Central Idaho Amateur
Radio Club
     
CIARC - Current Propagation
About This Propagation Page

This page will self-refresh every 15 minutes. Clicking on a graph, map or chart will open the web page with the original source data. The NVIS World Map data from Australia is updated hourly while the foF2 Critical Frequency Plot from Austin is updated every 15 minutes.


Table of Contents


To learn how to interpret the propagation information on this page, please visit the HF NVIS Frequency Selection page by selecting that page under the Resources menu above, or by clicking here.


Sun Spot Number Progression

IF NO IMAGE IS DISPLAYED THEN SUN SPOT CYCLE DATA IS CURRENTLY UNAVAILABLE

UTC Time

Grey Line Propagation

IF NO IMAGE IS DISPLAYED THEN GREYLINE DATA IS CURRENTLY UNAVAILABLE
Aurora

IF NO IMAGE IS DISPLAYED THEN AURORA DATA IS CURRENTLY UNAVAILABLE
Current Long Range HF Propagation
Solar Weather & Band Conditions

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Maximum Usable Frequency (MUF) Map

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Key For Above Map
RED Contour lines indicate X-Rays reach a level that is capable of producing short wave fade-outs on sun lit paths.
GREEN Green bands indicate radio auroral zones, where radio signals will experience fading, multi-path and absorption.
YELLOW Sun Symbol.
GRAY Regions that indicate where the sun is rising or setting, to 12° below the horizon (i.e. gray-line). Improved propagation is possible due to the loss of ionization in the D-region, while ionization remains longer in the F-region, allowing for longer propagation.

The MUF for any 3,000 kilometer (1,864 mile) path can be determined by finding the midpoint (or half-way point) of the path and examining the MUF at that midpoint on the map by finding the labelled MUF contour value. All contours are given in MHz.

For 4,000 kilometer (2,485 mile) paths, multiply the given contoured MUF values by 1.1. The MUF for the given 4,000 km (2,485 mile) path is then determined at the midpoint of the desired path.

For longer path lengths, divide the path into equal 3,000 km (1,864 mile) or 4,000 km (2,485 mile) segments and compute the MUFs corresponding to the two midpoints that are 1,500 km (932 mile) or 2,000 km (1,242 mile) from each end of the path. Then select the lower of these two MUFs.



For an absolutely fantastic point to point prediction that depicts probabilities for each band and allows for determining the best frequency and best time to make a long distance HF contact, please see VOACAP Online.

The quick guide for VOACAP Online can be found here.

The manual for VOACAP Online can be found here.



To create a coverage prediction map for any given band, use VOACAP based coverage prediction.


Current HF NVIS Propagation
foF2 Critical Frequency Map

THE CRITICAL FREQUENCY MAP DATA FROM AUSTRALIA IS CURRENTLY UNAVAILABLE

D-Layer Absorption Frequency Map

IF NO IMAGE IS DISPLAYED THEN THE NOAA D-REGION PREDICTION IS CURRENTLY UNAVAILABLE

The D-Layer Absorption Frequency, which is indicated by color shading in the map above, represents the lowest frequency that can be used for NVIS or long-hop propagation.


5 MHz D-Layer Absorption Attenuation Map

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10 MHz D-Layer Absorption Attenuation Map

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Polar -10 dB D-Layer Absorption Attenuation Map

IF NO IMAGE IS DISPLAYED THEN THE NOAA D-REGION PREDICTION IS CURRENTLY UNAVAILABLE
Austin Ionosonde

Using NVIS propagation is possible between the foF2 Critical Frequency and the lowest frequency for which the D layer does not excessively attenuate the signal (i.e. the Lowest Usable Frequency or LUF). Signals higher in frequency than the foF2 critical frequency will not be reflected back to Earth and will pass into outer space. Frequencies below the Lowest Usable Frequency (LUF) are attenuated to the point where they are not usable for communications. The LUF increases during periods of high solar activity due to higher levels of ionization in the D-Layer, which results in higher levels of attenuation in this layer. D-layer absorption is characterized by no echoes being received at the low frequency end of the Ionosonde (see Digisonde below).


You are not seeing the Austin digisonde image.  Click on the image icon, or this text, to visit the source page
						where the image resides.  The source page, 
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Note that the critical frequency (CF), which is appropriate for good NVIS communications, is approximately 1/3 of the maximum usable frequency (MUF). The critical frequency (CF) is indicated at the foF2 entry at the top left of the Austin digisonde image immediately above.



