A TECHNICAL BRIEFING FOR AMATEUR RADIO OPERATORS ANTENNA

A TECHNICAL BRIEFING FOR AMATEUR RADIO OPERATORS “ANTENNA GAIN: TRUTHS AND MYTHS” PRESENTED TO: ARASWF NAPLES, FL 34119 JANUARY 2016 PRESENTED BY: DR. AL TORRES KP 4 AQI EMAIL: atorres 4850@yahoo. com 1

For Year 2016 • January 2016: “Antenna Gain: Truths and Myths” • February 2016: “Slot Antennas: Wire Reciprocity” • March 2016: “Fractal Antennas and Metamaterial Antennas” 2

PRESENTATION OUTLINE • WHAT IS ANTENNA GAIN • ANTENNA GAIN EXAMPLES • TYPICAL EFFECIENCY VALUES FOR ANTENNAS • ANTENNA GAIN MEASUREMENTS • STANDARD GAIN HORNS (SGH) • COMMERCIAL ANTENNAS AND THEIR STATED GAINS • SUMMARY 3

WHAT IS ANTENNA GAIN • ANTENNA GAIN IS THE PRODUCT OF ANTENNA EFFICIENCY TIMES ANTENNA DIRECTIVITY G= D • IS ANTENNA EFFICIENCY WHICH IS MADE FROM THE SUM OF RADIATION RESISTANCE AND OHMIC RESISTANCE = (Rr + Ro) • • D IS ANTENNA DIRECTIVITY AND IT IS A FUNCTION OF THE TYPE OF ANTENNA DIRECTIVITY FOR AN ANTENNA IS DEFINED AS: D= 4 (Ae/ 2) – is wavelength and Ae is Antenna Effective aperture (size) 4

ANTENNA GAIN EXAMPLES • • RADIATION RESISTANCE SHOULD BE AS HIGH AS POSSIBLE OHMIC RESISTANCE SHOULD BE AS LOW AS POSSIBLE • • TYPICAL RADIATION RESISTANCE FOR A DIPOLE IS 73 OHMS TYPICAL OHMIC RESISTANCE FOR A COPPER DIPOLE IS 6 OHMS EFFICIENCY IS ~ 92% THEORETICAL GAIN FOR A DIPOLE IS 2. 14 d. Bi (100% EFFICIENT) • PRACTICAL GAIN FOR A COPPER DIPOLE IS 1. 98 d. Bi 5

CONDUCTIVITY OF METALS Conductor Conductivity ( m) Carbon (Graphene) 1. 0 x 10 -8 Silver 1. 59 x 10 -8 59% Copper 1. 68 x 10 -8 6% Gold 2. 44 x 10 -8 1. 53 Aluminum 2. 82 x 10 -8 1. 77 Zinc 5. 90 x 10 -8 3. 71 Nickel 6. 99 x 10 -8 4. 40 Iron 1. 00 x 10 -7 6. 29 Stainless Steel 6. 90 x 10 -7 10. 62 Nichrome 1. 10 x 10 -6 63. 0 6

TYPICAL EFFICIENCY VALUES FOR ANTENNAS • • SILVER MONOPOLE: SILVER DIPOLE: COPPER MONOPOLE: COPPER DIPOLE: 95% 94% 93% 92% • ALUMINUM ANTENNAS: – WITHOUT TRAPS: – WITH TRAPS: 50 -60% 55% 40% • • RUBBER DUCK ANTENNAS: DUMMY LOAD: 20% 1% 7

ANTENNA GAIN MEASUREMENTS • THERE ARE TWO BASIC METHODS THAT CAN BE USED TO MEASURE ANTENNA GAIN: ABSOLUTE-GAIN AND GAINTRANSFER (GAIN COMPARISON) MEASUREMENTS • ABSOLUTE-GAIN: THIS METHOD IS USED TO CALIBRATE ANTENNAS THAT CAN THEN BE USED AS STANDARDS FOR GAIN MEASUREMENTS, AND IT REQUIRES NO A PRIORI KNOWLEDGE OF THE GAINS OF THE ANTENNAS • GAIN-TRANSFER: THIS METHOD MUST BE USED IN CONJUNCTION WITH STANDARD GAIN ANTENNAS TO DETERMINE THE ABSOLUTE GAIN OF THE ANTENNA UNDER TEST 8

