- - - - - - - - - - - nsarc hf operators18 oct 2014 rev 1 hf operators high frequency terrain...
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NSARC HF Operators 18 Oct 2014 Rev 1
HF OPERATORS
HIGH FREQUENCY TERRAIN ASSESSMENT
HFTA and MicroDEM
by
John White
VA7JW
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NSARC HF Operators 28 Oct 2014 Rev 1
What is HFTA ?
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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NSARC HF Operators 38 Oct 2014 Rev 1
Where to Get HFTA?
HFTA is ARRL proprietary software supplied on a CD which is included with every ARRL antenna handbook since 2003
It cannot be purchased from ARRL as a stand-alone package nor be downloaded for the web
HFTA was developed by Dean Straw N6VB while employed at ARRL as Senior Technical Editor for many publications
Copy the HFTA files to your PC from the CD
Runs under Windows XP and Win 7
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NSARC HF Operators 48 Oct 2014 Rev 1
HFTA Features
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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NSARC HF Operators 58 Oct 2014 Rev 1
Vertical Radiation Plots
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
First Null at 30 degrees
Max Lobe at 15 degrees
Second Null at 90 degrees
Perfect Ground
Average Earth Ground
Second Lobe at 50 degrees
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NSARC HF Operators 68 Oct 2014 Rev 1
Effect of Terrain
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 degrees10 degrees 5 degrees
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NSARC HF Operators 78 Oct 2014 Rev 1
How Lobes are Formed
Lobes occur due to the phase re-enforcement or cancellation of the direct wave from the antenna and the reflected wave from the ground
(Reflected wave undergoes a 180 deg phase shift since E field must = 0 at t he surface of a conductor, i.e the ground)
180 degree Phase Shiftof Reflected E field
Ground
Nulled Wave Frontat 30 degrees
One Wavelength High
ANTENNA
Antenna Image
30 deg
Formation of a Max Lobe at 50 deg Formation of a Null at 30 deg
50 deg
Antenna Image
Ground
180 degree Phase Shift of Reflected E field
In Phase Wave FrontLobe at 50 degrees
One Wavelength High
ANTENNA
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NSARC HF Operators 88 Oct 2014 Rev 1
Where’s the Terrain Info?
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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NSARC HF Operators 98 Oct 2014 Rev 1
HFTA – What will it do?
Enter the Type and Height of your antenna above ground
Enter Frequency
Enter the geographical definition of your terrain from MicroDEM
HFTA will calculate the terrain profile every 5 degrees around your QTH out to 4400 m / 14,500 feet
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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NSARC HF Operators 108 Oct 2014 Rev 1
Main HFTA Window
Enter Frequency
Terrain Files as generated by MicroDEM
are loaded here
Ant Type select the antenna from
a drop down menu
Height of Antenna – type in
There are 4 fields so that 4 models can be compared
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NSARC HF Operators 118 Oct 2014 Rev 1
Completed Window
MicroDEM has generateda profile at a 60 deg AZfrom my QTH. 3 elementyagi at 60 ft, all entered
Loaded the Flat File thatplots patterns of flat terrain
Checked both lines 1 and 4to plot pattern of same graph
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NSARC HF Operators 128 Oct 2014 Rev 1
Terrain Profile Plot
Hit the Button
Height of Antenna above ground
Ground (Terrain) Profile at 60 degrees Azimuth
Burrard Inlet – Sea Level Burke Mtn Ridge
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NSARC HF Operators 138 Oct 2014 Rev 1
Vertical Radiation Plots
Hit the Button
Typical Gain over Flat about 4 to 6 dB out to 20 deg. The Negative Profile advantage
No advantage 14 to 18 degrees
Sharp nulls at 8 & 23 deg
One would experiment with various heights to find optimum performance
Antenna Pattern
Flat Terrain Pattern
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NSARC HF Operators 148 Oct 2014 Rev 1
DX Low Angle Skip
Many DX signals arrive at low angles due to long skips
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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NSARC HF Operators 158 Oct 2014 Rev 1
DX Profile Files
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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NSARC HF Operators 168 Oct 2014 Rev 1
The Complete Plot
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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NSARC HF Operators 178 Oct 2014 Rev 1
Maps and MicroDEM
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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NSARC HF Operators 188 Oct 2014 Rev 1
Where to Get MicroDEM?
