-space propagation or vice versa. The parameters most often used to describe antenna properties are polarization, input imped ance, radiation pattern, gain, and bandwidth. A description of the antenna measurements and measurement techniques are included in this section of the report while the measurement data for each antenna are included in the appendix for that specific antenna.

POLARIZATION. The polarization of an antenna is defined by the orientation of the electric vector of the wave radiated by the antenna. Thus, a vertical dipole antenna above ground will radiate vertical polarization and have a cir cular pattern in the horizontal (H) plane and a figure-eight (cosine) pattern in the vertical (E) plane. Vertical polarization offers the advantage that interference phenomena which may occur between the direct ray and the reflected ray are for the most part eliminated.

The design polarization of emissions for VHF A/G communications in the International Aeronautical Mobile Service is vertical. Many FAA facilities use the swastika antenna which has elliptical polarization (both horizontal and vertically polarized components); however, it is planned to replace them with vertically polarized antennas in the near future.

INPUT IMPEDANC~. Antenna input impedance is the parameter which relates the antenna to the transmission line and is used to measure the efficiency of energy transfer into or from the antenna. All FAA specified antennas were designed to operate with a 50 ohm impedance and have an initial voltage standing wave ratio (VSWR) tolerance/limit of 2.0:1 or less.

Antenna input impedance was determined with VSWR measurements using the Alford Model 1026C-6 slotted line, a Hewlett-Packard Model 415-E standing wave ratio meter, and a Smith Chart. All VSWR measurements were made with each antenna mounted 30 feet above ground on a crank-up tower and connected to the slotted line with a 50 foot length of RG-214/U coaxial cable. To obtain a true antenna VSWR (at the antenna terminals) a 2.0:1 mismatch was installed on the end of the 50-foot cable and this VSWR value was used to calibrate the standing wave ratio meter readings for cable attenuation at the test frequencies.

RADIATION PATTERNS. The radiation pattern of an antenna is a graphical representation of the magnitude of the relative electric field strength radiated from an antenna in a given plane, plotted against the direction from a given reference. A free-space radiation pattern is required as a basis for determining the antenna performance even though in an operating environment reflections from the antenna supporting structure, other antennas, and extraneous objects cause considerable pattern distortion.

Both H-plane and E-plane radiation patterns were made for eac,h antenna at __ the low, center, and high end . of its designed frequency range. The center bequency radiation patterns for each anten~a .ire included in the report appendices, while all other _ patterns are available at NAFEC in the project file.

GAIN. The power gain of an antenna is defined as the ratio of the radi~tien intensity of the antenna in a given direction (usually on the horizon) to the maximum radiation intensity of a lossless reference antenna (usually a half-wave dipole) with the same input power. Antenna gain is usually expressed 1!} in dB over the gain of a lossless half-wave dipole (dBd), or · in dB over the gain o-f · an isotropic radiator (dBi). The isotropic radiator is a hypothetical antenna which radiates uniformly in all. directiOJ1S .and has 2.15 dB less gain -~ than a lossless half-wave dipole antenna. ~

Gain measurements were made at the NAFEC antenna range by comparing .the test antennas to the Scientific-Atlanta Series 15 adjustable standard gain dipole antennas. .The Series 15 standard gain antennas. have moveable_ elements which permit their length to be adjusted to a half-wavelength at the test frequency.

An adjustable coaxial balun-impedance transformer within the antenna support mast is used to match the adjustable antenna elements to the 50 ohm transmis sion line. When the dipole elements and balun-impedance transformer are set to the etched test frequency calibration marks, these Series 15 antennas have gains of a half-wavelength dipole :(0 dBd or +2.15dBi).

BANDWIDTH. The bandwidth of an antenna is the frequency range over which the~ antenna performs within all the electrical perforinance specifications. Many factors, such as the deterioration of impedance characteristic, change in pattern shape, and loss of· gain are used to determine antenna bandwidth.

ISOLATION. Isolation in a multiantenna environment _is obtained by either physically or electrically separating the radiated waves that are interacting with each other. Isolation from the antenna supporting structure is also an important consideration.

Vertical stacking of antennas is one method of achieving isolation in a limited space. The multiple dipole collinear array concept, used by the Technical Appliance Corporation (TACO), employs vertical stacking with a method of shield ing the feed cables to improve radiation pattern characteristics and also achieve a high degree of isolation between antennas -in a closely spaced array.

The TACO collinear array antennas tested at NAFEC consisted of the D-2212 (VHF-VHF), D-2213 (UHF-VHF), D-2260 (VHF-VHF-VHF) D-2118 (UHF-VHF-UHF) and the D-2218 (VHF-UHF-VHF) antennas . :<:

INSTALLATION AND ENVIRONMENTAL CONSIDERATIONS.

A realistic approach in improving the FAA A/G radiating more than just using efficient and effective antennas.

antenna would be best for a specific application, many size, .weight, installation requir~ments, environmental and expected life cycle become very important.

sys-tem must involve When deciding which factors such as cost, problems, reliability, The FAA uses approximately 25,000 A/G communications antennas in the National Airspace System. Therefore, any small increase in cost becomes very signifi cant when multiplied by the number of antennas required.

