by Jari Perkiömäki, OH6BG/OG6G
VOACAP Quick GuideHF Propagation Prediction and Ionospheric Communications Analysis
What is VOACAP?
VOACAP (Voice of America Coverage Analysis Program) is free professional high-frequency (HF) propagation prediction software from NTIA/ITS, originally developed for Voice of America (VOA).
This 'work-in-progress' guide should get you well started with the software. A more comprehensive discussion about the finer details of using the software can be found in George Lane's book Signal-to-Noise Predictions Using VOACAP. A User's Guide. The book is now available on CD-ROM.
There is now also "The Official VOACAP Blog" - well, it's not too official.
NOTE: Running automated scripts to access VOACAP services is strictly prohibited unless agreed upon in advance with the VOACAP site owners.
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Real Propagation Visualized with FT8 Data
Explore the 50,000+ real-life propagation charts from one ITU zone to another ITU zone over the months of 2017-2019!
VOACAP Online Prediction Services
Point-to-Point Predictions Coverage Area Maps VOACAP Propagation Planner
Visual tool for HF contesters and DXers
VOACAP DX charts
Predictions for upcoming DXpeditions
Other VOACAP Related Services
- Current International Smoothed Sunspot Numbers, Ri, to be used in VOACAP, from SIDC
- Current Space Weather: Solar Wind, Magnetogram, X-Rays, Protons
- QTH Locator - find coordinates and Maidenhead locators on Google Maps
- How to Run VOACAP under Apple Macintosh OS X? - a quick guide to making text-based VOACAP predictions
- Elevation-Angle Analyzer - generate statistical elevation-angle data for HFTA
- Statistical elevation-angle distribution - a case study
- Graphical User Interface for VOACAP for Linux
- Rockwell Collins offers VOACAP User's Guide on CD-ROM for free (shipping charges apply)
- World Radio Broadcasting Stations - explore various BC transmitting sites on Google Maps
- My blog in Finnish: VOACAP, ennusteet ja antennit
- Sunrise and sunset times around the world
- Today's Sunrise and Sunset Times by DXCC country
1. Downloading VOACAP
- Download from Greg Hand's site, all new updates of the ITSHFBC package are available here
- Alternative direct download, 8 Dec 2009 version (3.1 MB)
- Download the Fortran source codes of the VOACAP Propagation Prediction Engine, in a special directory as ZIP files.
- VOACAP for Linux by J.A.Watson (M0DNS), an exciting project to make VOACAP available for Linux users. Please contribute!
- Release 3 is out! Download the new VOACAP Linux GUI, Release 3! (1.5 MB gzipped file). Now supports Area Coverage Maps with Jim Watson's VoaAreaPlot! This software is supplied 'as is' without any warranty, implied or otherwise. right-click and save the target. All users of Release 1 are strongly encouraged to upgrade, due to the bugs in R1.
- VOACAP for Linux Software
2. VOACAP - Backgrounds & Running the Prediction
- VOACAP Overview
- Screenshots of VOACAP
- Modelling the real-life HF communication system into VOACAP
- Setting VOACAP input parameters
- Textual circuit prediction (Run > Circuit)
- Graphical circuit prediction (Run > Graph)
- Area coverage prediction (VOAAREA)
The calculation engine, VOACAPW
Graphs & Colours
- VOACAP & VOAAREA contours
- VOACAP & VOAAREA plot colors
- Y-axis scaling for VOACAP Time & Distance graphs
3. VOACAP - Understanding the Prediction
- Ten Common Mistakes in Using VOACAP
- Field Strength vs. Signal-to-Noise
- Choosing the correct Sunspot Number
- VOACAP Predictions at Low Frequencies
- Comparing VOACAP, ICEPAC and REC533
- Method 25: Ionospheric Parameters and Semi-thickness
MUF, SNR and REL
- The MUF and SNR Distribution: Choosing the Best Frequency
- Understanding Above-the-MUF Predictions
- Calculating the MUFdays
- Maintaining the Required Grade of Service: Calculating the Circuit Reliability for a Given Hour
Signal Power & Noise Power
Antennas & Radiation Angles
- Method 15, or Transmitter & Receiver AntennaPatterns
- VOACAP Angle Predictions
- Minimum Angle in VOACAP
- Predicting the Takeoff Angle Parameter TANGLE
4. VOACAP - Case Studies
5. VOACAP-related Papers
- Using Propagation Predictions for HF DXing  Visalia 2010 presentation by Dean Straw, N6BV.
- Contest Antennas. DX or Domestic, What’s Your Pleasure?  Visalia 2009 presentation by Dean Straw, N6BV.
- What’s the Deal About “NVIS”?,  article courtesy by Dean Straw, N6BV
- Another Way to View Propagation Predictions for DXing and Contesting  Visalia 2006 presentation by Dean Straw, N6BV.
- In Search of the Ultima Thule. Can VOACAP Help Find the Ultimate QTH?  CCF/OHDXF presentation by Jari Perkiömäki & George Lane.