Boulder Ionosonde

Boulder Ionosonde Data

Austin foF2 Critical Frequency Trend

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Because of differences in latitude and longitude between Austin and Southwest Idaho, the conditions in Southwest Idaho may not reach as high as an foF2 critical frequency as depicted and will lag the foF2 critical frequency trend recorded at Austin.


National Weather System Alerts
NWS National Alerts

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NWS Alerts - Color Key


 
911 Telephone Outage
 
Administrative Message
 
Air Quality Alert
 
Air Stagnation Advisory
 
Arroyo & Small Strm Flood Advisory
 
Ashfall Advisory
 
Ashfall Warning
 
Avalanche Advisory
 
Avalanche Warning
 
Avalanche Watch
 
Beach Hazards Statement
 
Blizzard Warning
 
Blizzard Watch
 
Blowing Dust
 
Brisk Wind Advisory
 
Child Abduction Emergency
 
Civil Danger Warning
 
Civil Emergency Message
 
Coastal Flood Advisory
 
Costal Flood Statement
 
Costal Flood Warning
 
Coastal Flood Watch
 
Dense Fog Advisory
 
Dense Smoke Advisory
 
Dust Storm Warning
 
Earthquake Warning
 
Evacuation - Immediate
 
Excessive Heat Warning
 
Excessive Heat Watch
 
Excessive Cold Warning
 
Extreme Cold Watch
 
Extreme Fire Danger
 
Extreme Wind Warning
 
Fire Warning
 
Fire Weather Watch
 
Flash Flood Statement
 
Flash Flood Warning
 
Flash Flood Watch
 
Flood Advisory
 
Flood Statement
 
Flood Warning
 
Flood Watch
 
Freezing Warning
 
Freeze Watch
 
Freezing Fog Advisory
 
Freezing Rain Advisory
 
Freezing Spray Advisory
 
Frost Advisory
 
Gale Warning
 
Gale Watch
 
Hard Freeze Warning
 
Hazardous Materials Warning
 
Hazardous Seas Warning
 
Hazardous Seas Watch
 
Hazardous Weather Outlook
 
Heat Advisory
 
Heavy Freezing Spray Warning
 
Heavy Freezing Spray Watch
 
High Surf Advisory
 
High Surf Warning
 
High Wind Warning
 
High Wind Watch
 
Hurricane Force Wind Warning
 
Hurricane Force Wind Watch
 
Hurricane Local Statement
 
Hurricane Warning
 
Hurricane Watch
 
Hydrologic Advisory
 
Hydrologic Outlook
 
Ice Storm Warning
 
Lake Effect Snow Advisory
 
Lake Effect Snow Warning
 
Lake Effect Snow Watch
 
Lake Wind Advisory
 
Lakeshore Flood Advisory
 
Lakeshore Flood Statement
 
Lakeshore Flood Warning
 
Lakeshore Flood Watch
 
Law Enforcement Warning
 
Local Area Emergency
 
Low Water Advisory
 
Marine Weather Statement
 
Nuclear Power Plant Warning
 
Radiological Hazard Warning
 
Red Flag Warning
 
Rip Current Statement
 
Severe Thunderstorm Warning
 
Severe Thunderstorm Watch
 
Severe Weather Statement
 
Shelter In Place Warning
 
Short Term Forecast
 
Sm. Crft. Advisory
 
Sm. Crft. Advisory - Hazardous Seas
 
Sm. Crft. Advisory - Rough Bar
 
Sm. Crft. Advisory for Winds
 
Small Stream Flood Warning
 
Special Marine Warning
 
Special Weather Statement
 
Storm Watch
 
Test
 
Tornado Warning
 
Tornado Watch
 
Tropical Depression Local Statement
 
Tropical Storm Local Statement
 
Tropical Storm Warning
 
Tropical Storm Watch
 
Tsunami Advisory
 
Tsunami Warning
 
Tsunami Watch
 
Typhoon Local Statement
 
Typhoon Warning
 
Typhoon Watch
 
Urban & Small Strm Flood Advisory
 
Volcano Warning
 
Wind Advisory
 
Wind Chill Advisory
 
Wind Chill Warning
 
Wind Chill Watch
 
Winter Storm Warning
 
Winter Storm Watch
 
Winter Weather Advisory