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  • XV.
    1.SMA connector-it was done at first as means to save time and material, the idea was to connect the antennas without soldering them directly to the n-type connector where the antenna is fed but found that without the connector we had a somewhat of a better behavior, these might be because the SMA having a different diameter than the conductor produces more losses along the way.
    2.feeding point-center or side we found almost no difference by changing this parameter, still side fed disrupts the response a little bit
    3.Tuning-different pieces of materials where used to tune the antenna in order to obtain a netter response, we found out that the antenna likes brass and steel better than Al, the ideal positions to place these pieces of metal are close to the feed.
  • 2 m quagi and 70 cm helix co-located on the same boom
    Andy Haydon Park 1989 or 1990
    I made my first satellite QSO on RS-11 on Nov 18 1988
    I knew practically nothing about operation on any freq above 30 MHz and
    Absolutely nothing about satellite operation
  • 2m – 2x8 element quagis, 70cm 2x16 turn helix
    Science Museum 1990 or 1991
  • 2m 4x6 element quagi, 70cm 4x10 turn helix
    By 1993 had settled on using fibre glass stakes for booms
    Light weight rugged. These antennas still in use. Only thing done was to
    replace a few tie wraps that had deteriorated.
    The quagi elements are galvenized wire and are getting a bit rusty.
    Had to straighten a couple of elements where a crow or some large
    bird tried to sit on them.
  • 4x27 turns 23 cm array, 1.2m dish for 2.4 GHz and 2x10 turns 70cm
    Now 2001
  • This is 2003 at main street.
    Added a 13 cm helix array. 4x52 turns
    Made 102 QSO’s in mode L/S and placed 7th in Satellite operation

    1. 1. RADIATION & PROPOGATION -Broadband Antennas AJAL.A.J Assistant Professor –Dept of ECE, UNIVERSAL ENGINEERING COLLEGE, THRISSUR- 680123 - INDIA Mob: 8907305642 MAIL: ec2reach@gmail.com
    2. 2. Broadband Antennas
    3. 3. Overview Typical antennas are designed for a specific narrow band of operation Broadband antennas are designed to operate effectively over a wide range of frequencies    Public two-way-radio VHF covers 130-174Mhz Public two-way-radio UHF 406-512Mhz The challenge is to create an antenna which can operate in both the VHF and UHF bands
    4. 4. Bandwidth Definition for center frequency: f C = fU − f L 2 Bandwidth can be expressed as a percentage of the center frequency or as a ratio   The percentage is commonly used for small bandwidth antennas: f − fL BP = U × 100% fC The ratio is commonly used for large bandwidth antennas: BR = fU fL
    5. 5. Broad Spectrum of Types Helical Log Periodic Biconical Sleeve Spiral 6
    6. 6. Narrow Band Antennas Circularly Polarized Linearly Polarized Feed Horns Dipole Uniform Helical Yagi-Uda
    7. 7. Broad Band Antennas Circularly Polarized Linearly Polarized Array of narrow band antennas Tapered Helical Spiral Planar Tapered Yagi-Uda
    8. 8. Polarization helical antennas have circular polarization
    9. 9. Parameters Varied Conductor material Size of conductor
    10. 10. Cont. Parameters Varied SMA connector Tuning Feeding point
    11. 11. Biconical Antenna Types of Biconical    Infinite Biconical Finite Biconical Discone
    12. 12. Log Periodic Antenna The antenna is ideally suited for reception of VHF/UHF point-topoint communication where its directional characteristics can significantly improve rejection of interfering signals. In professional applications, this antenna is ideally suited for EMC pre-testing, surveillance and monitoring. The antenna covers a frequency range of 230 to 1600 MHz (a much wider frequency range can be received with reduced gain). http://www.winradio.com/home/ax 31b.htm
    13. 13. Sleeve Antenna The sleeve antenna is used primarily as a receiving antenna. It is a broadband, vertically polarized, omnidirectional antenna. Its primary uses are in broadcast, ship-to-shore, and ground-toair communications. Although originally developed for shore stations, there is a modified version for shipboard use. http://www.tpub.com/inch/32.ht m http://www.emartin.it/it9vky/Ris orse/opensleeve.htm
    14. 14. Spiral Antenna http://www.emi.dtu.dk/research/afg/research/gpr/spiral_antenna.html http://www.naapo.org/Argus/docs/990702.htm The spiral antenna is used primarily as a receiving antenna Vertically polarized Frequency Independent  Designed to minimize finite lengths and maximize angular dependence http://www.ece.uiuc.edu/pubs/antenna/slide03.html
    15. 15. Helical Antenna Helix antenna was invented by J. D. Kraus. two modes of operation, normal axial
    16. 16. Helix Antenna Story Dr. John Kraus Professor of Electrical Engineering and Astronomy Emeritus Ohio State University
    17. 17. Radiation Patterns NORMAL MODE
    18. 18. Radiation Patterns AXIAL MODE
    19. 19. Geometrical Considerations Matching Network S D1 D2 L
    20. 20. Building the First Prototype
    21. 21. Building the Array
    22. 22. Increasing the Diameter Kapton Tape D1 Matching Network D2
    23. 23. Calculations
    24. 24. Measurements
    25. 25. Return Loss
    26. 26. VSWR
    27. 27. Resonance and Matching Reflection     SWR Return Loss Smith Chart Impedance Transmission
    28. 28. Gain Spectrum Analyzer Signal Generator
    29. 29. Helical Antenna Directional Circularly Polarized  Polarization changes with time Both high gain and wide band
    30. 30.  1989 ONWARDS
    31. 31. 1989 Early Helix – 2 x 10 Turns
    32. 32. 1991 2 x 15 Turn 70 cm Helix
    33. 33. About 1994 AO-13 Antennas
    34. 34. 2001 AO-40 Antennas
    35. 35. 2003 13 and 23 cm Helix Arrays
    36. 36. Geometry D= diameter of helix C= circumference of helix Lo= length of one turn = C2 + S2 S ) α= pitch angle = tan ( πD −1 S= spacing between turns N= number of turns Lw= length of helix d= diameter of conductor Antenna Theory, Constantine A. Balanis Theory,
    37. 37. Normal Mode Radiation pattern similar to linear dipole The dimensions of the helix are small compared to the wavelength Narrow in bandwidth Radiation efficiency is small Rarely used
    38. 38. Axial Mode Circular Polarization    ¾<C/λ<4/3 C/λ=1:near optimum S= λ/4 Half-Power Beam width: 50 x 50 degrees 3 52λ 2 C NS Directivity: C 2S 15 N 3 λ Typical Gain: 10dB Bandwidth: 52% Frequency limit: 100MHZ to 3GHz http://www.mobile.ss.titech.ac.jp/~ken/broadband-antennas.pdf
    39. 39. Helix Applications Space Telemetry Applications of satellites, space probes, and ballistic missiles  Signals have undergone Faraday rotation Directional applications
    40. 40. Adaptation of Single Antenna for Multi-band Use.
    41. 41. Test Equipment Set Up
    42. 42. Antenna Test Range
    43. 43. Spiro-Helical Antenna
    44. 44. double helix gps antenna
    45. 45. GPS & GLONASS
    46. 46. thanks for your patient listening