- Improved Guidelines for Automatic Link Establishment Operations  by George Lane
- Graphs for the paper 
- Review of the High Frequency Ionospheric Communications Enhanced Profile Analysis & Circuit (ICEPAC) Prediction Program  by George Lane
- Required Signal-to-Interference Ratios for Shortwave Broadcasting, [7.2 MB] by George Lane, 1997
- Predicting Signal-to-Interference Probability in the High Frequency Band, [60 kB] by George Lane and Greg Hand, 1997
- Strategies Using Propagation Predictions for DXing and Contesting, by Dean Straw, N6BV
- What is VOACAP Trying to Tell Me? by Dean Straw, N6BV
- How Does VOACAP Compare With These Measurements, by Dean Straw, N6BV
6. NTIA/ITS HF software HELP Topics
- General information on the NTIA/ITS HF Propagation Analysis Package
- VOACAP. General information - Point-to-Point - Area Coverage - Signal-to-Interference.
Voice of America Coverage Analysis Program
- VOACAP Frequently Asked Questions (22-Feb-96 Version)
- ICEPAC. General information - Point-to-Point - Area Coverage - Signal-to-Interference.
Ionospheric Communications Enhanced Profile Analysis and Circuit Prediction Program
- REC533. General information - Point-to-Point - Area Coverage.
ITU-RS Recommendation 533. This has been updated to the ITU 1996 Version 3.
- Data Files Frequently Asked Questions
- Helpful documents on using the propagation models
- History (Part 1) of HF propagation models by Ray Rosich, 1978
- Introduction to the ICEPAC Technical Description
- Excerpts from Original ICEPAC User's Manual
- Corrections to Man-made Noise
- Note on MUFDAYs
- High Latitude Errors
- Corrected Signal-to-Noise Ratio Distribution
- A Comparison of Broadcast Quality to VOACAP using Methods 21, 22, and 30
- VOACAP Method 30. A Long Path/Short Path Smoothing Function
7. HamCAP User's Guide
8. Articles of interest
- The Woody Woodpecker Story, Part 3 [PDF, 115 kB] by V. K. Lehtoranta, OH2LX
- Jamming, or deliberate interference against radio broadcasting stations [PDF, 140 kB] by V. K. Lehtoranta, OH2LX
- www.radiojamming.info by Rimantas Pleikys
- Kokeiluja Faroksella - automaattinen kelimajakoiden kuuluvuudenmittaus vs. keliennusteet
- Tee-se-itse täsmäennuste YLE Radio Finlandin lähetyksille
- VOACAP ennustaa kuuluvuuden signaali-kohinasuhteen avulla
- VOACAP taajuussuunnittelun työkaluna
- Avaruussään vaikutuksesta HF-keliin
- Avaruussään tarkkailua IonoProbella
- HamCAP 1.5 User's Guide [PDF, 49 kB]
9. Tools & downloadable files for use with VOACAPFind coordinates and Maidenhead grid locators just by pointing and clicking
- Browse the World with Google Maps, (start view: World)
- Browse the World with Google Maps, (start view: Scandinavia)
- World Radio Broadcasting Stations on Google Maps! new
- QTH Locator (Google Maps), updated!
- MAKEVOA.EXE for creating VOACAP-compatible antenna models from HFTA, courtesy of R. Dean Straw N6BV (zipped, 34 kB)
- Elevation-Angle Analyzer for VOACAP, v1.0
- Windows program (zipped, 830 kB) for conversion of on-line CTY.DAT to CTY.GEO [9 Dec 07]. Mac and Linux versions available upon request!
- Perl source code for conversion of WL_CTY.DAT to CTY.GEO
Coordinate filesSave the coordinate files (*.GEO) at C:\ITSHFBC\GEOCITY\
- New country coordinate list from CTY.DAT by AD1C. [9 Dec 07]
- GEO file for all Zones (WAZ). Courtesy of Peter Ackermann DL3NAA.
- Latest Global HF Transmitter Site List. [5 Aug 06]
- Latest country coordinate list by OH6BG. [30 Jul 06]
- Latest NCDXF beacon coordinate list [30 Jul 06]
- Finland city coordinate list
Antenna and configuration files
- A collection of antennas for use with VOACAP is available. If you wish to contribute, please let me know.
- Fine-tuned VOACAP Point-to-Point parameter auto scaling settings, English. Save as C:\ITSHFBC\DATABASE\Voacap.gph
- Fine-tuned VOACAP Point-to-Point parameter auto scaling settings, Finnish. Tallenna nimellä C:\ITSHFBC\DATABASE\Voacap.gph
- Fine-tuned Y-axis scaling for VOACAP Time & Distance graphs. Save as C:\ITSHFBC\DATABASE\voadist.gph
- Fine-tuned colors for auto-contour shading for Point-to-Point plots. Save as C:\ITSHFBC\DATABASE\Colors.gph
- 4NEC2, a free NEC-based antenna modeler and optimizer by Arie Voors, can export antenna models to VOACAP antenna format
Special ThanksI wish to thank Mr George Lane for his friendship, invaluable comments and guidance - and his patience in this project. A special thank-you to Greg Hand who still maintains the code.
Disclaimer: Any software or service on this website is provided "as is". Use at your own risk.
© 2003-2020 Jari Perkiömäki OH6BG/OG6G. SSN source for all VOACAP Online services: WDC-SILSO, Royal Observatory of Belgium, Brussels. Last update: 2 January 2020.