6192009

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• Presented by
• Clackamas Amateur Radio Emergency Services (CARES)

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NVIS

• Near Vertical Incident Skywave

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Introduction

• In this class the basic techniques in the
  theory, use, and making of a NVIS antenna will be
  presented
• Instructor
• David Kidd, KA7OZO
• Emergency Coordinator (ARES)
• Clackamas Co, Oregon

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Training Points

• What is NVIS?
• How will it work for us?
• How hard is it to use?
• Why should I use it?
• What does it really do for us?
• What materials are needed?

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What is NVIS

• NVIS is a combination of radio hardware, sky wave
  radio propagation, operating procedures,
  cooperation, and knowledge used by a group of
  radio operators who need reliable regional
  communications.
• NVIS fills the gap between line-of-sight ground
  wave and long-distance "skip" sky wave
  communications.

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What is NVIS

• German ground forces first documented NVIS
  techniques in WW-II
• NVIS was more fully documented, studied, and used
  by US forces in Vietnam
• NVIS is still used by todays military in combat
  operations

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What is NVIS

• NVIS propagation is generally considered to be
  F-layer ionospheric reflection at angles of 70-90
  degrees

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How will it work for us?

• Emergency groups such as ARES and RACES are
  studying NVIS propagation, techniques, and
  equipment deployment for emergency preparedness.
• NVIS is the tactical communication system of
  choice in mountainous areas, any areas without
  complete repeater coverage, and all situations
  where repeater-based systems have failed or might
  fail.

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How will it work for us? (Cont)

• With the recent release of manufactured mobile
  and even portable HF radios, HF, and antennas
  employing NVIS propagation, it should become much
  more popular and useful for disaster tactical
  communications.

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What can NVIS do?

• This is a mode of HF radio equipment deployment
  that allows for reliable communications within a
  range of 0-400 miles, and depending on condition
  even farther out.
• NVIS can be viewed more as a "Systems Concept"
  and not just what antenna to use.
• The concept of NVIS is to have reliable
  communications anywhere within an 800 mile
  diameter circle. Your station would be located
  at the center of this circle.

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How hard is it to use?

• NVIS is not just an antenna type or a propagation
  mode -- it is a tactical communications system
  that was designed by military radio operators in
  the field.
• The NVIS antenna is only part of that system. The
  other part is the knowledge and cooperation of
  the operators, which must be accurately applied
  to achieve the best results -- particularly when
  used in life-and-death situations.
• Training and coordination is a key factor in
  making it all work properly.

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How hard is it to use?(Cont)

• Emergency communications should be driven by
  clearly written procedures that have been
  well-designed and tested.
• The procedures should be drilled on a regular
  schedule. The drills should be followed by
  debriefings attended by everyone, so that all can
  learn to avoid future mistakes.
• Suitable procedures are available in books, Field
  Manuals, and on the web. Look for ARES and RACES
  web sites and capture their procedural documents.
  Other excellent sources are FEMA and MARS sites.

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Why should I use it?

• To talk close in under 200 miles
• To have good overall state coverage
• To have multiple frequency capabilities
• To have a system that will work under poor band
  conditions

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Main Reason To Use It

• First and foremost, to completely eliminate the
  skip zone. This enhances all forms of local and
  regional HF communications, for all practical and
  experimental purposes.
• Most of all it can be used effectively for
  emergency operations within a local geographic
  area.

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Among the many advantages of NVIS

• NVIS covers the area which is normally in the
  skip zone, that is, the area normally too far
  away to receive ground-wave signals, but not yet
  far enough away to receive sky-waves reflected
  from the ionosphere.
• NVIS requires no infrastructure such as repeaters
  or satellites. Two stations employing NVIS
  techniques can establish reliable communications
  without the support of any third party.
• Pure NVIS propagation is relatively free from
  fading.

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More Advantages

• Antennas optimized for NVIS are usually low.
  Simple dipoles work very well. A good NVIS
  antenna can be erected easily, in a short amount
  of time, by a small team (or just one person).
• Low areas and valleys are no problem for NVIS
  propagation.
• The path to and from the ionosphere is short and
  direct, resulting in lower path losses due to
  factors such as absorption by the D layer.

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Still More Advantages

• NVIS techniques can dramatically reduce noise and
  interference, resulting in an improved
  signal/noise ratio.
• With its improved signal/noise ratio and low path
  loss, NVIS works well with low power.

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Disadvantages of NVIS operation

• For best results, both stations should be
  optimized for NVIS operation.
• If one station's antenna emphasizes ground-wave
  propagation, while another's emphasizes NVIS
  propagation, the results may be poor.
• Some stations do have antennas which are good for
  NVIS (such as relatively low dipoles) but many do
  not.

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A Few More Disadvantages

• NVIS doesn't work on all HF frequencies.
• Care must be exercised to pick an appropriate
  frequency.
• The frequencies which are best for NVIS are those
  where atmospheric noise is a problem, antenna
  lengths are long, and bandwidths are relatively
  small for digital transmissions.
• Due to differences between daytime and nighttime
  propagation, a minimum of two different
  frequencies must be used to ensure reliable
  around-the-clock communications.

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What materials are needed?

