HF OPERATORS
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HIGH FREQUENCY TERRAIN ASSESSMENT
HFTA and MicroDEM
by
John White
VA7JW
va7jw@shaw.ca
8 Oct 2014 Rev 1
NSARC HF Operators
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What is HFTA ?
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 Antenna modeling software (i.e. EZNEC) typically models over
FLAT TERRAIN
 The physical features of the land at your QTH will alter the flat
terrain vertical radiation pattern model
 HFTA software models the vertical radiation pattern of your
antenna based on your actual terrain
ACTUAL TERRAIN
ALL DIRECTIONS = 360 degrees
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Where to Get HFTA?
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HFTA is ARRL proprietary software supplied on a CD which is
included with every ARRL antenna handbook since 2003
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It cannot be purchased from ARRL as a stand-alone package
nor be downloaded for the web
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HFTA was developed by Dean Straw N6VB while employed at
ARRL as Senior Technical Editor for many publications
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Copy the HFTA files to your PC from the CD
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Runs under Windows XP and Win 7
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HFTA Features
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 HFTA allows experimentation with different antennas at different
heights to characterize a given installation, or optimize and
design a new installation, at a given location / terrain
 Computes horizontally polarized radiation, sorry - no verticals
 Dipoles and yagi’s from 2 elements to 6 elements
 Heights > 1 foot above ground, at antenna site
 Bands from 160 through 10 meters
 Shows only low angle radiation < 34 degrees (why later ..)
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Vertical Radiation Plots
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 Example: Vertical elevation plot – dipole - 1 wavelength high
over flat terrain
 Lobes show angles of maximum gain and minimum gain,
(peaks and nulls)
 Loss effect of real ground is also noted
Second Null at 90 degrees
Perfect Ground
Second Lobe at 50 degrees
Average Earth Ground
First Null at 30 degrees
Max Lobe at 15 degrees
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Effect of Terrain
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 Recombination of the Direct wave and ground Reflected wave
determines the angle at which max and min lobes appear
 Higher the antenna, the lower becomes the first maximum lobe
with more lobes developing with increased height
 The angles of reflection are also determined by
 the distance from the antenna to terrain variations
 the angle of the terrain to the antenna – rising, falling, flat …
 rising ground will increase low angle, falling will decrease low angle
15 degrees
8 Oct 2014 Rev 1
10 degrees
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5 degrees
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How Lobes are Formed
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 Lobes occur due to the phase re-enforcement or cancellation
of the direct wave from the antenna and the reflected wave
from the ground
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(Reflected wave undergoes a 180 deg phase shift since E field must = 0 at t he surface of a conductor,
i.e the ground)
Formation of a Max Lobe at 50 deg
Formation of a Null at 30 deg
Nulled Wave Front
at 30 degrees
In Phase Wave Front
Lobe at 50 degrees
50 deg
30 deg
ANTENNA
ANTENNA
One Wavelength High
One Wavelength High
Ground
Ground
Antenna Image
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180 degree Phase Shift of
Reflected E field
Antenna Image
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180 degree Phase Shift
of Reflected E field
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Where’s the Terrain Info?
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 HFTA does not contain terrain / topographical information
 HFTA uses a digital topographical mapping application which
renders topographical information into a file format suitable for
use by HFTA
 MicroDEM is the companion mapping software that provides
HFTA with the required land profiles for mapping
 More on MicroDEM later ….
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HFTA – What will it do?
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Enter the Type and Height of your antenna above ground
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Enter Frequency
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Enter the geographical definition of your terrain from MicroDEM
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HFTA will calculate the terrain profile every 5 degrees around
your QTH out to 4400 m / 14,500 feet
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HFTA will plot the vertical angle of radiation of the antenna,
 can be compared to flat ground performance
 can be compared to the arrival of low angle DX signals
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Main HFTA Window
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Enter Frequency
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Terrain Files
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 as generated by MicroDEM
are loaded here
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Ant Type
 select the antenna from
a drop down menu
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Height of Antenna – type in
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There are 4 fields so that 4 models can be compared
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Completed Window
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MicroDEM has generated
a profile at a 60 deg AZ
from my QTH. 3 element
yagi at 60 ft, all entered
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Loaded the Flat File that
plots patterns of flat terrain
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Checked both lines 1 and 4
to plot pattern of same graph
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Terrain Profile Plot
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 Hit the
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Height of Antenna above ground
Ground (Terrain) Profile at
60 degrees Azimuth
Burrard Inlet – Sea Level
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Burke Mtn Ridge
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Vertical Radiation Plots
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 Hit the
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Button
Antenna Pattern
Flat Terrain Pattern
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Typical Gain over Flat
about 4 to 6 dB out to
20 deg. The Negative
Profile advantage
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No advantage 14 to 18 degrees
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Sharp nulls at 8 & 23 deg
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One would experiment with various heights to find optimum performance
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DX Low Angle Skip
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 Many DX signals arrive at low angles due to long skips
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 Long skip typically arrives at < 34 degrees
(ARRL Antenna Handbook 21st edition, pages 3-21 ff)
 Antenna performance for low angle / long skip of particular
interest to DX operators
 HFTA allows for examination of low angle arrivals with respect
to the vertical elevation antenna plot
 Enter desired angle coverage in HFTA window.
