Papers and presentations, and more

VOACAP-related papers

Using Propagation Predictions for HF DXing, [2010] Visalia 2010 presentation by Dean Straw, N6BV.
83 pages. 2 MB. Dean N6BV presents his new prediction tables. The newest versions cover 240+ transmitting QTHs around the world. There are two different sets of tables: Summary (each page shows five contest bands for 24 hours to seven general areas around the world), and Detailed (each page shows one band over 24 hours, for 40 zones all around the world).

Contest Antennas. DX or Domestic, What's Your Pleasure?, [2009] Visalia 2009 presentation by Dean Straw, N6BV.
65 pages. 1.5 MB. Topics: Scientifically Planning a Station. There are three elements needed to plan an HF station scientifically: a) The range of elevation angles needed. b) Antenna performance parameters (modeling), and c) The effects of local terrain.

In Search of the Ultima Thule: Can VOACAP Help Find the Ultimate QTH, [2006] by Jari Perkiömäki & George Lane.
58 pages. 20 MB. A story of finding the ultimate QTH to run the CQ WW DX Contest from 160M to 10M during the sunspot minimum (November 2006). We will use VOACAP to tackle the problem from 40M up.

What's the Deal About "NVIS"? [2005] article courtesy by Dean Straw, N6BV.
6 pages. 10 MB. N6BV applies some modern tools to evaluate the Near Vertical Incidence Skywave operating mode — or is NVIS actually an operating strategy?

Another Way to View Propagation Predictions for DXing and Contesting, [2006] Visalia 2006 presentation by Dean Straw, N6BV.
90 pages. 2.4 MB. Topics: Area-coverage predictions using VOAAREA. Graphical comparison of VOAAREA predictions on various amateur radio bands to actual results for the 2005 Sweepstakes Phone contest. How to make customized antennas for VOAAREA.

Improved Guidelines for Automatic Link Establishment Operations, [2005] by George Lane.
10 pages. 680 kB. Frequency scan lists for an ALE link should be populated with frequencies that follow the diurnal MUF variation for the path-month/season. In addition there should be a frequency assigned which approximates the highest of the hourly HPF values and one which falls slightly below the lowest of the hourly FOT values. At this time the FOT-MUF-HPF diurnal values should be those provided by VOACAP with CCIR 1966 Coef. and a minimum angle set to 0.1 degrees. Graphs for the paper [2005].

Review of the High Frequency Ionospheric Communications Enhanced Profile Analysis & Circuit (ICEPAC) Prediction Program, [2005] by George Lane.
10 pages. 300 kB. ICEPAC represents a substantial step toward a more comprehensive HF system performance prediction program and it is now documented. However, the program still seems to be in the development stage with some significant errors. It is recommended that ICECAP be used with caution. It would be well worth the effort to run both VOACAP and ICEPAC. VOACAP should be quite accurate for undisturbed conditions. If ICEPAC deviates greatly from VOACAP output, the predictions should be considered suspect.

Strategies Using Propagation Predictions for DXing and Contesting, [2005] by Dean Straw, N6BV.
64 pages. 1 MB. Why predict propagation? Planning ahead to get that all-time new one. Planning to move a station to other bands where you need him. Planning to be a new one yourself--going on a DXpedition.

How Does VOACAP Compare With These Measurements, [2002?] by Dean Straw, N6BV.
2 pages. 4 MB. The VOACAP ionospheric analysis program has been around in one form or another for three solar cycles. How does its predictions compare to what the Dutch hams measured for mid-November 2001?

Required Signal-to-Interference Ratios for Shortwave Broadcasting, [1997] by George Lane.
8 pages. 7.2 MB. In this paper, several significant experiments are reviewed for the purpose of normalizing their findings to a common set of parameters. The parameters relate to articulation scoring, type of noise, fading of wanted and unwanted signals, type of interference, listener skill, bandwidth of the receiver, carrier frequency offset, etc. The recommended minimum acceptable RSI (required signal-to-interference ratio) for cochannel interference is 36 dB. The RSI needed for 'no perceptible' interference is 53 dB.

Predicting Signal-to-Interference Probability in the High Frequency Band, [1997] by George Lane and Greg Hand.
3 pages. 60 kB. The method developed for computing the S/I (signal-to-interference) distribution where interference consists of the power summation of RF noise and one unwanted signal is totally consistent with the prediction methodology in the IONCAP-family of prediction programs. Care should be exercised in the use of the S/I computation when the wanted and unwanted signals traverse the same common volume of the ionosphere, such as occurs on very short paths.