Antenna size and weight are important factors when considering shipping, stor age, handling~ and installation requirements. The ability of one man, working alone, in adverse weather conditions, to repair or replace a .defective antenna is a most important installation consideration. Most FAA antennas are presently installed on standard mounting brackets, therefore, the mounting requirements for any new type antenna should be compatible with these brackets if at all possible.

The antenna is a passive device with no moving··~ parts to 'wear ·out, therefore, it is reasonable to expect that a new type antenna using state-of-the-art techniques to overcome environmental problems should provide at least 20 years of trouble free service. Environmental problems such as wind loading, weather fatigue, ice conditions, chemical decomposition, and galvanic corrosion due to the action of dissimilar metals in a salt air environment are important factors which relate to the reliability and the expected life cycle of an antenna and must be considered.

TEST RESULTS.

The antenna range measurement data in the appendices of this report show that an improvement in A/G conununications coverage could be obtained by replacing the FAA specified VHF broadband coaxial dipole and elliptically polarized (swastika) antennas with commercially available antennas. Communications coverage flight test measurements at NAFEC and at various field facilities have shown that a significant improvement occurred when some of these non standard antennas were used to replace the FAA specified antennas. These flight test data can be found in the Advanced Communications Systems Support Project report, prepared by the Verve Research Corporation under Contract DOT-FA75WA1-570, in the NAFEC Technical Letter Report NA-77-60-LR, and in the project file.

INPUT IMPEDANCE. Antenna input impedance in the 118 to 400 MHz frequency band is measured by determining the type of mismatch the antenna produces when it is connected to a transmission line. The measurement of transmission line VSWR permits the determination of antenna input impedance by means of a Smith chart.

The VSWR measurements in the appendices of this report were made with the antenna under test, mounted on a crank-up tower 30 feet above ground, and clear of reflecting objects. VSWR is not constant along a transmission line;

therefore, the VSWR measurement should be made at the antenna terminal.

However, at many installations, making a VSWR measurement at the antenna term inal is impractical. When the VSWR measurement is not made at the antenna terminal, the change in SWR, due to cable attenuation, should be considered.

The HP-415E SWR meter was calibrated for change due to cable loss by instal ling a 2.0:1 mismatch element on the 50-foot length of cable used to connect the antenna under test to the slotted line. The dotted line in figure A-2

>Of appendix A illustrates that the 2. 0:1 mismatch through the 50-foot length of RG-214 coaxial cable ha~ · a VSWR meter value of 1.67:1 at 118 MHz, and 1.65:1 at 136 MHz, due to cable attenuation. The dotted line in figure D-2 of appendix D shows the 2.0:1 mismatch has a VSWR meter value of 1.58:1 at 225 MHz, and 1.44:1 at 400 MHZ, due to cable attenuation.

When cable attenuation ·.is taken into consideration, the following antenna VSWR values are obtained. The FA-5675 antenna in appendix C has a VSWR value of less than 2.0;1 at the antenna terminal between 119 MHz and 133 MHz. The ~~ Radionics antenna in appendix 0 has a VSWR value at the antenna of less than 2.0:1 across the 118 to 136 MHz frequency. band.

~ . j

RADIATION PATTERNS. Both th:e H-:plane and · the E-plane radiation patterns in the appendices of this report were made with the antennas mounted on a wooden support at least 5 feet above the antenna pedestal (12 feet above the tower platform). All patterns were made with the ant~nna under test operating in the receive mode. However, due to the principle of reciprocity, the results would be the same if the antennas under test were operating in the t~ansmit mode.

An omnidirectional antenna is an antenna having an essentially nondirective patt.etn in azimuth and a directive pattern in elevation (ASA standard). The relative gain of an omnidirectional antenna in any azimuth direction should not vary from the mean value by more than +1.5 dB for 360° of rotation (EIA standard). Figures A-3 and A-4 in appendix A show the vertical and horizontal radiation pattern for a typical omnidirectional, vertically-polarized, half wave dipole antenna. Figure B-3 and figure U-9 show distorted vertical radia tion patterns caused by antenna currents flowing in the shield of the coaxial feed cable.

Figures A-5, B-5, and Q-4, were included in the appendices of this report to show the vertical pattern distortion that occurs when a 5-f oot length of 1-1/4 inch aluminum mounting pipe was attached to the base of the antennas. The 25 dB loss of signal on the horizon shown in figure B-5 was caused by antenna cur rent being coupled into the 5-foot mounting pipe dir~ctly beneath the antenna.

This is a principle reason for ,coverage problems when this type antenna is used for A/G communications. The TACO D-2216 antenna (appendix Q) had the least amount of pattern distortion of all the broadband omnidirectional antennas tested at NAFEC.

Directional antennas can be used to improve coverage and reduce interference when the antenna site is not located in the center of the coverage area.

Radiation patterns for directional antennas can be found in appendices H, I, K, V, and w. Appendix V also contains patterns of directional antennas when they are both stacked and skewed.

