VOACAP Online
User’s Manual

VOACAP: Your edge in the HF spectrum.

Jari Perkiömäki, OH6BG

© 2024 Jari Perkiömäki, OH6BG. All content in this document, including but not limited to text, images, and code, isprotected by copyright and is the exclusive property of the author, Jari Perkiömäki. No portion of this content may
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Any unauthorized use of this content will be considered a violation of copyright law and may result in legal action.
For inquiries regarding permission to use this content, please contact the author.
Last revision: August 1, 2024

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TABLE OF CONTENTSVOACAP Online User’s Manual ........................................................................................................................................... 1
Pinpointing Your Location: The Interactive Map............................................................................................................. 4
Short-Path and Long-Path Visualization ........................................................................................................................ 5
The Data Bar .................................................................................................................................................................. 5
Setting the Date and Grayline Terminator ...................................................................................................................... 6
Your Time Machine: The Pop-Up Calendar ........................................................................................................... 6
The Time Slider ........................................................................................................................................................ 6
Sunrise and Sunset Insights ........................................................................................................................................... 6
Navigating the Input Parameters ................................................................................................................................... 7
Left-Side Controls .................................................................................................................................................... 7
Right-Side Controls ................................................................................................................................................. 8
Settings for Precision Control ....................................................................................................................................... 10
Deep Dive into the Importance of the Minimum Take-off Angle Setting ........................................................ 12Your HF Toolkit: The Deep Dive........................................................................................................................................ 15
1. Prop Charts & Prop Wheel ....................................................................................................................................... 15
Prop Charts .............................................................................................................................................................. 15
Predicting Prime Time for Radio Communication ................................................................................................. 17
Prop Wheel .............................................................................................................................................................. 18
Getting Started with Propagation Prediction Analysis ........................................................................................... 19
2. Band-by-band: The Big Picture ............................................................................................................................... 20
3. REL | SDBW | SNR: Three-in-One Predictions .......................................................................................................... 20
4. Best FREQ: Guide to Optimal Frequency Selection................................................................................................. 21
5. Total: Detailed Propagation Statistics ..................................................................................................................... 22
6. All-Year Propagation Predictions ............................................................................................................................. 24
7. QSO Window: Your Secret Weapon for DX Success ................................................................................................. 26
8. Antenna: Comparative Antenna Performance Analysis .......................................................................................... 27
9. TO Angle: A Journey into Take-Oﬀ Angles ............................................................................................................... 28
10. Propagation Planner: Your Key to Contest and DX Success .................................................................................. 30
11. Planner DIY: Your Personalized Propagation Snapshot ........................................................................................ 32
12. P2P Grayline: Exploring Low-Band Propagation ................................................................................................... 33
13. Exploring the Power of Coverage Area Maps ......................................................................................................... 35
14. DXCC Grayline aka VOACAP Greyline ..................................................................................................................... 36
15. Space WX: Understanding Ionospheric Disturbances ........................................................................................... 37
16. Discover Earth-Moon-Earth (EME) Times .............................................................................................................. 38

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Say hello to intuitive prediction tools! VOACAP Online brings the power of the renowned Voice ofAmerica Coverage Analysis Program (VOACAP) to your fingertips, offering a streamlined
experience for both novice and seasoned HF enthusiasts.
This improved service consolidates the best features of our previous platforms, providing a onestop shop for all your HF propagation needs. Whether you're planning a DXpedition, strategizing
for a contest, or simply curious about current conditions, VOACAP Online empowers you to
explore the fascinating world of HF propagation with ease and precision.

Pinpointing Your Location: The Interactive Map
One of the most powerful features of VOACAP Online is its user-friendly interactive map. Gone
are the days of manually inputting latitude and longitude! Simply drag and drop the red(transmitter) and blue (receiver) markers to your desired locations, and watch as the map
updates in real-time, displaying:Distance and Bearing: Instantly see the distance (in kilometers and miles) and bearing(from True North) for both short-path and long-path great-circle circuits.
Geographical Midpoint: Visualize the midpoint of your chosen path, providing valuable
insights for propagation analysis.
Dynamic Updates: Move the markers freely to explore different propagation paths andinstantly see how distance, bearing, and midpoint change.

