11

Evaluating a QTH for Evaluating a QTH for Contesting and DXingContesting and DXing

Steve London, N2ICSteve London, N2IC

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Factors to be consideredFactors to be considered Site Selection CriteriaSite Selection Criteria

• Ionospheric propagation to maximize QSO’s and Ionospheric propagation to maximize QSO’s and multipliersmultipliers

• Relative rarity – country, state, prefix …Relative rarity – country, state, prefix …• Antenna-friendly government and neighborsAntenna-friendly government and neighbors• Antenna-friendly environmentAntenna-friendly environment• Cost of living and landCost of living and land• AccessibilityAccessibility• Availability and cost of resources for assembling stationAvailability and cost of resources for assembling station• Quiet receiving locationQuiet receiving location• Proximity to non-contesting amenities and employmentProximity to non-contesting amenities and employment• Do you really want to live there ?Do you really want to live there ?

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Evaluating the location Evaluating the location

What are the propagation What are the propagation characteristics to the desired characteristics to the desired targets ?targets ?

What is the effect of local topography What is the effect of local topography ??

Is there an optimal, realizable Is there an optimal, realizable antenna system for the location ?antenna system for the location ?

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A property to be A property to be consideredconsidered

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66

77

How high can that How high can that mountain be before it mountain be before it affects my signal ? affects my signal ?

88

4.6 degree horizon

(tan-1 h/d)

How High is that Mountain ?

DeLorme TopoUSA

99

What about the curvature of the earth ?What about the curvature of the earth ?

H = D2/1.47727

H = Number of feet that object “drops”

D = Number of miles from object

1010

How strong is my How strong is my signal….with and without signal….with and without

the obstruction ?the obstruction ?

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Case StudyCase Study

Denver-to-JA/UA0/JTDenver-to-JA/UA0/JT 15 meters15 meters 0100Z0100Z March 30March 30 Sunspot Number = 70 (Solar Flux = Sunspot Number = 70 (Solar Flux =

120)120)

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Summary of StepsSummary of Steps

Model the terrain from your QTH in the Model the terrain from your QTH in the interesting directionsinteresting directions

Model your antennas over your terrainModel your antennas over your terrain Model the propagation to your targetModel the propagation to your target Compare the propagation to your target Compare the propagation to your target

with "real" terrain and "real“ antennas vs. with "real" terrain and "real“ antennas vs. "ideal" terrain and "ideal" antennas."ideal" terrain and "ideal" antennas.

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Model the TerrainModel the Terrain Paper USGS Topographic MapsPaper USGS Topographic Maps

• Draw a line from the tower base in the direction of Draw a line from the tower base in the direction of interestinterest

• Plot and read points along the linePlot and read points along the line• Painstaking !Painstaking !

Topographic Map Software (i.e. DeLorme Topographic Map Software (i.e. DeLorme TopoUSA)TopoUSA)• Easier, but still doesn’t automatically generate dataEasier, but still doesn’t automatically generate data

MicroDEM (Internet Freeware and included in MicroDEM (Internet Freeware and included in ARRL Antenna Book)ARRL Antenna Book)• Manipulates Digital Elevation Model (DEM) topographic Manipulates Digital Elevation Model (DEM) topographic

data available free on the internet.data available free on the internet.• Automatically generates azimuth terrain profile filesAutomatically generates azimuth terrain profile files

1414ARRL HFTA

1515ARRL HFTA

Model the Antenna over Flat Terrain

1616

Model the Antenna over the Actual Terrain

17

2-hop F2

3-hop F2

Transition

VOACAP

Model the Propagation

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4.6 degree horizon, 50 foot high monobander over flat terrain

VOACAP

Put it all together !

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1 degree horizon, 50 foot high monobander over flat terrain

VOACAP

2020

Compare !Compare !

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ConclusionsConclusions

Difficult to make sweeping statements Difficult to make sweeping statements based on 1 case studybased on 1 case study

This single case study would suggest:This single case study would suggest:  - The 4.6 % obstruction significantly   - The 4.6 % obstruction significantly

degrades performance to areas degrades performance to areas with with marginal openings.marginal openings.

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Useful ReferencesUseful References Propagation prediction software:Propagation prediction software:

• VOACAPVOACAP http://elbert.its.bldrdoc.gov/hf.html http://elbert.its.bldrdoc.gov/hf.html• VOACAP Quick Guide - OH6BG VOACAP Quick Guide - OH6BG http://www.uwasa.fi/~jpe/voacap/http://www.uwasa.fi/~jpe/voacap/• MultiNEC (http://www.qsl.net/ac6la)MultiNEC (http://www.qsl.net/ac6la)• ACE-HF (Reviewed Nov 2002 QST)ACE-HF (Reviewed Nov 2002 QST)• PropMan2000 (Sept 2001 QST)PropMan2000 (Sept 2001 QST)• WinCAP (Jan 2003 QST)WinCAP (Jan 2003 QST)

Topographic map software:Topographic map software:• DeLorme TopoUSADeLorme TopoUSA - http://www.delorme.com/topousa/default.asp - http://www.delorme.com/topousa/default.asp• MicroDEMMicroDEM – –

http://www.nadn.navy.mil/Users/oceano/pguth/website/microdem.htmhttp://www.nadn.navy.mil/Users/oceano/pguth/website/microdem.htm

Terrain analysis software:Terrain analysis software:• HFTA (HF Terrain Analysis)HFTA (HF Terrain Analysis) – ARRL Antenna Book, 20 – ARRL Antenna Book, 20thth edition, edition,

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N2IC/5 QTH …N2IC/5 QTH …

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2525

2626

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What I Have Learned at the New QTHWhat I Have Learned at the New QTH

It’s easy to be moderately strongIt’s easy to be moderately strong• 30’ of height works well on the high bands30’ of height works well on the high bands

Not so easy to be REALLY strongNot so easy to be REALLY strong• Stacked yagis play predictably on flat terrainStacked yagis play predictably on flat terrain• No apparent stacking gain on a mountainNo apparent stacking gain on a mountain

Antenna and terrain modeling doesn’t tell Antenna and terrain modeling doesn’t tell the whole storythe whole story• HFTA has significant issues with complex HFTA has significant issues with complex

terrainterrain