A directional antenna has one or more major lobes in the horizontal pattern whose maximum relative gain exceeds the minimum relative gain by more than 3 dB.

The horizontal beamwidth of a directional antenna is the angular width, including maximum radiation; measured between two points on the major lobe· of the hori zontal pattern 3 dB 'below the maximum. For example, the horizontal beamwidth of the DB-224E antenna shown in figure G-4 is 160°.

The vertical beamwidth of an antenna is defined as the angular width, including maximum radiation, measured between the two points on the major lobe of the vertical pattern 3 dB below the maximum. The vertical beamwidth of the DPV-22 antenna shown in figure E-3 is 14°.

The elevation beam tilt of an antenna is defined as the angle between the direction of maximum radiation and the horizontal plane. The beam tilt of the DPV-22 antenna shown in figure E-3 is 8° above the horizon.

The elevation beam tilt loss of an antenna is the difference between .the maximum radiation and the radiation in the horizontal plane expressed in dB. The beam tilt loss of the DPV-22 antenna shown in figure E-3 is 4 dB.

GAIN. Antenna gain measurements included in this report were made by comparing the antenna under test to a standard gain dipole antenna. After each horizontal radiation pattern was made, the antenna under test was replaced :by the standard gain antenna and a dot representing the standard gain antenna receive level was placed on the 0 or 90° rad'ial. The gain of each antenna in dBd can be found by comparing the dB difference between the gain dot and the antenna .under test radiation pattern ievel. The antenna gain in dBi can be found by adding 2.15 dB to the dBd measurement, however, in practice only integral dB values are used and the .15 dB value is dropped.

The pri1,1ciples of antenna design and how to direct or shape the radiation pattern to obtain effective radiated power gain are well established. Gain in an omni directional antenna is obtained by compressing the vertical radiation pattern closer to the horizon as shown in figures E-3, F-3, G-3, X-3, and Y-3. Gain in a unidirectional or bidirectional antenna is obtained by compressing the hor izontal radiation pattern as shown in figures G-4, H-4, I-4, K-4, V-4, and W-4.

The unidirectional yagi antenna array in appendix I can be made bidirectional by reversing the direction of one of the three element yagi sections.

To assist in making the gain measurements, a standard gain antenna reference level dot was also placed on some of the vertical radiation· patterns. For example, the standard gain antenna reference level dot on the horizontal radia tion pattern (figure E-4 of appendix E) for the DPV-22 antenna shows that this antenna has less than dipole gain. However, the standard gain antenna reference level dot on the vertical radiation pattern (figure E-3 of appendix E) shows the DPV-22 antenna has 4 dB of gain more than a dipole 8° above the horizon.

BANDWIDTH. An antenna that was designed to cover a broadband of frequencies will usually not have as low a VSWR or as much gain as an antenna designed for a nar rowband of frequencies. Many of the broadband antennas tested at NAFEC with a VSWR of 2.0:1 or less across the 118 to 136 MHz frequency band had pattern distortion and loss of gain within the band. This condition was not found in the narrowband antennas.

ISOLATION. Isolation measurements between dipole elements in the TACO collinear array antennas were made with the antennas under test installed on a crank-up tower 30 feet above ground and clear of reflecting objects. The isolation between antenna elements measured greater than 30 dB in all cases.

Isolation between the antennas and a metalic supporting structure was investi gated with radiation pattern measurements. Lack of isolation between the antennas and the supporting structure caused pattern distortion as shown in figures A-5, B-5, and Q-4.

CONCLUSIONS

Based on the data collected, evaluated, and presented in this report, it is concluded that:

1. FAA A/G communications antenna specifications do not include sufficient radiation pattern requirements and thereby have permitted the use of antennas with marginal radiation characteristics.

2. The FAA specified broadband VHF dipole and elliptically polarized (_swastika) antennas are inefficient and could cause A/G cptmimnications coverage problems.

t._· ·-. i •

3. The broadband UHF discone and dipole antennas have similar operating characteristics. However, a VHF dipole antenna sealed inside a fiberglass enclosure should provide more reliable communications in adverse weather conditions.

4. The omnidirectional gain antennas tested at NAFEC that had a gain of more than +2 dBd become excessive in length and lost overhead coverage.

5. Directional antennas can be used to provide an effective radiated power (ERP) gain at FAA communications facilities where omnidirectional coverage is not required.

6. Isolation between antennas in a limited space can be increased by using an antenna with a low profile design and by stacking the antennas in a collinear manner.

7. Some VHF antennas with less than 18 MHz bandwidth had more suitable operating characteristics than the broadband antennas.

8. Additional test, evaluation, and analysis is required to define an optimum FAA Air/Ground Communications Radiating System.

RECOMMENDATIONS

Based on the test results obtained during this test and evaluation effort, it is recommended that:

1. In addition to polarization, input impedance, gain, and bandwidth, future FAA A/G communications antenna specifications should also include definitive radiation pattern and isolation requirements.