VOACAP Online offers unparalleled flexibility for defining your transmitter and receiverlocations. In addition to the interactive map, you can also input coordinates using:

DXCC Country Selection: Choose from a comprehensive list of DXCC entities, withmeticulously researched coordinates for pinpoint accuracy.
Maidenhead Grid Locator: Enter grid squares directly, and the tool will automaticallycalculate and populate the corresponding latitude and longitude.
4Manual Latitude/Longitude Entry: For ultimate precision, manually input your desired
coordinates.

Easily swap the transmit (TX) and receive (RX) locations by double-clicking the blue (RX)marker. This action triggers a recalculation of the propagation prediction and other relevant
details. Notice that circuit predictions are not always perfectly reciprocal after swapping TX andRX locations. This discrepancy in VOACAP calculations primarily stems from variations in noise
power levels at the receive site(s).

Short-Path and Long-Path Visualization
VOACAP Online doesn't just connect two points on a map; it reveals the invisible highways ofradio waves that link them. As you position your transmitter (red) and receiver (blue) markers,
notice the two distinct paths that appear:The Short Path (Green Line): This solid green arc represents the most direct, shortest
distance between your transmitter and receiver.
The Long Path (Red Dotted Line): This dotted red path takes the scenic route, circling
the globe to connect the locations.

A small blue circle marks the geographical midpoint along each path, providing a visualreference for understanding the distances between the transmitter and receiver.

The Data Bar
Beneath the map lies your personalized propagation command center, a dynamic data bar that
updates in real-time as you adjust your transmitter and receiver locations. This information-richdisplay provides:
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Precise Coordinates: Latitude and longitude for both your transmitter and receiver,
ensuring pinpoint accuracy.
Distance at a Glance: See the total distance between your locations for both the shortpath and long path, displayed in both kilometers and miles.
Bearing for Optimal Aiming: Determine the precise bearing (from True North) via boththe short path and long path, enabling you to optimize your antenna orientation for
maximum signal strength.
Midpoint Coordinates: The latitude and longitude of the geographical midpoint for both
paths are provided.

The latitude and longitude of Transmitter (in degrees)
The latitude and longitude of Receiver (in degrees)
The Short Path distance from Transmitter to Receiver in kilometers and miles
Short Path bearings. The first value: the bearing (in degrees) from True North fromTransmitter to Receiver. The second value: the bearing (in degrees) from True North from
Receiver to Transmitter.

55. The latitude and longitude of the geographical midpoint of the circuit from Transmitter
to Receiver via Short Path
6. The Long Path distance from Transmitter to Receiver in kilometers and miles
7. Long Path bearings. The first value: the bearing (in degrees) from True North fromTransmitter to Receiver. The second value: the bearing (in degrees) from True North from
Receiver to Transmitter.
8. The latitude and longitude of the geographical midpoint of the circuit from Transmitter
to Receiver via Long Path

Setting the Date and Grayline Terminator
Understanding HF propagation requires more than just knowing your location; it demands a
grasp of time itself. VOACAP Online gives you the power to manipulate time, allowing you tovisualize the movement of the grayline terminator for any date and time.

Your Time Machine: The Pop-Up Calendar
A user-friendly calendar, nestled in the bottom-left corner of the map, serves as your timemachine. To embark on your temporal journey:
1. Click to Open: Click on the calendar date field (or the black downward arrow beside it,
depending on your browser) to reveal the calendar interface.
2. Navigate Through Time: Use the left and right arrow icons to effortlessly browse
through months and years, selecting your desired month.
3. Choose Your Date: Click on any day within your chosen month. This sets the date used
for the grayline terminator, and the month set will be used for calculating propagation
predictions. The day of the month is not used for calculations in any way, as VOACAP
does not provide real-time or daily predictions.

The Time Slider
But your control over time doesn't end there! A dynamic time slider, positioned above thecalendar, allows you to manipulate the very flow of day and night:

Slide Through the Hours: Drag the slider left or right to adjust the time of day, watchingas the grayline terminator (the boundary between day and night) gracefully dancesacross the map.
UTC Time Display: The current UTC time, linked to the slider position, is conveniently
displayed to the left of the time slider.

This interactive time control empowers you to visualize how day and night shift throughout theday, assisting you in finding the optimal communication windows, especially on low bands, foryour chosen date/month and location.

Sunrise and Sunset Insights
At the top of the interactive map, three sets of colorful circles (red, blue-bordered green and red,and blue) provide a crucial layer of information for optimizing your HF communication strategy:
sunrise, sunset, and midnight times.

