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Small 500 KHz Transmitting Antennas VE3KL

Small 500 KHz Transmitting Antennas VE3KL. Top Hat. Insulated Base. Vertical 500 KHz Antenna….. Courtesy (Gunnar SM6BGP) Height = 30 metres R (antenna) = 22 Ohms ….. measured. Acknowledgements. OARC, RAC and Bryan (VE3QN) Industry Canada..Justine Sider (computer use)

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Small 500 KHz Transmitting Antennas VE3KL

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  1. Small 500 KHz Transmitting AntennasVE3KL Top Hat Insulated Base Vertical 500 KHz Antenna….. Courtesy (Gunnar SM6BGP) Height = 30 metres R (antenna) = 22 Ohms ….. measured David Conn VE3KL

  2. Acknowledgements OARC, RAC and Bryan (VE3QN) Industry Canada..Justine Sider (computer use) Gunnar….SM6BGP….Permission to use material from Web site RIK..ON7YD……permission to use diagrams from Web site STAR-H Corp….a patented novel short AM monopole with high radiation resistance.. the author wishes to thank STAR-H for permission to experiment with this antenna (non-commercial use) 10/15/2014 David Conn VE3KL 2

  3. Many Possible Antenna Types Gunnar….SM6BGP N Monopoles Separately Fed Closely Spaced STAR-H Patent 10/15/2014 David Conn VE3KL

  4. Presentation Outline Basics..Radiation Resistance, Efficiency, Bandwidth Vertical Antennas Inverted L Antenna Loop Antennas Other types including the Horizontal Dipole Bibliography 10/15/2014 David Conn VE3KL 4

  5. Design Issues(Small Antennas) Radiation Resistance Bandwidth Efficiency Big Antennas {All of above increase} 10/15/2014 David Conn VE3KL 5

  6. Design Issues(Small Antennas) Low Radiation Resistance Low Efficiency Narrow Bandwidth Space Limitations…….600 metre λ Simulation Problems….NEC4 needed 10/15/2014 David Conn VE3KL 6

  7. Radiation Resistance, RrDefinition Prad = Io2Rr/2 [Watts] Prad = Power radiated from an antenna I = IoCos(2πft) Rr for a halfwave dipole = 73 Ohms 10/15/2014 David Conn VE3KL 7

  8. Antenna Efficiency Rr = radiation resistance…….Rloss = loss resistance Example: Rrad = 0.5 Ohms, Rloss = 22 Ohms Efficiency = 0.5/22.5 = 0.022 = 2.2% (-17dB) 10/15/2014 David Conn VE3KL 8

  9. Antenna Efficiency Efficiency = Rr/Rloss (for small Rr) Doubling Rr doubles the antenna efficiency Designers work this issue 10/15/2014 David Conn VE3KL 9

  10. Antenna Bandwidth SWR B 2.0 1.0 • Several ways to define Bandwidth: 3 dB, SWR, Return Loss • Calculated from Antenna Equivalent Ciruit • Can be very small ( 1 KHz ) for small antennas Example B = 4 KHz for SWR =2:1 Frequency 10/15/2014 David Conn VE3KL 10

  11. Vertical Antennas Basics…applies to all antennas Vertical Antenna No Top Hat, Top Hat Case study of a vertical monople with top hat…SM6BGP Vertical Cage Type Antenna 10/15/2014 David Conn VE3KL 11

  12. Top Hat Current Current L L Ground Short Vertical Monopoles with and without a Top Hat. Top Hat forces current to be nearly uniform along antenna. Radiation resistance increased with a Top Hat. Short Vertical Monopoles Base Fed 10/15/2014 David Conn VE3KL 12

  13. Monopoles Receive Equal Power D Top View Monopole Side View L Voltage Source Ground Star-H Vertical Cage Concept Similar to Folded Dipole Closely Spaced Big Increase in Rr, B and efficiency 10/15/2014 David Conn VE3KL 13