2. Broadband VHF antennas with performance characteristics equal to or better than the TACO D-2216 VHF dipole antenn~ be install.ed at A/G communications facilities with coverage problems. · '

3. Broadband UHF dipole antennas that are sealed inside a fiberglass enclosure and have performance characteristics equal to or better than the TACO D-2217 UHF dipole antenna be installed at field facilities with environmental problems.

4. The use of omnidirectional gain antennas should be restricted to those facilities where the cost and coverage requirements can be justified.

5. Directional A/G communications antennas be installed at FAA field facil ities with coverage problems that could be corrected with the use of direc tional antennas.

6. A limited number of collinear array antennas with operating characteristics equal to or better than the TACO D-2212 (VHF-VHF) antenna, and the TACO D-2213 (UHF-VHF) antenna, be obtained and installed with additional on-site test and evaluation.

7. The usefulness of narrow band antennas be investigated for possible communications coverage improvements.

8. A long term test and evaluation project be established at NAFEC to define an optimum air/ground communications radiating system based on antenna range measurements and verified with flight test measurements.

··· APPENDIX A

CA-1594/A VHF NARROWBAND COAXIAL DIPOLE ANTENNA

The CA-1594/A antenna shown in figure A-1 is a vertically polarized, omni- · directional, narrowband coaxial .dipole that was designed to operate in the vHF frequency band of 117 to ·.123 MHz. This antenna was manufactured for the Civil Aeronautics Administration by the Granite State Machine Company, Manchester, New Hampshire und~r contract CCA-32100. The CA-1594/A antenna weighs approximately 6 3/4 pounds and consists of a 22-inch long by l-inch diqmeter radiating element and a 24 1/8-inch long by 2 1/2-inch diameter lower element skirt separated by a 2-inch porcelain insulator. A mounting pipe extends 12 inches below the skirt and has standard 1 1/4 inch pipe thread for attaching the antenna assembly to its mounting bracket.

FIGURE A-1. CA-1594/A COAXIAL DIPOLE ANTENNA

A-1 a::

(I)

> 2.0:1 c r--z z

LLI

1-z c

1.0:1

It- - - f- \ J., ,"" I

FIGURE A-2.

1/

FREQUENCY MHz

77-39-A-2

CA1594/A COAXIAL DIPOLE ANTENNA

2.0: I

1.011

LLI _,

CD

c

:::1:

1-

0::

(I)

VSWR measurements for the CA-1594/A antenna are shown in figure A-2. The numbers on the left side of the graph represent the VSWR values at the antenna terminal. The numbers on the right side of the graph represent the VSWR values with a 50 foot length of RG-214 coaxial cable between the antenna and the slotted line.

The CA-1594/A antenna free space vertical radiation pattern shown in figure A-3 is a typical dipole pattern. Figure A-4 is the horizontal radiation pattern and figure A-5 shows a distorted vertical radiation pattern caused by a 5 foot length of mounting pipe being attached to the base of the antenna.

These radiation patterns were made with the antenna installed 5 feet above the pedestal on a wooden 4-inch by 4-inch support.

The CA-1594/A antenna had dipole gain (0 dBd or +2 dBi) at 120 MHz as shown by the standard gain antenna reference dot on figure A-4.

A-2

SCI ~ i'IIIF IC 1\Tli\Nlllo,INC.

FIGURE A-3. CA-1594/A VERTICAL RADIATION PATTERN

A-3

FIGURE A-4. CA-1594/A HORIZONTAL RADIATION PATTERN

A-4

FIGURE A-5. CA-1594/A DISTORTED VERTICAL RADIATION PATTERN

A-5

APPENDIX B

FA-7957A VHF BROADBAND COAXIAL DIPOLE ANTENNA

The FA-7957/A antenna, shown in figure B-1, is a vertically polarized, omni directional, broadband coaxial dipole that was designed to operate·in the extended VHF air/ground frequency band of 118 to 144 MHz. This antenna was manufactured for the FAA by R. A. Miller Industries Inc., Grand Haven, Michigan, under contract DOT-FA70WA-2366. The FA-7957/A antenna weighs 4 1/2 pounds, is 39 inches long, and consists of a 15 1/4-inch radiating element and a 15-inch skirt separated by a 2-inch ceramic insulator. A mounting pipe extends 6 inches below the skirt and has standard 1 1/4 inch pipe thread for attaching the antenna assembly to a mounting bracket •

FIGURE B-1. FA-7957/A COAXIAL DIPOLE ANTENNA

B-1

0:::

3:

en > 2.0:1 c z z

LLI

1-z c r-

/ 2.0:1

J

LLI

.J

CD

- - - -; - c - - - 0

L

1-

0:::

3:

en

1.0:1 118 127

FREQUENCY MHz

1.0 II

77-39-B-2

FIGURE B-2. FA-7957/A COAXIAL DIPOLE ANTENNA

VSWR measurements for the FA-7957/A antenna are shown in Figure B-2. The numbers on the left side of the graph represent the VSWR values at the antenna terminals and the numbers on the right side of the graph represent the VSWR values with a 50 foot length of RG-214 coaxial cable between the antenna and the slotted line.