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Red Circles (Transmitter): These circles reveal the precise UTC sunrise, sunset, andmidnight times for your chosen transmitter location.
Blue-bordered Circles (Short-Path/Long-Path Midpoints): Discover the sunrise,sunset, and midnight times at the geographical midpoint of the short-path/long-path
propagation path.
Blue Circles (Receiver): Uncover the sunrise, sunset, and midnight times for your chosen
receiver location.

Click on any of the sunrise, sunset, or midnight circles to witness the magic unfold on the map
below. The grayline terminator will dynamically adjust to display its position at the selected
time, providing a visual representation of day/night boundaries across the globe.
This interactive feature, inspired by the pioneering work of Steve G0KYA, empowers you to
pinpoint the optimal times for exploiting grayline propagation and unlocking enhanced lowband signals. For even deeper insights into grayline propagation, be sure to explore the green
DXCC Grayline button.

Navigating the Input Parameters
VOACAP Online puts you in the driver's seat, allowing you to fine-tune your propagation
predictions with a range of customizable parameters. These controls, conveniently located on
the left and right sides of the interactive map, empower you to tailor the analysis to your specificneeds.

Left-Side Controls
The left side of the map presents a suite of essential controls for customizing your predictions:

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QSO Window Markers: Toggle the icon to show or hide five red markers (labeled A to E).
Hover over a marker to view its label. Position the markers as needed for QSO Window
and Planner DIY analyses.
Set Home: Establish your home base by saving your preferred transmitter and receiverlocations, along with your chosen antenna configurations, as a convenient cookie. Thiseliminates the need to re-enter this information every time you visit. Click Unset Home
to clear these saved settings.
Short/Long Path (Default: SP): Toggle between analyzing propagation along the greatcircle Short Path (SP) or Long Path (LP) with a single click. This setting also influences
many of the calculations performed by the green buttons beneath the map.
Sporadic-E Layer (Es) (Default: NoEs): Account for the potential impact of sporadic-E
propagation, particularly during summer months when this phenomenon can beprevalent. While the default setting is OFF (NoEs) due to the sporadic-E model not being
fully tested during VOACAP's development, you can enable it if desired. Keep in mind that
sporadic-E effects are not entirely excluded from VOACAP calculations, even when thissetting is OFF.
Maidenhead Grid Overlay (Default: NoM): Enhance your map visualization by toggling
the Maidenhead grid overlay ON or OFF. This grid provides a convenient reference forquickly identifying locations based on their grid squares.

Right-Side Controls
On the right side of the map, you'll find controls that allow you to fine-tune the characteristics ofyour transmitted signal.
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Transmitting Mode: Select your desired operating mode from a dropdown menu
featuring popular options such as WSPR, FT8, CW, SSB, and AM. CW is set as the default
mode.
Transmitting Power: Choose your desired power level from a range of options, spanningfrom a modest 0.1 watts to a robust 1500 watts (the default setting), and up to 20 kW. To
account for real-world line losses, the tool automatically factors in an 80% efficiency,
meaning your selected power is adjusted accordingly for the calculations.
Antennas: This button unveils a world of antenna possibilities. Select a different antenna
for each amateur radio band, tailoring your setup for optimal performance across the
spectrum.
Settings: Customize the fundamental parameters used for all propagation predictions.
Clicking it reveals an overlay window, conveniently sliding in from the left side of themap, containing five distinct setting groups. This allows you to tailor your predictions toyour specific needs, ensuring accurate and relevant results.

Important Considerations for Antenna Selection
While the tool provides a wide array of antenna choices, it's important to remember that these
are idealized, omnidirectional representations. This deliberate simplification allows you tovisualize potential openings to all corners of the globe without the constraints of real-worldantenna patterns.

8When choosing your virtual antennas, prioritize:Elevation Angle: Consider the typical elevation angles and select antennas that perform
well at those angles.
Gain: Higher-gain antennas can provide a significant advantage in signal strength,
particularly for challenging long-distance communication.

Swap TX/RX Antennas: For quick comparisons and experimentation, conveniently swap yourchosen transmitter and receiver antennas with a single click using the Swap TX/RX antennas
button.

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Settings for Precision Control
VOACAP Online goes beyond basic predictions, offering a sophisticated suite of settings thatallow you to fine-tune every aspect of your analysis. Clicking the Settings button on the rightside of the map unveils an overlay menu, your portal to five distinct parameter sections:
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General Propagation Settings: Fine-tune the fundamental parameters that influence all
propagation calculations.
Coverage Area Map Settings: Customize the generation of coverage area maps forvisualizing signal reach.
Propagation Planner Settings: Tailor the analysis performed by the Propagation
Planner for strategic planning.
TX Antenna Analysis Settings: Compare the performance of different transmitting
antennas for your chosen path.
Take-off Angle Analysis Settings: Evaluate how well your selected antennas align withpredicted take-off angles.

