1. “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 1 1

2. 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

3. 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

4. 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

5. 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

6. WAVE PENETRATION ON CONDUCTIVE MATERIAL6

7. 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
Polyethylene
Glass
Hard Rubber
1013 7 7

8. 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

9. SKIN DEPTH COMPUTER PROGRAM9

10. 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

11. COPPER TAPE WITH CONDUCTIVE ADHESIVE 11

12. COPPER TAPE CONDUCTIVE ADHESIVE WITH 1.5 MILS OF ADHESIVE12

13. MEASURING THE INDUCTANCE OF A HOME MADE INDUCTOR CONNECTED BY CONDUCTIVE TAPE13

14. ATTRIBUTES OF THE CONDUCTIVE TAPE AND COIL
The inductor is about 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

15. 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

16. MORE INFORMATION or COPY OF PRESENTATION
SEND AN TO THE FOLLOWING URL:
CONTACT ME AT:
AL TORRES
KP4AQI
P. O. BOX 24283
DAYTON, OH 16 16