“SKIN EFFECT: DO YOU NEED TO SEE A DERMATOLOGIST?” A TECHNICAL BRIEFING FOR AMATEUR RADIO OPERATORS “SKIN EFFECT: DO YOU NEED TO SEE A DERMATOLOGIST?” PRESENTED TO: ARASWF NAPLES, FL 34119 JANUARY 2018 PRESENTED BY: DR. AL TORRES KP4AQI EMAIL: atorres4850@yahoo.com 1 1

January 2018: “Skin Effect: Do you need to see a Dermatologist?” For Year 2018 January 2018: “Skin Effect: Do you need to see a Dermatologist?” February 2018: “RLC: La Familia (the Family)” or “Basics of Lightning Protection for Communication Towers” March 2018: “ Patch and PIFA Antennas: Diversity, Bandwidth, and Size ” 2

PRESENTATION OUTLINE EM Penetration Depth (Skin Effect) Definition of Skin Depth Wave penetration on conductive material Electrical Resistivity for different Materials Skin Depth for Copper at Different Frequencies Skin Depth Computer Program Copper Tape Conductive Adhesive Conductive Adhesive Experiment SUMMARY 3 3

EM PENETRATION DEPTH (SKIN EFFECT) Penetration depth is a measure of how deep light or any electromagnetic radiation can penetrate into a material It is defined as the depth at which the intensity of the radiation inside the material falls to 1/e (about 37%) of its original value at (or more properly, just beneath) the surface The concept was initially discovered by Tesla. He competed against Edison in a contest for the transmission of power at longer distances. Tesla won because Edison was using DC and the ohmic loses were greater than Tesla surface effects

DEFINITION OF SKIN DEPTH Where: δ= skin depth ρ= resistivity fo= signal frequency μr= relative permeability μo= permeability of free space = 4π x 10-7 5

WAVE PENETRATION ON CONDUCTIVE MATERIAL 6

ELECTRICAL RESISTIVITY FOR DIFFERENT MATERIALS (ohm•meter) Silver 1.59 x 10-8 Copper 1.7 x 10-8 Gold 2.2 x 10-8 Aluminum 2.8 x 10-8 Tungsten 5.6 x 10-8 Iron 10 x 10-8 Platinum 11 x 10-8 Lead 22 x 10-8 Nichrome 150 x 10-8 Carbon 3.5 x 10-5 Polystyrene 107 - 1011 Polyethylene 108 - 109 Glass 1010 - 1014 Hard Rubber 1013 7 7

SKIN DEPTH FOR COPPER AS A FUNCTION OF FREQUENCY Skin Depth (um) Skin Depth (mils) 0.5 MHz 92.2 3.6 1.0 MHz 65.19 2.55 3.5 MHz 34.84 1.37 7.0 MHz 24.64 0.96 14.0 MHz 17.42 0.68 21 MHz 14.22 0.56 28 MHz 12.32 0.48 52 MHz 9.04 0.36 146 MHz 5.39 0.21 220 MHz 4.39 0.17 450 MHz 3.07 0.12 1 GHz 2.06 0.08 2.4 GHz 1.33 0.05 8

SKIN DEPTH COMPUTER PROGRAM 9

SKIN DEPTH COMPUTER PROGRAM Computer Program lets you calculate the skin depth based on frequency, material resistivity, and material permeability (how magnetic is the material) Permeability will change the skin depth of the material. Typically, the more magnetic the material is the lower depth of penetration for the same resistivity Skin Effect Calculator Program.xls 10

COPPER TAPE WITH CONDUCTIVE ADHESIVE www.tapedepot.com 11

COPPER TAPE CONDUCTIVE ADHESIVE WITH 1.5 MILS OF ADHESIVE 12

MEASURING THE INDUCTANCE OF A HOME MADE INDUCTOR CONNECTED BY CONDUCTIVE TAPE 13

ATTRIBUTES OF THE CONDUCTIVE TAPE AND COIL The inductor is about 0.025 micro-henrys; at 146 MHz, the ohmic reactance is about 22 ohms Very little difference when the coil is connected directly to the coax (soldered) vs. the conductive tape Conductive tape is excellent for short time, temporary applications. These include testing, field day activities, and short duration experiments Conductive tape is not designed to be for permanent applications or for exposure to weather for a long time

SUMMARY WE HAVE DEFINED THE SKIN EFFECT CONCEPT (WAVE PENETRATION); SKIP THE DERMATOLOGIST! SKIN EFFECT IS A FUNCTION OF MATERIAL RESISTIVITY, FREQUENCY, AND PERMEABILITY OF THE MATERIAL (MAGNETIC PROPERTIES) AS THE FREQUENCY GOES UP, THE WAVE PENETRATION IS LESS FOR THE SAME MATERIAL RESISTIVITY (E.G. COPPER) BY USING COPPER TAPE WITH CONDUCTIVE ADHESIVE, CONNECTIONS AND CONTACTS CAN BE MADE WITHOUT THE USE OF SOLDERING 15 15

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 16 16