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Let's delve into the intricacies of each section:
1. General Propagation Settings
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Noise: Simulate real-world conditions by defining the noise level at the receiver end of
the circuit. Choose from presets ranging from "Noisy" (extensive noise) and "Remote"(minimal noise). “Quiet” is the default setting. This setting influences QSO probabilities,
with lower noise generally leading to higher probabilities of successful communication.
Smoothed Sunspot Number (SSN): For advanced users, this setting allows manualcontrol over the SSN used in calculations. Set by default to -1, VOACAP Online
automatically utilizes predicted smoothed SSN values for up to 9 months into the future.
However, you can override this and input specific SSN values for specialized analysis or
historical simulations. Remember that VOACAP relies on smoothed monthly SSN figuresrather than daily values, as it is not designed for real-time predictions. For the mostaccurate results, adhere to the Lincoln-McNish smoothed SSN figures provided by WDCSILSO.
Dynamic SSN: For situations where recent solar activity significantly deviates frompredicted monthly averages, enable this experimental option to utilize a running threeday average of daily sunspot numbers.
Propagation Model (Method): Select your desired VOACAP propagation model:
 Auto (Default): This intelligent mode, referred to as Method 30 in VOACAP
terminology, acts as your autopilot. It automatically selects either the ray-hop or
ducted model based on the distance between your transmitter and receiver,
ensuring optimal prediction accuracy. For paths exceeding 7,000 km, a smoothing
function is applied to enhance prediction reliability.
 Ducted: Force the use of the ducted (forward-scatter) model, typically suitable forpaths exceeding 10,000 km. This mechanism, prevalent in paths with three ormore ionospheric hops, involves signals being trapped within layers of theionosphere and guided over long distances. For shorter paths where ray-hop
propagation dominates, this model may produce less accurate results.
 Ray-hop: Employ the classic ray-hop propagation mechanism, best suited forshorter paths generally under 10,000 km. It accounts for multiple reflections
between the ionosphere and Earth's surface, factoring in signal losses incurred
during each hop. While highly accurate for shorter to medium distances, thismodel may produce overly pessimistic predictions for paths beyond the third
ionospheric hop, where ducting mechanisms can significantly enhance signal
propagation.
Minimum Take-off Angle (Min. TOA): Define the lowest takeoff or arrival angle
considered for antenna analysis. The default setting of 3.0 degrees can be a good choice
in typical cases. However, if you employ highly efficient antennas with very low takeoffangles, consider lowering this value to 0.1 degrees to capture potential low-angle
propagation modes. Experimenting with this setting can reveal optimal values for yourspecific antenna setup.

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Deep Dive into the Importance of the Minimum Take-off Angle Setting
VOACAP's calculations involve analyzing various propagation modes, each associated with a
specific range of take-off angles. By setting the Minimum TOA, you're essentially instructing
VOACAP to focus its analysis on modes that fall within a certain angular range.
Here's why this matters:Missing Optimal Modes: Setting an overly low Minimum TOA (e.g., 0.1 degrees) withantennas designed for higher take-off angles can lead to VOACAP overlooking the mostefficient propagation modes. Since VOACAP typically analyzes only three modes perionospheric layer, starting at a very low angle might cause it to miss higher-angle modes
that align better with your antenna's capabilities.
Real-World Terrain Considerations: A Minimum TOA of 3.0 degrees is often
recommended as a balanced starting point. This value accounts for the fact that skywave
signals rarely arrive at extremely low angles due to terrain irregularities and obstructions.
Antenna Characteristics: The ideal Minimum TOA setting depends heavily on yourantenna setup. For highly efficient antennas designed for low-angle radiation, a lower
Minimum TOA (e.g., 0.1 degrees) might be appropriate. However, for antennas withhigher take-off angles, a Minimum TOA of 3.0 degrees or higher often yields moreaccurate results.

