Terry G. Glagowski W1TR / AFA1DI

Transcription

1 The Ionogram and Radio Propagation By Terry G. Glagowski / W1TR / AFA1DI - 9/29/2017 9:46 AM Excerpts from a presentation by Tom Carrigan / NE1R / AFA1ID by Terry G. Glagowski W1TR / AFA1DI Knowledge of Radio Propagation is important to the operations of HF MARS nets. It enables the NCS to choose the proper frequency so that the net can reach the most stations. If the chosen frequency is too high, skip zones may prevent reaching close in stations. If the chosen frequency is too low, distant stations may be weak or unreadable. Radio checks on the alternative frequencies is the best indication of useable propagation. Use of Ionograms created by Digisondes can help in deciding the proper frequency. When the Internet is available, Ionograms can be viewed online at various sites.

2 Radio Propagation Ground Wave Skywave NVIS Ionosphere Layers Creation of Ionosphere D Layer: Absorption E Layer: Sporadic Es Skywave F Layers: F1, F2 Primary Skywave FoF2 Critical Frequency: NVIS MUF Maximum Useable Frequency: DX Solar Behavior 11 year Sunspot Cycles SSN SFI A Index K Index Solar Flares, CME Ionogram Digisondes generate Ionograms Interpretation of the Ionogram How to Choose Net Frequency Geography MUF and FoF2 Introduction

3 Radio Propagation Freq > MUF Maximum Frequency Reflected by Ionosphere Critical Frequency FoF2 = MUF For NVIS Freq < MUF

4 Ionospheric Layers

5 Ionospheric Layers D Layer 0-5 mhz mhz 5-10 mhz

6 Ionospheric Layers E Layer mhz

7 Ionospheric Layers F Layers

8 Ionospheric Layers Frequencies

9 Skywave Propagation Freq > MUF Freq < MUF NVIS when Skip Distance = 0, when F < FoF2 Critical Frequency

10 Solar Indices

11 Solar Indices

12 Sunspot Cycles

13 Geomagnetic A Index

14 Geomagnetic K Index

15 CME Coronal Mass Ejection

16 Solar and Geomagnetic Indices

17 Digisonde Apparatus to generate Ionograms and calculate FoF2 and MUF

18 Ionogram - Notional

19 Ionogram - Legend

20 URSI Ionospheric Parameter Codes F Layer Parameters Ionogram - Terms Parameter Description fof2 F2 layer o-mode (ordinary) critical frequency. fxf2 F2 layer x-mode (extraordinary) critical frequency. fzf2 F2 layer z-mode critical frequency. M3000F2 F2 layer M factor (the ratio of the maximum usable frequency divided by the critical frequency). h'f2 F2 layer o-mode minimum virtual height. hpf2 An estimate of the true height of the F2 layer (measurement of the ordinary mode virtual height at a frequency of 83.4% of the fof2). h'ox F layer minmum virual height of the x-mode trace at a frequency equal to the fof2. MUF3000F2 F2 layer maximum usable frequency for 3000km path. fof1 F1 layer o-mode critical frequency. fxf1 F1 layer x-mode critical frequency h'f1 F1 layer o-mode minimum virtual height. h'f F layer o-mode minimum virual height. MUF3000F1 F1 layer maximum usable frequency(see code 07). E Layer Parameters Parameter Description foe E layer o-mode critical frequency. foe2 E2 layer o-mode critical frequency (when it occurs it is between the normal E and F1 layers). h'e E layer o-mode minmum virual height. h'e2 E2 layer o-mode minimum virtual height. Es Layer Parameters Parameter Description foes Es layer hightest o-mode frequency are which a mainly continuous Es trace is observed. fxe Es layer highest x-mode frequency are which a mainly continuous Es trace is observed. fbes The blanketing frequency of layer used to derive foes. ftes Top frequency of the Es trace (any mode).

