GWEN
And Ground Wave
Propagation
What is Ground Wave?
• It is a mode of propagation generated
only by vertical polarization.
• It is used exclusively by the broadcast
industry for their transmissions.
• Radio waves remain in contact with
the earth.
• VLF range is thousands of miles.
Ground Wave Propagation is:
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Best employed on the 160 and 80M bands.
Ideal for 60 to 100+ mile range.
Great daytime communication, low noise.
Takes advantage of the “D” layer screening.
Range Km= 200/(sqrt(Fmhz)).
Induced currents in the ground cause tilts.
Higher the freq. the more the tilt.
Fresh water is akin to poor soil conditions.
GWEN is immune to high altitude EMP
originating from a nuclear detonation.
Surface or Diffracted Wave
• This is the portion of the wave that is in
contact with the earth.
• It’s losses are determined by the quality of
the soil.
• The wave tilts forward as it moves.
Why Not NVIS?
• Near Vertical Incident Skywave range is
determined by antenna height and ionization
in the upper ionosphere, and is subject to
change from hour to hour ,day to day, and
season to season.
• Ground wave suffers little from these
effects as verified by listening to an AM
radio station within 100 miles of you.
Ground Wave Testing
•Tests were done with a portable vertical antenna
27 feet long with 8 suspended radials two feet off
the ground. Peter VA3WET was the out station.
•Tests were done over the period of one year at
various places throughout Southern Ontario.
•The tests were done at a radius of 100Kms from
the base station in NOTL.
•Power levels were 80W, 40W and 20W or 3dB
down.
NOTL Base Station GWEN
•The base station was running 50 W during all
testing.
•A 46 foot top loaded vertical with 48, 40 foot
ground radials on the surface of the soil.
•An old FT 102 was used for the occasions.
Results of the tests!
•As expected the worst case was at the 20W levels
of power.
•At this level Peter was just above an S5.
•The copy was spotty at times but the “S” meter
remained constant while generating a constant tone
so we knew we were on groundwave.
•If the remote station was replaced by a base
station there would have been a S9 copy.
GWEN and Frequency
• As the frequency increases so do the losses.
• Signals above 40M tend to become useless
for ground wave operation.
• Vertical polarization only can be used for
Ground Wave.
• Horizontally polarized signals are either
absorbed or reflected into the ionosphere.
VHF / UHF
• These frequencies are propagated in line of
sight, therefore have very limited distance.
• Some distance is gained by refraction or
antenna elevation.
• The rule is (sqrt 1.5xAh(in feet)).
• Repeaters become necessary for consistent
signals.
ARES GWEN
• If existing VHF/UHF stations are within simplex
range of each other, we have a limited guaranteed
communication.
• This setup would produce a working link with all
the cells in your area.
• Still there would be no link with the outside world,
that area outside of VHF/UHF range.
• HF ground wave would serve to link other areas of
vhf/uhf interest.
• The range of one HF link is equal to five
VHF/UHF links or roughly 100kms.
ARES SET
• All ARES cells operate on simplex to verify
communications are established.
• Any antenna and power adjustments be changed to
guarantee those communications.
• HF cells operate only on SSB or CW to keep
technology to a minimum.
• PSK31 tests will be performed to see if 160 Km
can be established putting the London area within
range of NOTL.
UP and Running
• When all VHF /UHF links are compliant,
and 100km range established between two
HF ground wave outstations.
• Then you have an emergency
communication system bar none.
An HF Benefit
• Most, but not all HF stations can and do run
high power.
• This can be instrumental in achieving
stronger CW signals and clearer SSB
reception.
Service to the Community
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This is why ARES was formed.
It should try to cover every eventuality.
Use every resource available to it.
Train its people in NTS traffic handling.
Have impromptu SETs.
Become involved with hospitals, shelters.
If Interested!
• Get together with your ARES group and
discuss the possibility of your own HF link.
• The dream would be to encircle all Southern
Ontario with such a link from windsor to
Ottawa.
• Copies of this presentation are available,
• Just e-mail me “ve3bbn@gmail.com”
Ground Wave Emergency Network
Southern Ontario Coverage
Questions?
Thank you for your time