Finding Your Optimal Minimum TOA
Don't be afraid to experiment! VOACAP Online encourages exploration. Try running predictions
with different Minimum TOA values between 0.1 and 3.0 degrees, observing how the resultschange based on your chosen antennas and propagation paths. This hands-on approach will
help you determine the optimal setting for your specific HF setup, ensuring the most accurate
and insightful predictions.
2. Coverage Area Map Settings
VOACAP Online recognizes that generating accurate and insightful coverage area maps requires
flexibility. Therefore, you have dedicated control over key parameters, allowing you to tailor the
analysis to your specific needs.
Key ParametersYear and Month: The desired year and month for your coverage area analysis will beread from the calendar.
UTC Time: Define the starting hour (in UTC) for your maps. By default, this is set to thecurrent UTC hour.
Range (Plotting Time Range): Determine the time span you want to visualize on yourmaps, up to a maximum of 9 hours. Opting for a number of shorter runs ensuressmoother processing and optimal performance. Keep in mind that even exceeding 6
hours might lead to timeouts, depending on server load.

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3. Propagation Planner Settings
Maximize your success in HF contesting and DXing by strategically planning your sessions totake advantage of every propagation opportunity.
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DX Sites: Choose your target regions for analysis, selecting from CQ Zones, ITU Zones, or
specific DXCC countries and entities grouped by continent. The Propagation Planner
utilizes your chosen settings for antennas, short/long path selection, sporadic-E,
transmission mode, and power to generate comprehensive predictions for your desired
locations.

4. TX Antenna Analysis and Take-oﬀ Angle Analysis Settings
VOACAP Online empowers you to go beyond simply selecting antennas; it provides the tools toanalyze and optimize their use for your specific propagation needs.
TX (Transmit) Antenna Analysis: Finding the Right Antenna for the Job
Within the "TX Antenna Analysis Settings" section, you can unleash the power of comparative
analysis. Compare the performance of various transmitting antennas for your defined circuit andchosen month. Select from a diverse range of antenna types, including isotropic, dipoles, andYagis, at various heights. Note that this analysis temporarily overrides your user-defined TX
antennas, but your selected RX (receive) antennas for each band remain unchanged.
In many comparisons, various vertical antennas are compared to a number of dipoles and Yagi
antennas to give insights into their performance.
How it works:
1. Antenna Selection: Choose from a comprehensive list of antenna types, including: ISOTROPE: The theoretical benchmark, an isotropic antenna radiates equally inall directions with 0 dBi gain.
 HVD025: A half-wave vertical dipole fed at 0.25 wavelengths above ground level.
 Vertical Antennas (V14, V14GD, V14VYGD, V32, V58): Various vertical antennas
with different lengths and ground conditions: Average, Good (GD) and Very Good(VYGD) grounds.
 Horizontal Dipoles (DxxM): Horizontal half-wave dipoles at user-defined heights(xx meters above ground level).
 Yagi Antennas (3ELxxM, 5ELxxM, 7ELxxM): Horizontal Yagi antennas withvarying element counts (3, 5, or 7) and heights (xx meters above ground level).
2. Initiate Analysis: Click the "Antenna" button below the world map to run the analysis.
VOACAP Online will simulate propagation using each selected antenna, providing
insights into their relative performance.

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Take-off Angle Analysis: Aligning Your Antennas with Propagation
The "Take-off Angle Analysis Settings" section helps you understand how well your chosenantennas align with the predicted take-off angles for your circuit.
Fine-tuning Your Analysis:Time Period: Choose to analyze take-off angles for the entire year or focus on theselected month for a more targeted assessment.

Running the Analysis:Click the TO Angle button below the world map to initiate the analysis. This process willcalculate the optimal take-off angles for your circuit and provide insights into how wellyour selected antennas match those angles.

By leveraging these powerful analysis tools, you can make informed decisions about yourantenna selection, ensuring your HF station is optimized for maximum performance and signal
propagation.

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Your HF Toolkit: The Deep DiveVOACAP Online doesn't just crunch numbers; it transforms them into insightful visualizations
that deepen your understanding of HF propagation. It offers an impressive arsenal of 16 distinct
services, each accessible via clickable buttons beneath the world map, or on the right side of themap. These services encompass both point-to-point predictions, focusing on specific TX/RX
pairs, and coverage area maps, which visualize signal propagation over broader geographicalregions.
Each green prediction button opens a new window dedicated to its specific analysis, providing
detailed results and visualizations to empower your HF explorations. Whether you're seeking
optimal communication windows, exploring long-path propagation, or analyzing antenna
performance, VOACAP Online equips you with the tools to navigate the fascinating world of HF
radio with confidence and precision.