HamCAP tools

HamCAP User's Guide. The HamCAP software by Alex VE3NEA is a compact freeware interface program to VOACAP, incorporating both graphical Point-to-Point and Area Coverage predictions.

HamCAP Type 13 & 14 Antenna Guide. HamCAP is designed to work with antenna model types 13 and 14 that are just tabulated antenna patterns, 2-D and 1-D respectively, vs. frequency. The program may work with other file types as well, but you will not be able to view the antenna patterns. Learn how to create your own antennas of types 13 and 14.

HamCAP Maps Script. Generate a table as a web page of VOACAP area coverage maps, created by HamCAP.

HamCAP 1.5 User's Guide [PDF, 49 kB]. This is a Japanese translation of the HamCAP User's Guide.

Miscellaneous articles


The Woody Woodpecker Story, Part 3 [PDF, 115 kB] by V. K. Lehtoranta, OH2LX.
This article describes the over-the-horizon radar (OTHR, aka Woodpecker) which operated near Chernobyl during the years 1976-1986, using the pulse frequency of 10 Hz.

Jamming, or deliberate interference against radio broadcasting stations [PDF, 140 kB] by V. K. Lehtoranta, OH2LX.
This article discusses jamming of radio transmissions that were targeted to ordinary people. At one point of time, over 99 % of jamming originated from the areas of the ex-Soviet Union's sphere of influence.


Kokeiluja Faroksella - automaattinen kelimajakoiden kuuluvuudenmittaus vs. keliennusteet. Käytännön kokeiluja VE3NEA:n Faros-nimisellä automaattisella NCDXF:n kelimajakoiden kuuluvuuden mittausohjelmalla ( Faros pystyy ohjaamaan transceiveriä ja tallentamaan kelimajakoista saatavan kuuluvuusdatan kovalevylle. Tämän kokeilun nimenomaisena tarkoituksena oli ja on yhä tarkastella, miten mittaukset tukevat VOACAP:lla tehtäviä statistisia keliennusteita.

Tee täsmäennuste YLE Radio Finlandin lähetyksille. YLE Radio Finland lähettää ulkomaille suunnattuja ohjelmia suomeksi, ruotsiksi, venäjäksi ja latinaksi. Varsinkin kun itse on matkoilla, usein tekee mieli tietää, millä taajuuksilla lähetys kuuluu parhaiten siinä kaupungissa tai lomakohteessa missä sattuukin olemaan.

VOACAP ennustaa kuuluvuuden signaali-kohinasuhteen avulla. VOACAP (Voice of America Coverage Analysis Program) ennustaa HF-alueen (3-30 MHz) radioaaltojen etenemistä tilastollisten todennäköisyyksien pohjalta.

VOACAP taajuussuunnittelun työkaluna. Paneudumme syvemmälle taajuussuunnittelun saloihin tekstimuotoisen ennusteen avulla.

Avaruussään vaikutuksesta HF-keliin. Auringon magneettikentän rakenteen vaihteluista johtuvat aktiivisuusilmiöt aiheuttavat maapallon ionosfäärissä monenlaisia muutoksia. Ionosfääri on Maan ylemmän ilmakehän alue, joka koostuu useammasta sähköisesti varautuneesta eli ionisoituneesta kerroksesta. Auringon UV-säteilyn synnyttämä sähköinen varautuminen on edellytys HF-signaalin taipumiselle.

Avaruussään tarkkailua IonoProbella. IonoProbe on kanadalaisen radioamatöörin Alex Shovkoplyaksen VE3NEA tekemä PC-ohjelma Auringon toiminnan ja Maan magneettikentän tarkkailuun. Ohjelma tarkkailee Internet-lähteitä hyväksikäyttäen HF-etenemisen kannalta oleellisia avaruussääilmiöitä. Ohjelman erikoisuus on kerran tunnissa päivittyvä ionosfääri-indeksi.

Perseus-SDR-vastaanottimen käyttöohje. Perseus on ohjelmistoradio (SDR, software-defined radio), joka toimii erittäin pitkillä, pitkillä, keskipitkillä ja lyhyillä aalloilla (10 kHz - 30 MHz). Tämä tietokoneella käytettävä liikennevastaanotin perustuu erinomaiseen signaalin näytteistykseen suoraan RF-taajuudella (direct sampling), ja sillä on mahdollista tallentaa jopa 1600 kHz:n levyistä taajuusaluetta.