  14. Radiation ResistanceBasic Vertical Elements Short Current Element….basic element Short Vertical Monopole…no top hat Short Vertical Monopole…ideal top hat 10/15/2014 David Conn VE3KL 14

  15. Radiation Resistance (Rr)Basics…..Short Current Element IoCOS(2πfot) L metres long PowerRadiated = Io2Rr/2 [Watts] 10/15/2014 David Conn VE3KL 15

  16. Radiation Resistance (Rr)Short Current Element..ExampleL/λ = 0.05 Io = 5.0 Amp IoCOS(2πfot) 30 metres long Rr = 2 [Ohms] PowerRadiated = Io2Rr/2 = 25 [Watts] 10/15/2014 David Conn VE3KL 16

  17. Short Vertical MonopoleA Simple Basic Antenna L/λ = 0.05 L= 30 metres @500 KHz H=L Current varies linearly on antenna Many Ground Radials Rr = 1.0 Ohm 10/15/2014 David Conn VE3KL 17

  18. Short Vertical MonopoleCapacitanceL/λ = 0.05, L=30 m H = L L = length [m] d = wire diameter[m] Cv in pF Example fo = 500 KHz L = 30 m, d = 0.001m: Cv = 158 pF Xo = 1/(2πfoCv) = 2015 Ohms 10/15/2014 David Conn VE3KL 18

  19. Antenna Efficiency ON7YD Diagram Short Vertical Monopole Current varies linearly on antenna Rrad = 1.0 Ohm, Rloss = 22 Ohms Efficiency = 1./22 = 0.045 = 4.5% (-13 dB) 10/15/2014 David Conn VE3KL 19

  20. SWR B 2.0 1.0 Antenna Bandwidth Vertical Antennas(Radio Definition…SWR based) Antenna Transformer Loading Coil Cv Rr +Rloss SWR Bandwidth: Frequency range between specified SWR level SWR =1.0 @ fo fo 10/15/2014 David Conn VE3KL 20

  21. Antenna BandwidthVertical Antennas(Radio Definition…SWR based) • B is the Bandwidth • R is the input resistance of the antenna [Ohms] • Xo is the input reactance of the antenna [Ohms] • fo is the operating frequency • SWR is the maxiumum permissible SWR Example: SWR = 2:1, R = 22, Xo = 2015, fo = 500 KHz B = 3.8 KHz……. Very low….poor for high speed data communictions 10/15/2014 David Conn VE3KL 21

  22. Bandwidth.. Vertical No Top Hat Example: Vertical Antenna No Top Hat Height = 0.05 wavelengths SWR = 2.0 Rantenna = 22 Ω Xo = 2015 Ω BW = 3.8 KHz Our Range 10/15/2014 David Conn VE3KL 22

  23. Summary Vertical No Top Hat fo = 500 KHz L = 30 metres Max. SWR = 2:1 Rr = 1.0 Ohms Rloss = 21 Ohms……based on measurements of SM6BGP Efficiency = 1/22 = 0.045 = 4.5% (-13 dB) BW = 3.8 KHz 10/15/2014 David Conn VE3KL 23

  24. Short Vertical Monopole with Top Hat Analysis for one Top Hat Element Generally many are used 10/15/2014 David Conn VE3KL 24

  25. Short Vertical Monopole with Top HatRadiation Resistance Four times that of the Vertical With no top hat Rr = 4.00 Ohms for 30 metre high antenna with ideal top hat 10/15/2014 David Conn VE3KL 25

  26. Example: 10/15/2014 David Conn VE3KL 26

  27. Example: 10/15/2014 David Conn VE3KL 27

  28. Example: 10/15/2014 David Conn VE3KL 28

  29. The Future • Much more software integration needed • link measurement tools to all software • include data base output for all software • use Excel and SQLite data bases • standard data base file format • Models, especially ground types need improvement • Much more work on optimization • Electrical design to mechanical drawing needed for Microwave Antennas • 2010 Antenna design tools similar to Silicon IC design in its infancy

  30. Summary VY 73 Dave VE3KL

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