1. Prop Charts & Prop Wheel
Prop Charts
Clicking the Propagation Charts (Prop Charts) button on the right side of the map reveals 15
interactive charts covering amateur radio bands from 3.5 MHz to 28 MHz. These charts provide
valuable insights into predicted propagation conditions between your chosen transmitter (TX)
and receiver (RX) locations.

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Visualizing multiple output parameters on interactive charts enhances our understanding of HF
propagation, offering a much richer picture than a single parameter alone. For a truly
comprehensive assessment, three key parameters – REL (Circuit reliability), SDBW (Signal
power), and MUFday – are essential:
REL (Circuit reliability): Expressed as a percentage, REL indicates the likelihood of successfulcommunication (QSO) on a given frequency and time. A higher REL means a greater chance ofclear, reliable communication.
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REL is directly linked to SNR (Signal-to-Noise Ratio) and REQ.SNR (Required Signal-toNoise Ratio), acting as a circuit reliability factor.
It represents the percentage of days within a month when the SNR value (not shown
separately in the charts) reaches or exceeds the REQ.SNR.
REQ.SNR, an internally defined value, is tied to the chosen transmitting mode. For
example, for CW, it is set to 19 dB-Hz, while for SSB it is 38 dB-Hz. All transmitting modes
have internal threshold values of their own.

SDBW (Signal power): SDBW represents the predicted median signal strength at the receiver.
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The green line on the chart represents the predicted dBW (decibels relative to one watt)value that can be maintained on 50% of the days (15 days out of the month).
The SDBW distribution, shown as a light-gray area above and below the green SDBW line,
reveals the expected signal power levels at the receiver throughout the month, for a
specific frequency and hour.
SDBW90 (90% of days, 27 days) and SDBW10 (10% of days, 3 days) mark the upper andlower boundaries of the light-gray area, indicating the range of potential signal strength.
It's important to note that these values don't specify which days will be good or bad, butrather, the overall range of possibilities.
Use the SDBW to S-Meter conversion table to convert the SDBW values to S-meterreadings: https://www.voacap.com/2023/understanding/s-meter.html

MUFday: This parameter reveals the percentage of days in a month, at the given hour, when theoperating frequency will be below the predicted median Maximum Usable Frequency (MUF) for
the Most Reliable Mode (MRM).
The MRM is the mode of propagation with the highest reliability of achieving the required
SNR (REQ.SNR).

Data Presentation

REL and MUFday data are expressed as percentages from 0 to 100.
SDBW data is presented in dBW values, ranging from -164 (extremely low noise level)to -103 (corresponding to an S-meter reading of S9).
Each step in the SDBW scale corresponds to 6 dB or one S-meter reading step.

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Short-Path and Long-Path Considerations
It is important to remember that all three parameters are calculated using both Short-Path andLong-Path propagation paths. This provides a comprehensive view of the potential propagation
conditions for a given communication scenario.
Interactive Charts for Enhanced Analysis
The charts present multi-colored lines representing each parameter, and you can toggle thevisibility of individual parameters and frequencies directly from the legend, allowing them tofocus on the most relevant information. Additionally, a robust toolbox provides a suite offeatures for further exploration, including:Saving as PNG: Capture and share your insights with ease.
Zooming: Dive into specific areas of interest for detailed analysis.
Data Comparison: Hover over any point to compare results across all frequencies.
Panning: Explore the chart freely for a comprehensive view.

Predicting Prime Time for Radio Communication
Propagation Graphs are your essential guide to understanding the nuances of radio
communication, helping you choose the optimal time and frequency for your transmissions.

Let's decode the visual clues in a band-specific propagation chart:

The Blue Line (REL, Reliability): Like a quick weather forecast, the blue line reveals theprobability of successful communication via the short path, hour by hour. It offers a quick
glance at propagation possibilities.
The Orange Line (MUFday): This line acts like a frequency guide, showing theprobability of your chosen frequency staying below the calculated MUF (Maximum
Usable Frequency) for the short path.

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The Green Line (SDBW, Signal Power): This green line unveils the median signal
strength for 15 days of the month via the short path. The corresponding S-meter scale isshown on the right of the chart.

