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HF SYSTEM SIMULATION TECHNIQUES by Richard P. Buckner, P. E.

HF SYSTEM SIMULATION TECHNIQUES by Richard P. Buckner, P. E. BRIEFING CONTENT. WHY SIMULATION?. SYSTEM FACTORS. SYSTEM PREDICTIONS. WHY SIMULATION?. TO UNDERSTAND PROPAGATION. Simulations are great teaching tools. TO PREDICT THE FUTURE. Contesters can see when bands will open.

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HF SYSTEM SIMULATION TECHNIQUES by Richard P. Buckner, P. E.

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  1. HFSYSTEM SIMULATION TECHNIQUESbyRichard P. Buckner, P. E.

  2. BRIEFINGCONTENT WHY SIMULATION? • SYSTEM FACTORS. • SYSTEM PREDICTIONS.

  3. WHYSIMULATION? TO UNDERSTAND PROPAGATION.Simulations are great teaching tools. • TO PREDICT THE FUTURE.Contesters can see when bands will open. • TO SAVE MONEY AND TIME.Try before Buy – simulate antennas/hardware. • BECAUSE IT’S FUN.You can work smarter in your favorite hobby.

  4. THE BIGQUESTION • What’s the Best Frequency? • HF isn’t black magic. - but some think it is. • Simulation provides the tools to optimize your HF operation.

  5. SYSTEM SIMULATION FACTORS Day-NightIonosphere GroundConductivity Solar EffectsOn Propagation Transmit Terminal: Power Coupler Loss Frequency Service Type Receive Terminal: Signal Sensitivity Bandwidth Atmospheric Noise Man-made Noise Propagation Environment: VOACAP Signal Model CCIR Atmos. Noise Model Month and Time-of-Day Required SNR & Reliability Azimuth Setting Gain Band Range Takeoff Angle Ground Terrain Tx AntennaSystem Rx AntennaSystem

  6. NEED FOR PROPAGATION PREDICTIONS Courtesy of Mr. George Lane, Lane Consultant

  7. THE TRANSMIT TERMINAL • Transmit power & losses.Use power delivered to antenna less losses. • Power variation with frequency.Compensate by varying antenna gain. • Select right antenna for each band.If directional, be sure to set azimuth. • Select correct service type.Using wrong Required SNR is a common error.

  8. THE RECEIVE TERMINAL • Know your contact.Try to specify his Tx power and antenna. • What’s the man-made noise level?Is he/she in the country or in a large city? • Accurately model distant antenna.Is it pointed at you? • If in doubt. . . .Use an Isotropic antenna with + 6 dB gain.

  9. PROPAGATION EFFECT PRIORITIES 1. Time.Always see an overview. 2. Frequency.Animate by bands. 3. SSN Level.Update monthly. W1AW Transmission Area Coverage, 20 m, May, SSB.

  10. RUN AREAS FIRST THEN ZERO IN ON CIRCUIT SNR vs. Time-of-Day SNR vs. Bands

  11. Signal or SNR? Signal (dBuV) Signal-to-Noise Ratio • Recommendation:Use signals for comparison only, and always use SNR predictions to determine circuit quality.

  12. THE EFFECT OF STATISTICS • Reliability =Time availability. • 50%Reliability.Predictions = > 15 days of month. Often used by hams. • 90%Reliability.Predictions = > 27 days of month for commercial circuits. W1AW Tx Area, 80 m, May, 24 UTC, SSB, Rel=10 to 90%.

  13. Reciprocity Effects Norfolk, VA to Iceland Iceland to Norfolk, VA • Reciprocity SNR differences can be as much as 12 dB and are due primarily to different atmospheric noise levels at the receive sites.

  14. RECEPTION AREA PREDICTIONS • Use to show potential Tx sites that can be heard from a specified receive location. • Coverage varies with noise level at receive site. Mexico City Reception Area, 80 m, May, SSB, Array Solutions 4-square Vertical Array, Az 360 dg.

  15. COMPAREANTENNA MODELS Vertical Antenna, 0 dBi gain. Array SolutionsM2 Yagi 2-stack at 40 meters,13.9 dBi gain.

  16. ANTENNA EFFECTS ON COVERAGE Array Solutions M2 Yagi 2-stack at 40 meters, 13.9 dBi gain. Vertical Antenna, 0 dBi gain. W1AW Transmission Area Coverage, 40 m, May, 24 UTC, SSB, Tx Ant Az 64 degrees.

  17. Match the AntennaTo the Prediction • Antennas that concentrate gain at low elevation angles work best when MRMs are at same angles. Array Solutions 15-m 3-stack Yagi, 18.5 dBi gain. • Try to model your own antennas whenever possible. W1AW –> Mexico City, 15 m, S-units & Elev. Ang.

  18. AREA COVERAGEUSING YAGI ARRAY • Antenna arrays with high gain can yield world- wide coverage. • Area simulations produce insight needed for best operation. W1AW to Cape Horn Area, 15 m, May, SSB, Array Solutions 3-stack Yagi Array, 18.5 dBi gain.

  19. MUF CHARTS CAN BE MISLEADING • MUF charts predict ionospheric conditions but do not account for other system variables. • SNR predictions are the most accurate measure of circuit quality.

  20. BEACONPREDICTIONS • HF beacon transmissions help to determine when the bands are open. • However, the circuit from the beacon to your station must be correctly simulated. • Always check your SSN, Reliability and antenna settings when simulating the beacon circuits.

  21. USE SNR AND REL SUMMARY CHARTS • Summary charts provide a good overview of the HF end-to-end system. They are similar to MUF charts but include all system factors. • Use summary charts to see circuit conditions at a glance. Chart concept suggested by George Lane.

  22. CONCLUSION THE SYSTEM IS THE SOLUTION™. ™Bell Telephone System Copies of this briefing may be downloaded from www.acehf.com.

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