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DX Profile Files
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 HFTA is supplied with files (.PRN) that provide a statistical angle
of arrival of DX signals as a percentage of time that can be
plotted along with the vertical radiation pattern
 Select your call zone i.e. VE7 from the .PRN file listing
 Areas are Africa (AF), South Asia (AS), Europe (EU), Far East
(JA), South Pacific (OC), South America (SA), and the US
 Select the DX “area” from the list of VE7 files by clicking in the
Elevation field of HFTA
 The PRN elevation file is entered in to
the HFTA main window
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The Complete Plot
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 Introduce the EU file for
DX angle of arrival
 Bar graph representation
 Most often, signals arrive
between 3 and 6 degrees
 Antenna pattern happens to
peak in this area – that’s good
 Try other bands, directions
 That’s it! except for the mapping ….
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Maps and MicroDEM
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 MicroDEM software loads and displays digital topographical
maps
 Digital topographical map is called a DEM = Digital Elevation
Module (Digital Elevation Map makes more sense)
 DEM’s are 3 dimensional topographical providing latitude,
longitude and elevation
 Canada and US DEM’s are available on the web and are free
 MicroDEM processes these maps & provides HFTA with terrain
files that allows HFTA to plot the profiles and calculate the
vertical radiation patterns
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Where to Get MicroDEM?
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MicroDEM is downloadable from the web, free
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Do NOT download the MicroDEM version from the ARRL CD. It
is out of date
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Developed by Professor Peter Guth of the US Naval Academy
http://www.usna.edu/Users/oceano/pguth/website/microdem/microdem.htm
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The latest MicroDEM version is now 64bit
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Runs under Windows XP and Win 7
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About MicroDEM
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 MicroDEM is a powerful and complex application
 Do not “experiment” with it as setup is critical
 Recommend downloading “Beginners Guide to HFTA” for setup
directions and settings to get started
http://www.nsarc.ca/tech_archive/Articles/hfta.pdf
 Also download “Operating Instructions for HFTA Ver 1.04” by Dean
Straw, dated 22 Feb 2013,
http://www.arrl.org
 or go to the ARRL website, search for HFTA, click on HFTA …
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Canadian DEM’s
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 Access DEMS at http://www.geobase.ca
 Geobase > data > digital elevation data
 Whole Canada map
 Select General Region
 i.e. South West Canada, Region 92
 Click on 92 to expand
 Region 92 is subdivided
 Select Vancouver is 092G
 Click to expand again
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Expanded DEM
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 DEM now shows districts within 092G
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 Click on the NAME closest to QTH
 This case Port Coquitlam (PoCo)
 Data field below map shows selected
DEM file(s) for download
 092G07 is the DEM file for PoCo
 This is downloaded to a directory set up by HFTA
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Sub-DEM Structure
(Canadian only)
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 Sub sections within 092G are identified by suffixes 01 thru 08 with
attached names as shown. Each sub section has an East and West
map i.e. demw – DEM west and deme = DEM east
LOWER MAINLAND DEM MAP LIMITS
Fraser Valley
GVRD
West – North Van
VA7JW
Stave -Mission
49.5
092G06
North Van
LATITUDE
092G05
N
demw
092G07
PoCo
deme
demw
092G08
Stave
deme
demw
092H05
Harrison
deme
49.25
092G04
N
092G03
Lulu Island
demw
092G02
New West
deme
demw
092H04
Chilliwack
092G01
Mission
deme
demw
deme
49.0
124.0
123.5
123.0
122.5
122.0
121.5
LONGITUDE
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MicroDEM Appearance
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Main window
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This is a map of
the lower mainland, a
composite of 8 DEM’s
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North shore Mtns
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Harbour
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Vancouver
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New Westminster
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Surrey
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Richmond, Delta, Ladner
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Opening the DEM’s
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 Refer to Beginners Guide for unzipping and saving the file
 When DEM file has been selected, open in MicroDEM
 First time may take a moment to interpret
 Display is set to represent elevation
by color. Blue ~ sea level, red ~ 2000m
 Resolution looks miserable but it is not
 Magnification can show great detail
 MicroDEM will stitch together maps to
make larger maps i.e. lower main land
VA7JW QTH
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Where Am I ?
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 You have to know where you are located, accurately
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 Use Google Earth (suggest version 7.1.1.1888 or later)
 Enter your street address in the SEARCH field
 Magnify and find your house
 Zoom in and place cursor on top of your antenna / tower
 Lower right, read off your Latitude. Longitude and Elevation
i.e. 49 degrees 16 minutes 59.73 seconds North etc., EXACTLY (why?)