The Gray Zone: Dive into the gray zone above and below the green line for a glimpse into thevariation of the predicted signal strength via the short path. The upper edge hints at thestrongest signal you might encounter on those lucky 3 days (10% of the time), while the lower
edge reveals the minimum signal strength you can expect on those more frequent 27 days (90%of the time).
When the gray zone widens, uncertainty creeps in. A gap or spread of 40-50 dB means
VOACAP is unsure of the future. Such a vast range can signify a high degree of uncertainty in the
propagation prediction. But when the gap narrows, you're looking at better prediction accuracy
and a brighter chance of communication.
In our example chart, VOACAP's prediction for such a wide distribution implies that 80% of thedays within a month (as defined by SDBW90 and SDBW10) could experience Signal Power levels
anywhere between below noise and S7 – a staggering 50 dB difference! If VOACAP could speak, it
would likely express its own uncertainty about the expected conditions on that frequency atthat hour.
Prime Time for Communication: The best times to connect are those with:

a high lower edge of the grey zone (a strong signal on most days)a soaring orange line (high probability of staying below the MUF), ideally over 50%
a robust green line (good signal strength for 15 days in a month)

Don't forget: LP in the graphs stands for propagation via the long path.
Now, equipped with this visual language, you can decipher the clues of VOACAP and find those
perfect communication windows.

Prop Wheel
The Propagation Wheel (Prop Wheel) on the right side of the map will provide a quick andintuitive overview of propagation potential with its iconic 24-hour clock. This dynamic wheel
displays the REL (Circuit Reliability) parameter for all amateur bands, using a color-coded
system to represent the probability of successful communication throughout the day. Keep thiswindow open as you experiment with different TX/RX locations and settings, and watch as thepredictions update on-the-fly, providing instant feedback and insights.

18Note about times: The Propagation Wheel is designed to provide an intuitive representation ofhourly predictions. Here's how to interpret it: the hour mark on the outer ring signifies the top of
the hour. Each hour segment is divided equally, representing a 30-minute interval before andafter the hour mark. For instance, when you look at the prediction labeled as 07 UTC, it
encompasses the time period from 06:30 to 07:30 UTC!

Getting Started with Propagation Prediction Analysis
1. Start with REL: Use the Propagation Wheel to quickly identify bands with the highest
REL values for your desired path.
2. Analyze SDBW: Navigate to the Propagation Charts and examine the SDBW values forthe bands shortlisted in the previous step. Look for bands with higher SDBW values andnarrower distributions, indicating stronger and more consistent signals.
3. In-depth Analysis with Band-Specific Charts: For further analysis, focus on the charts
for your chosen bands. Pay close attention to MUFday values and the SDBW distribution.
Be wary of extremely wide SDBW distributions, as these suggest less reliable predictions.
4. Don't Forget Long-Path: Explore both Short-Path and Long-Path predictions, especiallyfor long-distance communication, as Long-Path propagation can sometimes offer
unexpected opportunities.

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2. Band-by-band: The Big PictureEver wished you could see the full HF picture at once? Based on the Propagation Charts analysis
above, the Band-by-band button grants you that wish, presenting all 15 prediction charts andboth short-path and long-path propagation tables in one, easy-to-absorb layout. Get ready for
an "Aha!" moment as you uncover hidden propagation opportunities across the entire
spectrum.

3. REL | SDBW | SNR: Three-in-One Predictions
The REL | SDBW | SNR graphs provide a comprehensive overview of predicted propagation
conditions for your chosen frequency and path. This section guides you through interpreting thedata.

Generating the Graphs
Clicking the REL | SDBW | SNR button initiates a detailed calculation for the entire frequency
range of 2 MHz to 30 MHz. This generates three key graphs:REL (Circuit Reliability): This graph, further detailed below, illustrates the probability ofsuccessful communication.
S DBW (Signal Power): This graph displays the predicted signal strength at the receiver.
SNR (Signal-to-Noise Ratio): This graph depicts the signal strength relative tobackground noise.

Key FeaturesMedian MUF (Maximum Usable Frequency): Represented by the black curve, thisindicates the highest frequency likely to provide stable communication.
FOT (Frequency of Optimum Traffic): The blue curve highlights the frequency predicted
to offer the most reliable communication.

20

4. Best FREQ: Guide to Optimal Frequency Selection
The Best FREQ feature is your secret weapon for identifying the prime operating frequencies foreach hour of the day, throughout the entire month! It analyzes all ham radio bands, taking theguesswork out of finding the optimal frequencies for your chosen circuit.