The free-space vertical radiation pattern for the FA-7957/A antenna is shown in figure B-3. The horizontal radiation pattern is shown in figure B-4, and a distorted vertical radiation pattern is shown in figure B-5. The distorted vertical radiation pattern was caused by antenna currents being coupled into the 5-foot length of 1 1/4-inch mounting pipe attached to the base of the antenna. This 25 dB loss of signal on the horizon that was caused by attach ing the antenna to a 5-foot length of mounting pipe will vary depending upon the frequency used and the size and composition of the mounting pipe or structure.

The gain of gain dipole on a 4-inch the FA-7957/A antenna at 127 MHz measured 8 dB below the standard (-8 dBd or -6 dBi) when mounted 5 feet above the antenna pedestal by 4-inch wooden support.

B-2

FIGURE B-3. FA- 7957 /A VERTICAL RADIATION PATTERN

B-3

FIGURE B-4. FA-7957/A HORIZONTAL RADIATION PATTERN

B-4

FIGURE B-5.

FA-7957/A DISTORTED VERTICAL RADIATION PATTERN

B-5

APPENDIX C

FA-5675 VHF ELLIPTICALLY POLARIZED (SWASTIKA)ANTENNA

The FA-5675 antenna shown in figure C...,;l is an elliptically polarized, omni directional, broadband antenna that was designed to operate in the VHF air/ ground frequency band of 118 to 136 MHz. This antenna vas manufactured for the FAA by the Antenna Products Company, Mineral Wells, Texas under contract FA65WA-1341. The FA-5675 antenna weighs 18 pounds, is 21 inches high, 36-i~hes square, and consists of an upper and lower hub, each having four dipole elements spaced approximately 1/3 wavelength ~part at the midband frequency and inclined 30° with respect to the horizon. ·Tpe upper and lower hubs are separated by a fiberglass reinforced plastic in~ulator. This antenna was designed to mount on a standard 2 1/2-inch g~lv~nized iron pipe.

"77-39-c-1

FIGURE C-1. FA-5675 ELLIPTICALLY POLARIZED ANTENNA

C-1

(I)

> 2.0:1 -c z z 1&.1 z -c

1.0:1

FIGURE C-2.

FREQUENCY MHz

77-39-C-2

2.0: I

1.011

FA-5675 ELLIPTICALLY POLARIZED (SWASTIKA) ANTENNA

1&.1 _, al -c u X .... -• 0:::

3t (I)

VSWR measurements for the FA-5675 antenna are shown in figure C-2. The numbers on the left side of the graph represent the VSWR values at the antenna terminal and the numbers on the right side of the graph represent the antenna VSWR values with a 50 foot length of RG-214 coaxial cable between the antenna and the slotted line.

The free-space vertical radiation pattern for the FA-5675 antenna is shown in figure C-3 and the horizontal radiation pattern is shown in figure C-4. These patterns were made at the midband frequency of 127 MHz. Some vertical pattern distortion was found on the high and low ends of the band both with and with out a 5-foot length of mounting pipe.

The gain of the FA-5675 antenna measured 3 dB less than the standard gain dipole (-3 dBd or -1 dBi) at 127 MHz as shown in figure C-4. Antenna gain measurements also showed a decrease at the high and low ends of the band.

C-2

FIGURE C-3. FA-5675 VERTICAL RADIATION PATTERN

C- 3 tf

SCI<;;/11 1..: /1fLA~HA. INC.

FIGURE C-4. FA-5675 HORIZONTAL RADIATION PATTERN

C-4

APPENDIX D

FA-5668 UHF DISCONE ANTENNA

The FA-5668 antenna shown in figure D-1 is a vertically polarized _omnidirec tional, broadband discone antenna that was designed to operate in the military air/ground communications frequency band of 225 to 400 MHz. This antenna was manufactured for the FAA by the Antenna Products Company, Mineral Wells, Texas, under contract FA65WA-1203. The FA-5668 antenna weighs 4 1/2 pounds, has overall dime~sions of 15 3/8-inches high by 18 1/2-inches wide, and consists of a 12 5/8 inch diameter radiating disc and a lower hub assembly with six threaded element rods that are each 15 inches long. · A glass reinforced plastic insulator separates the radiating disc from the cone section. This antenna is designed to mount on top of a mast having a maximum diameter of 1 3/4 inches.

FIGURE D-1. FA-5668 UHF DISCONE ANTENNA

D-1 l:r 311:

(I)

C2.0:1 z z

LIJ

z c

2.0=1

I . 0 : I !-A..L___.!.,____J..____Ji.,.__-'----'-----L----lL--;;;~__.l.__--'--L-....1_-L--'--L-....L....::-:::! 1.0 : 1 220 310 400

FREQUENCY MHz 77-39-D-2

FIGURE D-2. FA-5668 DISCONE ANTENNA

1&1 ...1

CD

c u :z: .... -311:

l:r 311:

(I)

VSWR measurements for the FA-5668 antenna are shown in figure D-2. The numbers on the left side of the graph represent VSWR values at the antenna terminals.

The numbers on the right side represent VSWR values with a 50 foot length of RG-214 coaxial cable between the antenna and the slotted line.