MicroDEM is downloadable from the web, free
Do NOT download the MicroDEM version from the ARRL CD. It is out of date
Developed by Professor Peter Guth of the US Naval Academy
http://www.usna.edu/Users/oceano/pguth/website/microdem/microdem.htm
The latest MicroDEM version is now 64bit
Runs under Windows XP and Win 7
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NSARC HF Operators 198 Oct 2014 Rev 1
About MicroDEM
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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NSARC HF Operators 208 Oct 2014 Rev 1
Canadian DEM’s
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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NSARC HF Operators 218 Oct 2014 Rev 1
Expanded DEM
DEM now shows districts within 092G
Click on the NAME closest to QTH
This case Port Coquitlam (PoCo)
Data field below map shows selectedDEM 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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NSARC HF Operators 228 Oct 2014 Rev 1
Sub-DEM Structure(Canadian only)
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
123.5 123.0 122.5 122.0 121.5
49.0
49.25
49.5
092G06North Van
092G07PoCo
092G08Stave
092H05Harrison
092G03Lulu Island
092G02New West
092G01Mission
092H04Chilliwack
Fraser Valley
GVRD
VA7JW
092G05N
092G04N
West – North Van
Stave -Mission
124.0
demw demedemw deme demw deme
demw deme demw deme demw deme
LONGITUDE
LAT
ITU
DE
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NSARC HF Operators 238 Oct 2014 Rev 1
MicroDEM Appearance
Main window
This is a map ofthe lower mainland, acomposite of 8 DEM’s
North shore Mtns
Harbour
Vancouver
New Westminster
Surrey
Richmond, Delta, Ladner
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NSARC HF Operators 248 Oct 2014 Rev 1
Opening the DEM’s
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 elevationby color. Blue ~ sea level, red ~ 2000m
Resolution looks miserable but it is not
Magnification can show great detail
MicroDEM will stitch together maps tomake larger maps i.e. lower main land
VA7JW QTH
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NSARC HF Operators 258 Oct 2014 Rev 1
Where Am I ?
You have to know where you are located, accurately
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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NSARC HF Operators 268 Oct 2014 Rev 1
Position Accuracy
Profile plots and antenna pattern accuracy are based on position of antenna / tower on the map. Get within 10 ft.
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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NSARC HF Operators 278 Oct 2014 Rev 1
Find QTH on the Map
Write down the Google Earth coordinates
Open up your MicroDEM QTH map
Mouse over estimated QTH
Watch bottom of MicroDEM windowfor 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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NSARC HF Operators 288 Oct 2014 Rev 1
Enter QTH in MicroDEM
Double Click on your QTH
Window appears with Lat andLong 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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NSARC HF Operators 298 Oct 2014 Rev 1
FAN Generation
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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NSARC HF Operators 308 Oct 2014 Rev 1
HFTA is READY
You can now run HFTA to do your site analysis 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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NSARC HF Operators 318 Oct 2014 Rev 1
The Blocking Horizon
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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NSARC HF Operators 328 Oct 2014 Rev 1
VE7NSR Example
A Topographical map showing blocking horizon
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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NSARC HF Operators 338 Oct 2014 Rev 1
VE7NSR Topology
Blocking Horizon from NSEMO out to ~ 20 km
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NSARC HF Operators 348 Oct 2014 Rev 1
VE7NSR Blocking Horizon
Grouse
SeymourCypress
Lions
Buraby Mtn
Vancouver Straits
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NSARC HF Operators 358 Oct 2014 Rev 1
VE7NSR, the HFTA Plots
PRO files generated
Freq 14.2 MHz
PRO file at 1200, 3 eleyagi at 70ft entered
Flat Terrain file
DX Rx angles .PRN filesfor South America
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NSARC HF Operators 368 Oct 2014 Rev 1
Typical 2 Degree Horizon
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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NSARC HF Operators 378 Oct 2014 Rev 1
Worst Case, 90 Horizon
Grouseblockage
Ant pattern isimpaired forLow angle DX
Flat Terrain
DX Arrival Angle
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NSARC HF Operators 388 Oct 2014 Rev 1
Best Case, 00 Horizon
Negative Horizon,
ground slopes
away at 2500
Ant pattern
excellent
No blockage of
low angle sig
arrival. Good for DX
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NSARC HF Operators 398 Oct 2014 Rev 1
LOS – Bowen Repeater
LOS is Line Of Sight
VHF/ UHF path
Green is visible
Red is obscured
Mt Gardner
NSEMO
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NSARC HF Operators 408 Oct 2014 Rev 1
LOS – Seymour Repeater
VHF – UHF Path
(actual repeater site – tower uncertain)
and for something really cool >
NSEMO
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NSARC HF Operators 418 Oct 2014 Rev 1
Panoramic View - NSEMO
MicroDEM generates a panorama view that can be scrolled through 360 degrees
GrouseLionsSeymour
Eagle
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NSARC HF Operators 428 Oct 2014 Rev 1
DONE
Once the PRO(files) are generated, HFTA is ready to compute
Characterize your location 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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NSARC HF Operators 438 Oct 2014 Rev 1
Summary
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