Transcript PROPAGATION OF ELECTRO

HOW DOES MY SIGNAL
GET FROM HERE TO THERE?
By Forest Cummings, W5LQU
And Dave Russell, W2DMR
THE ELECTROMAGNETIC WAVE
GENERATION OF AN EM WAVE
Current flow
E field
H field
Antenna
DISTANCE SQUARED
MODES OF TRANSMISSION
Line of sight
Ground Wave – low frequencies
Reflections – most important for HF
Special Cases – scatter, ducting
IONOSPHERIC LAYERS
Are created by the UV and X-ray
radiation from the sun.
The D layer (50mi) is an absorption
layer affecting frequencies from 1.8
MHz to 7 MHz.
The E layer (70mi) is a sporadic layer
with some very interesting effects.
The F layers are the most Important for
HF bands long range communication.
IONOSPHERE
ELECTRON DENSITIES
Variations in the ionosphere electron
densities occur for several reasons:
Day and night
Summer and Winter
The 11 year solar sunspot cycle
Solar storms
IONOSPHERIC REFRACTION
IONOSHERIC SKIP ZONES
MAXIMUM USEABLE FREQ
The maximum useable frequency is the highest
frequency that can be refracted by the ionospheric
layer
This is commonly called the
MUF
Frequencies higher than the MUF will penetrate the
Ionosphere and will escape into space
It is best to choose a frequency just below the MUF
PROPAGATION CHART
Propagation Charts are made
for certain paths and specific
dates and time periods.
They show the variations of
the MUF during a 24 hour period
AZIMUTHAL MAP
If you have a directional antenna it
is not intuitive to really know exactly
which direction to point it to reach the
desired target area.
This Azimuthal Map shows directions
to the world from Dallas, Texas.
SUNSPOT CYCLES
This chart is from the January 2005 QST
Maunder minimum
AD 1645 - 1715
SUNSPOT CYCLE 23
GEOMAGNETIC ACTIVITY
TROPOSPHERIC SCATTER
DUCTING
PROPOGATION CHART
RECEIVER NOISE
The last link in the communications path is the receiver and
conditions at the receiver location. Noise at the receive site
is the primary limitation.
+40 dB
20 dB/octave
Man
290 K
Thermal
Made
10 MHz
20 dB/decade
Galactic
20 MHz
NOISE LEVELS VS FREQUENCY
200 MHz
MF (300Hz – 3MHz)
160 meters (1.8 – 2.0 MHz)
High D layer absorption
Good ground wave coverage – up to 90 miles
High manmade and atmospheric noise
Worldwide night time coverage – F2 layer
HF (3 – 30 MHz)
80 meters (3.5 – 4.0 MHz)
Similar to 160m
D layer absorption not quite as bad as 160m
Some E layer skip in the daytime
High manmade and atmospheric noise
Pretty good ground wave coverage – 40 miles
Worldwide night time coverage – F2 layer
HF (3 – 30 MHz) 1
40 Meters (7.0 – 7.3 MHz)
Mild D layer absorption
Noise levels lower
Defined daytime skip zone
Short skip on E and F layers
Worldwide night time coverage even at Solar minimum – F2 layer
30 meters (10.1 – 10.15 MHz) CW only
D layer not significant
Generally open 24 hours for F2 layer coverage
Good throughout the Solar cycle
HF (3 – 30 MHZ) 2
20 meters (14.0 – 14.35MHz)
Primary long haul DX band
F2 layer propagation during the day
May stay open all night at Solar maximum
Low atmospheric noise and some E layer short skip
Most popular but crowded Band
17 meters (18.068 – 18.168 MHz)
Very similar to 20 meters
Solar effects more pronounced
Mostly daytime and early evening
Not usually as crowded as 20 meters
HF (3 – 30 MHZ) 3
15 meters (21.0 – 21.45 MHz)
Primary DX band at Solar maximum
Sensitive to changing Solar activity
Basically daytime, but early night at Solar maximum
Only some sporadic E at Solar minimum
12 meters (24.89 – 24.99 MHz)
Open only during moderate to high Solar activity
Some sporadic E in late spring and summer
HF (3 – 30 MHZ) 4 / VHF
10 meters (28.0 – 29.6 MHz)
Extreme variations in propagation modes
Very efficient F2 propagation at Solar maximum with low power
Single and multiple hop propagation
Open sunrise to few hours past sunset
No propagation at Solar minimum except sporadic E, aurora, meteor scatter
6 meters (50.0 – 54.0 MHz) “The Magic Band” really VHF (30 – 300MHz)
World wide daylight DX at Solar maximum
Sporadic E is most common and popular mode
Regular tropospheric scatter
Auroral propagation in afternoons when Solar magnetic activity
Ducting is rare
VHF (30 – 300MHZ)
2 meters (144 – 148 MHz)
No F propagation
Line of sight dependent on antenna height
Some sporadic E similar to 6 meters
Tropospheric scatter and ducting up to 500 miles
Auroral and meteor scatter
135 cm (222 – 225 MHz)
Nearly as good as 2 meters
Sporadic E is rare
UHF (300 3000 MHZ)
70 cm (420 – 450 MHz)
Line of sight dependent on height of antennas
No sporadic E, but some Auroral scatter
Tropospheric scatter and ducting is good
33 cm (902 – 928 MHz) and higher
No ionospheric modes of propagation
Line of sight dependent on height of antenna
High gain antennas
Auroral and Tropospheric scatter
Very sensitive to changes in weather
IN CONCLUSION
LISTEN A LOT
Get acquainted with the bands, and the variation in propagation conditions
due to weather, day/night, seasonal, and Solar activity. But, above all;
ENJOY HAM RADIO
AND
HAVE FUN !