VOACAP förutspår hörbarheten med hjälp av signal-noiseförhållandet. VOACAP (Voice of America Coverage Analysis Program) förutspår radiovågornas framskridande på HF-området (3-30 MHz) genom statistisk sannolikhet.

NTIA/ITS HF software Help Topics

General information on the NTIA/ITS HF Propagation Analysis Package. The development of this set of HF propagation analysis programs was made possible by funding from the Voice of America (VOA), the U.S. Army, and the U.S. Air Force. Anyone interested in continued development is encouraged to do so at any level of funding.

VOACAP. General information - Point-to-Point - Area Coverage - Signal-to-Interference.
The Voice of America Coverage Analysis Program (VOACAP) predicts the expected performance of high frequency (HF) broadcast systems, and in doing so is useful in the planning and operation of HF transmissions for the four seasons, different sunspot activities, hours of the day, and geographic location. VOACAP Frequently Asked Questions (22-Feb-96 Version)

ICEPAC. General information - Point-to-Point - Area Coverage - Signal-to-Interference.
The Ionospheric Communications Enhanced Profile Analysis and Circuit Prediction Program (ICEPAC) predicts the expected performance of high frequency (HF) broadcast systems, and in doing so is useful in the planning and operation of HF transmissions for the four seasons, different sunspot activities, hours of the day, and geographic location.

REC533. General information - Point-to-Point - Area Coverage.
REC533 (ITU-RS Recommendation 533) is a PC/Windows based implementation of the International Telecommunication Union's (ITU) propagation model Recommendation ITU-R PI.533. It predicts the expected performance of high frequency(HF) broadcast systems, and in doing so is useful in the planning and operation of HF transmissions for the four seasons, different sunspot activities, hours of the day, and geographic location. 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. This information was extracted from an ancient informal letter from Ray Rosich dated June 8, 1978. It has been included here as an item of historical significance. Remember, any reference to 'latest' means as of June 1978.

Introduction to the ICEPAC Technical Description. Technical Description of ICEPAC Propagation Prediction Program. by Frank G. Stewart. Simulation models have been developed for predicting and analyzing the performance of HF systems that depend on ionospheric propagation. These models are documented.

Excerpts from Original ICEPAC User's Manual. This report describes the operation and use of the Ionospheric Communications Enhanced Profile Analysis and Circuit Prediction Program (ICEPAC). The computer program is an integrated system of subroutines designed to predict high-frequency (HF) sky-wave system performance and analyze ionospheric parameters. These computer-aided predictions may be used in the planning and operation of high-frequency communication systems using sky-waves. This report contains instructions for the use of ICEPAC.

Corrections to Man-made Noise. In my (George Lane) last conversation with Don Spaulding before his retirement from Federal Service (March 3rd), he asked if I would publish a correction to his report.

Note on MUFDAYs. MUFDAY is the fraction of the days of the month that the operating frequency will be below the mode MUF. In other words it is the fraction of days one can expect normal ionospheric reflection for the indicated most reliable mode at that frequency.

High Latitude Errors. Computer prediction programs which use the 'expected excess system loss' term may contain an error. The programs suspected of having this error are the original IONCAP, ICEPAC, VOACAP and other IONCAP derived programs. The error is contained in the files used by ITU-R PI. Recommendation 533 but at present that prediction program does not call the parameter which is in error. ITSA-1 may contain the error. It does not seem that ITS-78 or HFMUFES has the error since these programs have different values for excess system loss. VOACAP users should download VOACAP 94.1114 or any subsequent version.

Corrected Signal-to-Noise Ratio Distribution. The correction to the SNR distribution in VOACAP results in a change in the RPWRG of more than 1 dB in 25 to 40% of the usable frequency-hours for paths of more than 3000 km. More differences are found in high sunspot years than low. Also more differences occur for low latitudes than high latitudes. The most significant changes occur for frequencies of less than 10 MHz on circuits with path lengths of less than 3,000 km.

A Comparison of Broadcast Quality to VOACAP using Methods 21, 22, and 30. VOACAP predictions and coverage maps run with REL set at 0.90 provide a good estimate of signal quality 90% of the time. Employing the smoothing algorithm (Method 30) for circuit distances greater than 7,000 km is preferable to using Method 20 or 22 (ray hop) alone.

VOACAP Method 30. A Long Path/Short Path Smoothing Function. The VOACAP prediction is more accurate at the lower decile of the signal power distribution than at the median value. This is true because the signal power distributions are often non-Gaussian and/or bimodal. The lower decile value is based on actual measurements and not on an assumed distribution function. Consequently, the smoothing function is applied to the lower decile of the signal power distribution.