21 FoF2 Map 4 to 5 MHz

22 Ionogram - Actual FoF2 MUF F2 F2 Multiple F2 Reflections D Layer Absorption F2 FxF2 Extraordinary FoF2 FoF2 / MUF Indicate 2.5 MHz NVIS, Absorption? 3.3 MHz NVIS, Absorption? 4.6 MHz NVIS 5.8 MHz 700 KM Skip 7.6 MHz 1200 KM Skip E Layer may cause Absorption E Layer

23 How to Choose a Net Frequency Always Confirm Prediction with RADIO CHECK Before Net Region Nets Check Ionogram for FoF2 frequency Choose highest frequency <= FoF2, where there will be NO SKIP ZONE Division Nets (RGN 1,2,3) Determine the geographical region of the net operations Check the Ionogram to see what the FoF2 and skip distances will be Frequencies slightly higher than FoF2 will work somewhat due to ground wave If multiple Net Control Stations (NCS) are available then a small to moderate skip zone can be tolerated (less than 400 km) and therefore a somewhat higher frequency can be used During daytime, absorption by D and E layers can be a factor so using the highest workable frequency TransGlobal Net Choose a frequency less than the MUF for the geographical area but high enough to avoid absorption during the day by the D layer Check the Ionogram to see what the MUF, FoF2, and skip distances will be Since there will be a skip zone, multiple NCS stations will be required: West, East, and Central.

24 USAF MARS NE Division, Regions 1,2,3

25 NVIS vs DX Antennas NVIS Antenna High Angle of Radiation DX Antenna Low Angle of Radiation Vertical Low Dipole or Horizontal Loop Yagi

26 Propagation Sites A-Index, K-Index, SFI Summary CONUS HF Band Conditions NOAA Ionogram Millstone Hill Ionogram Wallops Is Ionogram Latest Ionograms Ionogram Explanation (Wikipedia) Understanding Ionograms G0LFP DX Maps Ionospheric Map Australian Space Weather Services Quick Guide to HF Propabation Using Solar Indices (N2LVI) HF Propagation Tools (N0NBH) K-Index (WikiPedia) Space Weather Prediction Center (NOAA) Space Weather (.com) Solar Ham - List of Ionosode Stations - FoF2 Map

27 Conclusion Many factors regarding solar conditions affect the ionosphere, and the magnetosphere, which affect radio propagation. Time of Day Day of Month (28 day rotation of sun) Time of Year Sunspot Cycle Solar Flares Geomagnetic Storms The best indication of good propagation is an actual radio check. Use of solar and geomagnetic indices and ionograms, can greatly aid in the choice of the best frequency for net operations.

28 Extra Slides

29 The Ionosphere The Ionosphere is a plasma shell of electrons, positive ions, and molecules that surrounds the earth The Ionosphere is created by ultraviolet radiation from the sun, which ionizes the molecules of the atmosphere Ionization is the process of ultraviolet photons transferring energy to a molecule, thereby causing the electron and the positive ion to separate Recombination is the reverse process, where a photon is emitted when an electron recombines with the positive ion randomly and spontaneously The electron density is determined by the relative ionization and recombination rates when they are in equilibrium The critical frequency is dependent on the electron density at any given region: latitude, longitude, altitude, of the ionosphere The maximum usable frequency for a given distance is dependent on the critical frequency and critical angle Factors affecting ionization include: Time of day (daylight vs darkness) Day of month (28 1/2 day solar rotation), sunspots, flares point towards or away from earth Time of year (summer vs winter vs fall and spring), amount of daylight and ionization Solar Cycle (solar flux, sunspot number) Solar Flares (unpredictable), proton and X-Ray events Solar Wind creating Geomagnetic Storms

30 Ionization and Recombination Ionization occurs with solar radiation (uv) ELECTRON NEUTRON PROTON PHOTON Photon energy is proportional to frequency, Inversely proportional to wavelength. Units are in electron volts. Energy ev = / wavelength um. Minimum energy of ultra violet wavelength Is needed to cause ionization. Ultraviolet is nm. Or ev. X-Rays have higher energy. Recombination occurs randomly, spontaneously proportional to density FREE ELECTRON ELECTRON NEUTRON PROTON FREE ELECTRON PHOTON

31 Ionospheric Layers Radio properties of the ionosphere, i.e. critical frequency, are determined by electron density, which is related to ionization rate, which depends on solar radiation.