The free-space vertical radiation pattern for the FA-5668 antenna is shown in figure D-3 and the horizontal radiation pattern is shown in figure D-4. Some pattern distortion was found at both 225 and 400 MHz.

The gain of the FA-5668 antenna measured 1 dB below the standard gain dipole (-1 dBd or +1 dBi) at 300 MHz as shown in figure D-4. The antenna gain at 400 MHz measured 4 dB below the standard gain dipole.

D-2

FIGURE D-3. FA-5668 VERTICAL RADIATION PATTERN

D-3

' i.

FIGURE D-4. FA-5668 HORIZONTAL RADIATION PATTERN

D- 4

- i

APPENDIX E

ANTENNA PRODUCTS DPV-22 UHF GAIN ANTENNA

The DPV-22 antenna shown in figure E-1 is a vertically polarized, omnidirec tional broadband gain antenna that was designed to operate in the military A/G communications frequency band of 225 to 400 MHz. This antenna is the same as FAA types FA-7881A and FA-7881B per specification FAA-E-2277a that were . manufactured under contracts DOT-FA72WA-3084 and DOT-FA76WA-3763. The DPV-22 antenna was manufactured by the Antenna Products Company, Mlneral Wells, Texas, weighs 35 pounds, is 13 feet long by 4 1/2-inches in diameter, and cost $1,500.00.

The DPV-22 antenna consists of five stacked dipoles connected by a phasing harness which tilts the. beam upwards. The antenna assembly is enclosed in a fiberglass housing which has permanently embedded deicing wires. The mounting bracket at the base of the antenna has two holes, 20 inches center to . center to permit mounting with the use of 1/2 inch through bolts or lag screws.

FIGURE E-1.

E-1

0::

3J en cr2.0=1 z

1--z 1&.1 1-z c( r\.

1.0:1

I "' I

1/

- - - - - - 1- - - - 1/

1\. ~I'\ ,..;~r-,: ~ ~

" v ' )~ \ v 'V \ v

FREQUENCY MHz 77-39-E-2

FIGURE E-2. DPV-22 GAIN ANTENNA

lJ"'

2.0:1

"""''ii:

1.0: I

1&.1 ..J m c( u 1-

3J 0::

3J en

VSWR measurements for the DPV-22 antenna are shown in figure E-2. The numbers on the left side of the graph represent the VSWR values at the antenna ter minal and the numbers at the right side of the graph represent the VSWR values with a 50 foot length of RG-214 coaxial cable between the antenna and the slotted line.

Figure E-3 is the free-space vertical radiation pattern for the DPV-22 antenna at 300 MHz which shows the peak of the main beam to have a 8° upward tilt and a beamwidth of 14°. The horizontal radiation pattern in figure E-4 shows a 2 dB variation in the omnidirectional pattern strength measured on the horizon below the main beam.

The gain of the DPV-22 antenna measured 1 dB below the standard gain dipole at 300 MHz on the horizon and 4 dB above the standard gain dipole at the peak of the main beam, as shown by the standard gain antenna dots on the radiation patterns.

E-2

FIGURE E-3. DPV-22 VERTICAL RADIATION PATTERN

E-3

FIGURE E-4. DPV-22 HORIZONTAL RADIATION PATTERN

E-4

APPENDIX F

COLLINS 437B-7 UHF GAIN ANTENNA

The 437B-7 UHF antenna shown in figure F-1 is a vertically polarized omni directional broadband gain antenna that was designed to operate in the military A/G communications frequency band of 225 to 400 MHz. This antenna was manu factured by the Collins Radio Group of Rockwell International, Dallas, Texas, and weighs 50 pounds, is 5 feet, 9 inches long by 8 inches in diameter, and cost $1.970.00.

This antenna is designed to be vertically stacked, up to four units high, supported only by the lower base flange, and be able to withstand 100 mile per hour winds with 1 inch of radial ice. The antenna consists of two collinearly arrayed radiating elements mounted concentrically around a common central aluminum tube, and foamed in place inside a fiberglass housing. An infinite bandwidth balun is used to provide equal power and equal phase to both dipoles across the band. A 1 1/2-inch diameter tube through the center of the antenna permits cables from other antennas to be brought through the center. The 11 1/2 inch diameter base flange is designed to mount to a support bracket with six 1/2-inch bolts •

FIGURE F-1. 437B-7 UHF GAIN ANTENNA

F-1

0: • en C2.0:1 z -z Ill z c

1.0=1

I l/

'v

FIGURE F-2.

I

- EE I- -

~ v ' -

.... II"""'"

FREQUENCY MHz 77-39-E-2

COLLINS 437B-7 ANTENNA

2.0:1

1.0: I

Ill ..J m c u :r::

0:

• en

VSWR measurements for the 437B-7 antenna are shown in figure F-2. The numbers on the left side of the graph represent the VSWR values at the antenna ter minal and the numbers on the right side of the graph represent the VSWR values with a 50 foot length of RG-214 coaxial cable between the antenna and the slotted line.

