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 KP4AQI EMAIL: atorres4850@yahoo.com

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

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

G= D  = (Rr + Ro) D= 4 (Ae/ 2) 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)

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 dBi (100% EFFICIENT) PRACTICAL GAIN FOR A COPPER DIPOLE IS 1.98 dBi

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

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

ANTENNA GAIN MEASUREMENTS THERE ARE TWO BASIC METHODS THAT CAN BE USED TO MEASURE ANTENNA GAIN: ABSOLUTE-GAIN AND GAIN-TRANSFER (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

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 dB (1/m) 16.5 dBi 700 V/m 3160-02 1.12 - 1.70 GHz 16.9 dB (1/m) 16.3 dBi 3160-03 1.70 - 2.60 GHz 20.6 dB (1/m) 650 V/m 3160-04 2.60 - 3.95 GHz 250 W 23.7 dB (1/m) 16.7 dBi 500 V/m 3160-05 3.95 - 5.85 GHz 27.3 dB (1/m) 3160-06 5.85 - 8.20 GHz 24° 25° 29.9 dB (1/m) 17.1 dBi 3160-07 8.20 - 12.40 GHz 33.5 dB (1/m) 16.9 dBi 3160-08 12.40 - 18.00 GHz 200 W 37.1 dB (1/m) 435 V/m 3160-09 18.00 - 26.50 GHz 50 W 40.3 dB (1/m) 16.8 dBi 220 V/m 3160-10 26.50 - 40.00 GHz 10 W 43.5 dB (1/m) 17.0 dBi 100 V/m

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 dBi), 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

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

HF YAGI ANTENNAS AND GAINS

THREE ELEMENT YAGI FOR 2 METERS CUSHCRAFT A13B2 3 Element Wideband Boomer The A13B2 is as versatile as the A17B2 is specialized. A13B2 will be your choice for high performance across the entire 2 meter band. New and experienced hams will enjoy 15.8 dBi gain on FM, packet, CW, or sideband across the 4 MHz operating range. The A13B2 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 UltraMatch balanced feed on the A13B2 provides a 50 Ohm match via a standard SO-239 UHF female connector.

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

MFJ-18522-METER YAGI, 6 EL., 144-148MHZ, WIDE BAND Our versatile new six-element MFJ-1852 2-Meter Band Spanner Yagi delivers 10-dBi gain, 20-dB 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!

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

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

MORE INFORMATION or COPY OF PRESENTATION SEND AN EMAIL TO THE FOLLOWING URL: atorres4850@yahoo.com CONTACT ME AT: AL TORRES KP4AQI P. O. BOX 24283 DAYTON, OH 45424-0283