32 Ionospheric Layers Heights

33 Multi-Hop Propagation (DX) Attenuation Proportional to Number of Hops Radiation Angle Affects DX Performance Fewer Hops

34 Multi-Path Propagation (QSB) Changing ionosphere location causes QSB fading Can be caused by magnetic storms

35 Sporadic-E VHF Propagation Also sometimes on 28 mhz and 144 mhz

36 Ionogram - Actual FoF2 MUF F2 Multiple F2 Reflections D Layer Absorption F2 FoF1 FoF2 Es Layer FoF2 / MUF Indicate 2.5 MHz NVIS, Absorption? 3.3 MHz NVIS 4.6 MHz NVIS 5.8 MHz 600 KM Skip 7.6 MHz 1100 KM Skip E Layer Small Skip Distance

37 Solar and Geomagnetic - Actual

38 Ionogram - Actual FoF2 MUF D Layer Absorption FoF2 / MUF Indicate 2.5 MHz NVIS, Absorption Low? 3.3 MHz NVIS, Absorption Low? 4.6 MHz NVIS 5.8 MHz NVIS 7.6 MHz 900 KM Skip E Layer may cause Absorption Es Layer E Layer Skip Distance

39 Ionogram - Actual Austin not NE FoF2 MUF F2 F2 Multiple F2 Reflections Es E FxF2 Extraordinary D Layer Absorption FoF2 Es Layer E Layer FoF2 / MUF Indicate 2.5 MHz NVIS, Absorption High? 3.3 MHz NVIS, Absorption High? 4.6 MHz NVIS, Absorption High? 5.8 MHz NVIS 7.6 MHz 500 KM Skip E Layer may cause Absorption

40 Ionogram - Actual FoF2? Es Layer MUF? D Layer Absorption? Very Few F Layer Reflections Insufficient Data for Digisonde to Calculate FoF2 and MUF E Layer may be blocking Es Layer Skip Distance?

41 Ionogram - Actual FoF2?? Es Layer MUF? Es D Layer Absorption 6 Meters Open? FoF2 / MUF Indicate 2.5 MHz NVIS, Absorption High? 3.3 MHz NVIS, Absorption High? 4.6 MHz NVIS, Absorption High? 5.8 MHz NVIS?, Short Skip, Long Skip, Some Attenuation 7.6 MHz 500 KM Skip? E Layer may cause Absorption and Short Skip Es Es Multiple Es Reflections Es Layer Skip Distance?

42 Ionogram - Actual FoF2 Es Layer MUF Es D Layer Absorption FoF2 / MUF Indicate 2.5 MHz NVIS, Absorption High? 3.3 MHz NVIS, Absorption High? 4.6 MHz NVIS, Absorption High? 5.8 MHz 500 KM Skip, Short Skip, Some Attenuation 7.6 MHz 1100 KM Skip? E Layer may cause Absorption and Short Skip Es Es Multiple Es Reflections Es Layer Skip Distance?

43 Ionogram - Actual FoF2 MUF F2 F2 Multiple Reflections D Layer Absorption FoF2 E Layer FoF2 / MUF Indicate 2.5 MHz NVIS, Absorption High? 3.3 MHz NVIS, Absorption High? 4.6 MHz NVIS 5.8 MHz 600 Skip E Layer may cause Absorption

44 NVIS Near Vertical Incident Skywave Typical NVIS Range Typical Ground Wave Range Courtesy: Tom Carrigan / NE1R / AFA1IR

45 Ionospheric Layers Resonant (Critical) frequency determined by electron density

46 Ionospheric Layers Resonant (Critical) frequency determined by electron density

47 Ionospheric Layers

48 Ionospheric Layers

49 Ionospheric Layers

50 Ionospheric Layers

51 Skywave Propagation NVIS when Skip Distance = 0, when F < FoF2

52 Sunspot Cycles

53 Sunspot Cycles