Figure F-3 is the free-space verical radiation pattern at 300 MHz which shows an upward tilt with an 82° beamwidth. The horizontal radiation pattern in figure F-4 shows a 1 1/2 dB variation in the omnidirectional pattern strength.

The gain of the 437B-7 antenna measured 2 dB above the standard gain dipole (+2 dBd or +4 dBi) as shown by the standard gain antenna dots on the radiation patterns.

F-2 il ..

FIGURE F-3. 437B-7 VERTICAL RADIATION PATTERN

F-3

:i:

FIGURE F-4. 43 7B-7 HORIZONTAL RADIATION PATTERN

F-4

I

APPENDIX G

DECIBEL PRODUCTS DB-224 VHF GAIN ANTENNA

. The DB_:224 antenna shown in figure G-1 is a vertically .polarized omnidirectional or directional gain antenna that was designed to operate with a center frequency of 127 MHz. This antenna was manufactured by Decibel Products, Inc., Dallas, Texas, weighs 35 pounds; is . .23 · fee·t 9 inches long, and cost $230.00. Due to its size, the DB...;224 antenna was shipped to NAFEC in two 12-foot sections for ease of handling with each section consisting of two folded dipole elements and a cable harness • . An omnidirectional radiation .pattern is obtained with this antenna when all four dipole elements are evenly spaced every 90° around the mast. When all four dipoles are aligned on one side of ·the mast this antenna has directional characteristics and is designated as a DB-224E antenna.

FIGURE G-1. DB-224 VHF GAIN ANTENNA

G-1 a:

>2.0:1 c

1-z z

LLI

z c

1.0:1

FREQUENCY MHz

I

I

- -r - -

'I'

77-39-G-2

FIGURE G-2. DB-224 GAIN ANTENNA

2.0:1

1.0•1

LLI

..J

CD

c u a:

(f)

VSWR measurements for the DB-224 antenna are shown in figure G-2. The numbers on the left side of the graph represent VSWR values at the antenna terminal and the numbers on the right side of the graph represent VSWR values with a 50 foot length of RG-214 coaxial cable between the antenna and the slotted line.

Figure G-3 is the vertical radiation pattern for the DB-224E antenna at 127 MHz. This vertical pattern shows the peak of the main beam to have a slight downward tilt and a 17° beamwidth. Figure G-4 is the horizontal radiation pattern for the DB-224E antenna which shows the offset directional characteristics when the four dipole elements are aligned on one side of the mast.

The gain of the DB-224E antenna measured 6 dB above the standard gain antenna (+6 dBd or +8 dBi) at 127 MHz on the peak of the main beam, as shown.by the standard gain antenna dots on the radiation patterns. In the omnidirectional configuration, the antenna measured 3 dB above the standard gain dipole.

G-2

,ii SCtf.NliFIC ATLi\NT-', iNC·

FIGURE G-3. DB-224E VERTICAL RADIATION PATTERN

G-3

FIGURE G-4. DB-224E HORIZONTAL RADIATION PATTERN

G-4

APPENDIX H

DB PRODUCTS DB-230 VHF DIRECTIONAL YAGI ANTENNA

The DB-230 antenna shown in figure H-1 is a vertically polarized~ directional YAGI antenna that was designed to operate with a center frequency of 127 MHz.

This three-element YAGI antenna was manufactured by Decibel Products, Inc., Dallas, Texas, and weighs 6 1/2 pounds, is 51 inches long, 46 1/2 inches high, costs $128.00, and consists of a 40-inch director, a 43 7/8-inch radiator, and a 46 1/2-inch reflector, spaced 19 3/4 inches apart on a 51-inch support boom.

A 1 3/4-inch aluminum angle welded to the support boom is used to mount this antenna to a support pipe.

FIGURE H-1. DB-230 DIRECTIONAL YAGI ANTENNA

H-1

0:

:r;

en > 2.0:1 c z z LIJ .... z c

1.0:1

FIGURE H-2.

\ I \ I

=1='8- I

-1 - - ~ I ,,.I

FREQUENCY MHz

77-39-H-2

DB-230 DIRECTIONAL YAGI ANTENNA

2.0:1

1-

1.0•1

LIJ

;..J

CD

c c.,)

::z:: .... -31 0:

:c en

VSWR measurements for the DB-230 antenna are shown in figure H-2. The numbers on the left side of the graph represent VSWR values at the antenna terminal and the numbers on the right side of the graph represent VSWR values with a

50. foot length of RG-214 coaxial cable between the antenna and the slotted line.

Figure H-3 is the vertical radiation pattern at 127 MHz. This pattern shows a vertical beamwidth of 60° with a downward tilt. Figure H-4 is the horizontal radiation pattern which shows this antenna has a horizontal beamwidth of 90°.

The gain of the DB-230 antenna measured 6 dB above the standard gain dipole (+6 dBd or +8 dBi) at 127 MHz on the peak of the main beam, as shown by the standard gain antenna dots on the radiation patterns.

H-2

• ii

FIGURE H-3. DB-230 VERTICAL RADIATION PATTERN

H-3

FIGURE H-4. DB-230 HORIZONTAL RADIATION PATTERN

H-4

•_i ...