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Position Accuracy
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 Profile plots and antenna pattern accuracy are based on
position of antenna / tower on the map. Get within 10 ft.
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 Distances between Latitudes are constant North to South
 Distance between Longitudes varies with Latitude North and
South of equator > becomes zero at Poles
 Table shows uncertainty of location at equator; E-W error
becomes less at higher latitudes.
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Find QTH on the Map
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 Write down the Google Earth coordinates
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 Open up your MicroDEM QTH map
 Mouse over estimated QTH
 Watch bottom of MicroDEM window
for Lat, Long and Elev readings
 Move mouse until Lat Long read
~ same as Google Earth Lat & Long
 That’s your QTH (VA7JW)
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Enter QTH in MicroDEM
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 Double Click on your QTH
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 Window appears with Lat and
Long of the mouse on map
 This does not have to be
precisely set on the map
 Now enter the exact Lat and Long
as per Google Earth in the fields
 MicroDEM now knows exactly where your antenna is
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FAN Generation
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 MicroDEM, will generate a land profile, radially from the QTH,
every 5 degrees, over 360 degrees, out to 4400 meters
 This “suite” of files is referred to as a FAN
 Each 5 degree profile is saved as a .PRO file
 There is one file for each 5 degree increment (71 in total)
 This is the field that will populate the HFTA window under the
Terrain Files field
(MicroDEM saves these files automatically as degrees (i.e. VA7JW-60.00.PRO)
Suggest renaming with date & time stamp i.e. VA7JW-21jun13-1708-60.00.PRO)
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HFTA is READY
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 You can now run HFTA to do your site analysis
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 Run profiles
 Run antenna patterns
 There are other very important, useful features in MicroDEM
 MicroDEM will plot,
 The Blocking Horizon
 Topology coverage map
 Lines of Sight, useful for VHF/ UHF
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The Blocking Horizon
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 The horizon limits the ultimate angle for blockage of signal, both
on transmit and receive
 MicroDEM will graph the blocking horizon
 Line of Sight – your QTH to the horizon in terms of vertical angle
as well as distance to the blockage vs. azimuth
 Horizon Blocking Plots
 Elevation plot to blocking horizon, over 360 degrees
 Distance plot to the blocking horizon, over 360 degrees
 Topographical MAP showing areas where blockage occurs
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VE7NSR Example
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 A Topographical map showing blocking horizon
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 The Vertical elevation plot to the horizon, in degrees
 can also run distance to blocking horizon
 Reveals problematic areas as well as good areas, by Azimuth
 Plot profiles in directions of interest as well as worst & best
 Take into account antenna beam width with respect to coverage
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VE7NSR Topology
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 Blocking Horizon from NSEMO out to ~ 20 km
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VE7NSR Blocking Horizon
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Lions
Grouse
Seymour
Cypress
Buraby Mtn
Vancouver
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Straits
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VE7NSR, the HFTA Plots
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 PRO files generated
 Freq 14.2 MHz
 PRO file at 1200, 3 ele
yagi at 70ft entered
 Flat Terrain file
 DX Rx angles
.PRN files
for South America
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Typical 2 Degree Horizon
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 North Van platform
at 120 degrees
 Land profile drops,
looking up Burrard
inlet towards Bby Mtn
 Actual is not as
good as Flat
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Worst Case, 90 Horizon
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 Grouse
blockage
 Ant pattern is
impaired for
Low angle DX
 Flat Terrain
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DX Arrival Angle
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Best Case, 00 Horizon
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 Negative Horizon,
ground slopes
away at 2500
 Ant pattern
excellent
 No blockage of
low angle sig
arrival. Good for DX
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LOS – Bowen Repeater
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 LOS is Line Of Sight
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 VHF/ UHF path
 Green is visible
 Red is obscured
Mt Gardner
NSEMO
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LOS – Seymour Repeater
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 VHF – UHF Path
(actual repeater site – tower uncertain)
NSEMO
 and for something really cool >
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Panoramic View - NSEMO
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 MicroDEM generates a panorama view that can be scrolled
through 360 degrees
Lions
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Grouse
Seymour
Eagle
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DONE
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 Once the PRO(files) are generated, HFTA is ready to compute
 Characterize your location
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all antennas (horizontally polarized only)
all heights
all bands
all directions
 Vancouver has a complex horizon - good and no so good for DX
 plot your horizon as shown slide 34
 know which parts of the world are at what azimuth, slide 34
 blockages mean low angle will be impaired but under most
openings, higher angle is common and DX will be worked
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Summary
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 HFTA and MicroDEM will provide a characterization of your
antenna vertical radiation patterns as altered by local terrain at
your QTH
 HFTA software is easy to use
 MicoDEM mapping software takes effort to setup
 To make this task EASIER download “Beginners Guide to HFTA
and Microdem” at:
http://www.nsarc.ca/tech_archive/Articles/hfta.pdf
 Provides step x step instructions
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