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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

va7jw@shaw.ca

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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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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VE7NSR Topology

Blocking Horizon from NSEMO out to ~ 20 km

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VE7NSR Blocking Horizon

Grouse

SeymourCypress

Lions

Buraby Mtn

Vancouver Straits

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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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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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Worst Case, 90 Horizon

Grouseblockage

Ant pattern isimpaired forLow angle DX

Flat Terrain

DX Arrival Angle

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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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LOS – Bowen Repeater

LOS is Line Of Sight

VHF/ UHF path

Green is visible

Red is obscured

Mt Gardner

NSEMO

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LOS – Seymour Repeater

VHF – UHF Path

(actual repeater site – tower uncertain)

and for something really cool >

NSEMO

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Panoramic View - NSEMO

MicroDEM generates a panorama view that can be scrolled through 360 degrees

GrouseLionsSeymour

Eagle

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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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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