APPENDIX I

DB PRODUCTS DB-286 VHF DIRECTIONAL YAGI ARRAY

The ~ DB~286 antenna shoWn in figure I-1 is a vertically polarized, directional ·· YAGI array that was designed to operate with a center frequency of 127 MHz.

This antenna array was manufacturbd by Decibel Products, Inc~, Dallas, Texas, and weighs 15 1/4 pounds, is 40..:inches long by 40-incheswide by 46 1/2-inches high, cost $195.00 and consists of two 3-·element yagis spaced 1/2 wavelength apart . that are fed in phase through a quarter wave transformer. Each 3-element YAGI contains a 46 1/2-inch long reflector, a 44-inch radiator, and a 40 1/2-inch director that are spaced 19 inches apart on a 39 1/2-inch support boom. A 1 3/4-inch aluminum angle is welded to the 36-inch crossboom to permit the mou~ting of this antenna array on a support pipe. ·

FIGURE I-1. DB-286 DIRECTIONAL YAGI ARRAY

I -1

(I)

> 2.0:1 c z z z c

1.0 :I

"\ I \ if

\ / - - - - -=T - - - ~ - - - - - - ' l \ l

\!to.. , ' ..

FREQUENCY MHz 77-39-I-2

FIGURE I-2. DB-286 DIRECTIONAL YAGI ARRAY

2.0:1

1.011

..J

CD

c

0:::

(I)

VSWR measurements for the DB-286 antenna are shown in figure I-2. The numbers on the left side of the graph represent VSWR values at the antenna terminal and the numbers on the right side of the graph represent VSWR values with a 50 foot length of RG-214 coaxial cable between the antenna and the slotted line.

Figure I-3 is the vertical radiation pattern at 127 MHz which shows this antenna has a 51° vertical beamwidth with a downward tilt. Figure I-4 is the horizontal radiation pattern which shows a horizontal beamwidth of 57°.

The gain of the DB-286 antenna measured 8 dB above the standard gain dipole (+8 dBd or +10 dBi) at 127 MHz on the peak of the main beam, as shown by the standard gain antenna dots on the radiation patterns.

I-2 t • c

SCIENliFIC ATLANTA, INC•

FIGURE I-3. DB-286 VERTICAL RADIATION PATTERN

I-3

FIGURE I-4. DB-286 HORIZONTAL RADIATION PATTERN

I-4

APPENDIX J

KRECO SC-155BN MULTIPLE-SKIRT COAXIAL DIPOLE ANTENNA

The SC-155BN antenna shown in figure J-1 is a vertically polarized, omnidirec tional, multiple-skirt coaxial dipole that was designed to operate with a center frequency of 127 MHz. This antenna was manufactured by the H. Kreckman Company, Cresco, Pennsylvania and costs $138.00. When the SC-155BN antenna elements were assembled on a government furnished 12-foot long, 1 1/4 inch thick wall aluminum pipe the antenna assembly weighed 27 pounds and·was 14-foot long. The supplied antenna elements consisted of a 20 1/2-inch long radiating el~ment, three 22 3/4-inch skirts, a glass insulator hub assembly and a ground-plane assembly. The glass insulator hub assembly has standard 1 1/4-inch pipe thread for mounting on a support pipe •

FIGURE J-1. SC-155BN MULTIPLE-SKIRT COAXIAL DIPOLE

J-1

3l U) > 2.0:1 -c z z 1.&1 1-z c

1.0:1

FIGURE J-2.

FREQUENCY MHz 77-39-JNZ v

2.0: I , 1.0•1

KRECO SC-155BN MULTIPLE-SKIRT COAXIAL ANTENNA

1.&1

CD

c u 1-a:

3l U)

VSWR measurements for the SC-155BN antenna are shown in figure J-2. The numbers on the left side of the graph represent VSWR values at the antenna terminal and the numbers on the right side of the graph represent VSWR values with a 50 foot length of RG-214 coaxial cable between the antenna and the slotted line.

Figure J-3 is the vertical radiation pattern at 127 MHz which shows a vertical beamwidth of 107° and approximately 4 dB of pattern distortion below the peak of the main beam. Figure J-4 is the horizontal radiation pattern which shows a less than 1/2 dB variation in the omnidirectional pattern.

The gain of the SC-155BN antenna was equal to the standard gain dipole (0 dBd or +2 dBi) at 127 MHz, as shown by the standard gain antenna dots on the radiation patterns.

J-2

FIGURE J-3. SC-155BN VERTICAL RADIATION PATTERN

J-3

FIGURE J-4. SC-lSSBN HORIZONTAL RADIATION PATTERN

J-4

APPENDIX K

KRECO VB~l55BN VHF DIRECTIONAL YAGI ANTENNA

The VB-155BN antenna shown in figure K-1 is a vertically polarized, three element, directional YAGI that was design'ed to operate with a center frequency of 127 MHz. This antenna was manufactured by the H. Kreckman Company, Cresco, Pennsylvania, and cost .$112.00.