STANDARD GAIN HORNS (SGH) Model Frequency E-Plane H-Plane Maximum Continuous Power Antenna Factor Gain Typical Field Strength 3160 -01 0. 96 - 1. 46 GHz 26° 27° 550 W 15. 4 d. B (1/m) 16. 5 d. Bi 700 V/m 3160 -02 1. 12 - 1. 70 GHz 26° 550 W 16. 9 d. B (1/m) 16. 3 d. Bi 700 V/m 3160 -03 1. 70 - 2. 60 GHz 27° 550 W 20. 6 d. B (1/m) 16. 3 d. Bi 650 V/m 3160 -04 2. 60 - 3. 95 GHz 26° 27° 250 W 23. 7 d. B (1/m) 16. 7 d. Bi 500 V/m 3160 -05 3. 95 - 5. 85 GHz 26° 27° 250 W 27. 3 d. B (1/m) 16. 7 d. Bi 500 V/m 3160 -06 5. 85 - 8. 20 GHz 24° 250 W 29. 9 d. B (1/m) 17. 1 d. Bi 500 V/m 3160 -07 8. 20 12. 40 GHz 26° 250 W 33. 5 d. B (1/m) 16. 9 d. Bi 500 V/m 3160 -08 12. 40 18. 00 GHz 26° 27° 200 W 37. 1 d. B (1/m) 16. 7 d. Bi 435 V/m 3160 -09 18. 00 26. 50 GHz 27° 50 W 40. 3 d. B (1/m) 16. 8 d. Bi 220 V/m 3160 -10 26. 50 40. 00 GHz 27° 10 W 43. 5 d. B (1/m) 17. 0 d. Bi 100 V/m 9

GAIN MEASUREMENTS • THE LOWEST FREQUENCY FOR SGH IS 300 MHZ; THERE ARE NO STANDARDS BELOW THIS FREQUENCY • ENGINEERS HAVE TRIED TO USE 1/2 DIPOLES AS STANDARDS DOWN TO 100 MHZ. MEASUREMENTS HAVE TOO MUCH VARIABILITY FOR MAKING GAIN-TRANSFER MEASUREMENTS • THE TYPICAL RESONANT 1/2 DIPOLE (WITH A GAIN OF 2. 14 d. Bi), IN FREE SPACE, EXHIBITS A HIGH DEGREE OF POLARIZATION PURITY. HOWEVER BECAUSE OF ITS BROAD PATTERN, ITS POLARIZATION MAY BE SUSPECT IN OTHER THAN REFLECTION-FREE ENVIRONMENTS 10

GAIN MEASUREMENTS • TYPICAL ANECHOIC CHAMBERS GO DOWN TO ~ 200 MHZ • ACCURATE GAIN MEASUREMENTS BELOW 300 MHZ ARE NOT POSSIBLE 11

HF YAGI ANTENNAS AND GAINS 12

THREE ELEMENT YAGI FOR 2 METERS CUSHCRAFT • A 13 B 2 3 Element Wideband Boomer The A 13 B 2 is as versatile as the A 17 B 2 is specialized. A 13 B 2 will be your choice for high performance across the entire 2 meter band. New and experienced hams will enjoy 15. 8 d. Bi gain on FM, packet, CW, or sideband across the 4 MHz operating range. The A 13 B 2 is easily mounted vertically or horizontally for maximum performance on your favorite mode. Its optimum boom length makes it a popular antenna that fits just about anywhere. The new Ultra. Match balanced feed on the A 13 B 2 provides a 50 Ohm match via a standard SO-239 UHF female connector. 13

CUSHCRAFT YAGI ANTENNAS GAIN VALUES HOW WERE THESE MEASUREMENTS DONE? LIERS! 14

MFJ-18522 -METER YAGI, 6 EL. , 144 -148 MHZ, WIDE BAND • Our versatile new six-element MFJ-1852 2 -Meter Band Spanner Yagi delivers 10 -d. Bi gain, 20 -d. B front-to-back ratio, and covers 144 to 148 MHz plus WEFAX and MARS with rock bottom SWR. • HOW WAS THIS MEASUREMENT DONE? WHAT STANDARDS? MUST BE PFM • LIER, LIER! 15

SUMMARY • WE HAVE DEFINED WHAT ANTENNA GAIN IS • ANTENNA GAIN IS MOSTLY DETERMINED BY THE ANTENNA DIRECTIVITY AND ITS EFFICIENCY (MOSTLY OHMIC LOSSES) • WE HAVE ALSO DEFINED DIRECTIVITY WHICH IS PROPORTIONAL TO ANTENNA SIZE AND WAVELENGTH • MEASUREMENTS OF GAIN ON ANTENNAS IS PRESENTLY LIMITED TO 300 MHZ AND ABOVE BECAUSE WE DO NOT HAVE RELIABLE GAIN STANDARDS BELOW 300 MHZ 16

SUMMARY (CONT. ) • ANTENNA PRODUCTS WHICH PROVIDE GAIN BELOW THIS FREQUENCY ARE NOT RELIABLE; THEY MAYBE PROVIDING DIRECTIVITY VALUES (THEORETICAL) AND NOT TRUE GAIN VALUE • AT HF, LOW VHF TO HIGH VHF, ANTENNA GAIN IS MOSTLY A THEORETICAL APPROXIMATION AND NOT MEASURABLE 17

MORE INFORMATION or COPY OF PRESENTATION • SEND AN EMAIL TO THE FOLLOWING URL: atorres 4850@yahoo. com CONTACT ME AT: AL TORRES KP 4 AQI P. O. BOX 24283 DAYTON, OH 45424 -0283 18