Transcript Slide 1
Evaluating a QTH for Contesting and DXing Steve London, N2IC 1 Factors to be considered Site Selection Criteria • Ionospheric propagation to maximize QSO’s and multipliers • Relative rarity – country, state, prefix … • Antenna-friendly government and neighbors • Antenna-friendly environment • Cost of living and land • Accessibility • Availability and cost of resources for assembling station • Quiet receiving location • Proximity to non-contesting amenities and employment • Do you really want to live there ? 2 Evaluating the location What are the propagation characteristics to the desired targets ? What is the effect of local topography ? Is there an optimal, realizable antenna system for the location ? 3 A property to be considered 4 5 6 How high can that mountain be before it affects my signal ? 7 How High is that Mountain ? 4.6 degree horizon (tan-1 h/d) 8 DeLorme TopoUSA What about the curvature of the earth ? H= 2 D /1.47727 H = Number of feet that object “drops” D = Number of miles from object 9 How strong is my signal….with and without the obstruction ? 10 Case Study Denver-to-JA/UA0/JT 15 meters 0100Z March 30 Sunspot Number = 70 (Solar Flux = 120) 11 Summary of Steps Model the terrain from your QTH in the interesting directions Model your antennas over your terrain Model the propagation to your target Compare the propagation to your target with "real" terrain and "real“ antennas vs. "ideal" terrain and "ideal" antennas. 12 Model the Terrain Paper USGS Topographic Maps • Draw a line from the tower base in the direction of interest • Plot and read points along the line • Painstaking ! Topographic Map Software (i.e. DeLorme TopoUSA) • Easier, but still doesn’t automatically generate data MicroDEM (Internet Freeware and included in ARRL Antenna Book) • Manipulates Digital Elevation Model (DEM) topographic data available free on the internet. • Automatically generates azimuth terrain profile files 13 ARRL HFTA 14 Model the Antenna over Flat Terrain ARRL HFTA 15 Model the Antenna over the Actual Terrain 16 Model the Propagation 2-hop F2 Transition 3-hop F2 17 VOACAP Put it all together ! 4.6 degree horizon, 50 foot high monobander over flat terrain 18 VOACAP 1 degree horizon, 50 foot high monobander over flat terrain 19 VOACAP Compare ! 20 Conclusions Difficult to make sweeping statements based on 1 case study This single case study would suggest: - The 4.6 % obstruction significantly degrades performance to areas with marginal openings. 21 Useful References Propagation prediction software: • • • • • • VOACAP http://elbert.its.bldrdoc.gov/hf.html VOACAP Quick Guide - OH6BG http://www.uwasa.fi/~jpe/voacap/ MultiNEC (http://www.qsl.net/ac6la) ACE-HF (Reviewed Nov 2002 QST) PropMan2000 (Sept 2001 QST) WinCAP (Jan 2003 QST) Topographic map software: • DeLorme TopoUSA - http://www.delorme.com/topousa/default.asp • MicroDEM – http://www.nadn.navy.mil/Users/oceano/pguth/website/microdem.htm Terrain analysis software: • HFTA (HF Terrain Analysis) – ARRL Antenna Book, 20th edition, 22 N2IC/5 QTH … 23 24 25 26 27 What I Have Learned at the New QTH It’s easy to be moderately strong • 30’ of height works well on the high bands Not so easy to be REALLY strong • Stacked yagis play predictably on flat terrain • No apparent stacking gain on a mountain Antenna and terrain modeling doesn’t tell the whole story • HFTA has significant issues with complex terrain 28