• Materials are dependent on which antenna type you
  want to use
• Dipole fixed or portable position
• Ham stick rotating dipole
• Military type 2- band version
• We will discuss material required for each type
• All are simple to make and use

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N6VNGs NVIS Antenna
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Parts List N6VNGs NVIS

• 2 ea. 1.5" PVC pipes 7.5' long
• 1 ea. 1.5" PVC coupling
• 1 ea. 1.5" PVC cap
• 4 ea. Egg type insulators
• 5 ea. Brass Screws, nuts and washers to fit
  coaxial fitting
• 1 ea. SO-239 or UG-266 female panel-mount
  connector with solder pot center pin
• 5 ea. Stakes (One at the mast center)
• 4 ea. Heavy solder lugs to fit brass screws
• 150' Antenna wire
• 60' Nylon rope
• Coax to rig. As much as you need. Run it up the
  center of the PVC pipe mast and connect to the
  panel-mount

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Construction Notes N6VNGs NVIS

• Drill PVC cap to accept SO-239 and 4 screws and
  nuts
• Mount SO-239 to PVC Cap with screw heads down
• Cut off the head of a brass screw
• Solder a brass screw to center post of SO-239
• Cut antenna wires to length plus a little
• Fit one end of each wire with solder lugs
• Fit the other with the egg insulators
• Install wires to SO-239 using brass nuts and
  washers
• as shown in the figure
• Erect antenna (2 men 5 minutes)
• Tune antenna match for minimum VSWR
• (also could adjust mast height and wire lengths)

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Dual "Ham Stick" version

• Configuration that shows promise for ARES/RACES
  is to take two mono-band mobile antennas and
  mount them base to base, with one being the
  driven. element and the other being the ground
  side.
• Care must be exercised in tuning this
  configuration that the elements are the same
  length.
• They are light weight, portable, fairly
  inexpensive, and easy to put up.

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Dual "Ham Stick" version

• This antenna is available at HRO.
• Antennas are Ironhorse IHF80's and IHF40's (two
  each) and the Ironhorse IH-DAK-AD adapter
• Total cost for four antennas and the mounting
  bracket is 123.75 (as of 2/21/06).
• You can use a Radio Shack tripod and five foot
  mast sections for simplicity or 4 sections of
  cammo poles.
• Plus a run of coax

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40m Rotating Dipole

• KC7TOFs rotating 40m dipole and masting
  configuration
• Very easy to set up and get on the air

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Frequency Possibilities Modes

• 40 meters during the day
• 80 meters at night
• 160 meters at night if 80m is out
• The new 60m band with its power antenna
  limitations can be very effective using NVIS
  techniques.
• Desired modes SSB, RTTY and PACTOR

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Multi-Band NVIS

• 40m, 80m, 160m
• 170 14 stranded wire _at_ 30 with a tuner
• Budwig Hye-Que type connector - 7.95 _at_ HRO
• Insulators - one pair _at_ 1.95
• UV resistant rope for support as needed for
  antenna site

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Real Life NVIS Use

• Fixed dipoles at appropriate height
• Rotating portable dipoles using Ham Sticks
• Military styled X version with 2 band
  capability - portable/fixed position

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In Reality . . .

• Groups of operators using NVIS must understand
  and cooperate on the basics.
• All must be using NVIS antennas (defined as any
  horizontal antenna well under a quarter-wave
  high), as well as the radio hardware and
  propagation theory.
• All must understand that the frequencies used
  must stay between the total absorption and
  vertical MUF ranges.
• The group must decide whether it will equip
  itself to use 160.
• Calling frequencies and other procedures should
  be established, in writing, with contingencies
  clearly stated.

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Actual Field Operation Test

• SET - 9/25/04
• In parking lot adjacent to new county office
  building on Kaen Rd.
• KC7CJOs military version antenna on loan to
  CARES
• Worked great!

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What This Means

• NVIS works
• It is simple to make and simple to use
• NVIS will fill the gaps during poor propagation
  and conditions
• Minimum NVIS capability will cover the entire
  state of Oregon
• NVIS can reach the capitals of the adjoining
  states of CA, NV, WA, ID from our county

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Next Steps

• Since you now know the basics of NVIS, it is time
  to put your knowledge to use
• You can make one, buy one, or borrow one . . .
  Just try it and I know you will become a believer

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Links to NVIS URLs

• www.qsl.net/wb5ude/nvis/
• www.athensarc.org/nvis.htm
• www.w0ipl.com/ECom/NVIS/nvis.htm
• www.co.missoula.mt.us/acs/ACS/NVISpage1.htm
• www.co.missoula.mt.us/acs/ACS/N6VNG20AS2259.htm

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Presentation Credits

• Whats the deal about NVIS? By Dean Straw,
  N6BV, QST Dec 2005
• NVIS Operations by Ed Farmer, AA6ZM, QST, Jan
  1995
• The NVIS - A Low Antenna for Regional
  Communications by Albert Pion, KK7XO, QST, Jun
  2002
• NVIS by Norm Fusaro, W3IC, internet PPP
• Understanding NVIS Antennas Propagation by
  Harold Melton, KV5R, 2002, 2006

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Just about the end

• Questions ?
• Thank you showing interest in NVIS antennas!
• I look forward to helping you get started with
  your NVIS antenna project