Here's how it works:
1. Best FREQ in Action: After careful analysis, the three most promising bands arepresented: FREQ1, FREQ2, and FREQ3.
2. Decoding the Results: The output page displays the top three frequencies alongside
crucial performance indicators for each UTC hour: SDBW (Signal Power): The median signal strength (in dBW) achievable on 50% of
the days. The S-Meter Signal Strength is conveniently displayed in parentheses.
 REL (Circuit Reliability): The percentage of days in the month with a Signal-toNoise Ratio (SNR) meeting your chosen mode's threshold. Higher reliability
means more consistent communication.
 SNR (Signal-to-Noise Ratio): The median SNR achievable on 50% of the days. A
higher SNR translates to a more reliable communication.
 MUFday: This indicates the percentage of days when the frequency falls below
the predicted MUF.

21

FOT (Frequency of Optimum Traffic): This is the frequency where
communication is achievable on 90% of the days (= 27 days), representing
another highly reliable choice.
 MUF (Median Maximum Usable Frequency): This represents the frequency
supported by the ionosphere on 50% of the days (= 15 days).
 HPF (Highest Possible Frequency): This is the frequency where communicationis possible on 10% of the days (= 3 days), representing a less reliable option.
3. Prioritizing Performance: While FOT, MUF, and HPF offer valuable insights, the mostaccurate predictions come from considering Signal Power, Circuit Reliability, andSignal-to-Noise Ratio together. Best FREQ leverages all these factors to pinpoint the
optimal frequency for each hour.
Interpreting the Signs
To help you quickly assess potential issues with the Best Frequency, pay attention to these
indicators:(-) Minus: The predicted SNR is below zero, indicating potential signal issues.
(+) Plus: The REL value is below 10%, but the median Signal Power (SDBW) still remains
slightly above the noise floor.
(*) Star: The REL value is below 10%, and the median Signal Power (SDBW) is close to or
below the noise floor, suggesting challenging conditions.

Important Note: The SDBW, REL, SNR and MUFday values displayed apply only to the best
frequency, FREQ1. If the best frequency is flagged, the second and third best frequencies areunlikely to offer better performance and may be significantly worse.

5. Total: Detailed Propagation Statistics
After meticulously setting your transmitter and receiver locations and fine-tuning otherparameters, you're ready to unlock a wealth of propagation insights. Click the green Total
button nestled below the world map – this is your gateway to a comprehensive analysis of yourcommunication circuit.
Unpacking the Treasures: Understanding Your Report
The report presents data meticulously calculated for each hour of the day, from 01:00 to 24:00
UTC. This data empowers you to make informed decisions about your radio communication
setup.
Key Propagation Metrics


MUFday: A Frequency Gauge
Imagine this: you're aiming to transmit on a specific frequency. MUFday tells you, foreach hour, what percentage of the month this frequency will be below the predicted
median Maximum Usable Frequency (MUF) for the Most Reliable Mode (MRM). In simpler
terms, a higher MUFday percentage increases the likelihood of your chosen frequency
22

being usable for successful communication. Keep in mind that a favorable MUFday alone
doesn't guarantee a good connection. You'll also need to consider other crucial factors
like a high level of reliability (REL) and sufficient signal strength (SDBW) to ensure clear
and consistent communication.
REL (Circuit Reliability): The Confidence Builder
This figure cuts to the chase – it represents the likelihood of establishing successfulcommunication on your chosen frequency and time. A higher REL translates to a morereliable connection.



SNR (Signal-to-Noise Ratio): The Clarity IndicatorThink of SNR as the clarity of your transmission. The report provides SNR predictions atthree distinct confidence levels, painting a comprehensive picture:
o
o
o



SNR10 (Optimistic): This reflects the best-case scenario – the best predicted SNR
achievable on a mere 10% of the days (i.e., 3 days) in the month.
SNR50 (Typical): This represents the median expectation – the SNR you cananticipate on 15 days in the month.
SNR90 (Conservative): This provides a realistic lower limit – the SNR achievable
on 90% of the days (i.e., 27 days) in the month.

SDBW (Signal Power at Receiver): The Strength Barometer
Similar to SNR, SDBW measures the strength of your signal as it reaches the receiver. It's
also presented at three confidence levels:ooo

SDBW10 (Optimistic): The most optimistic prediction - the signal strengthachievable on 10% of the days, i.e. 3 days in the month.
SDBW50 (Typical): The median signal strength you can expect on 15 days month.
SDBW90 (Conservative): The minimum signal strength you can reasonably
anticipate on 27 days in the month.

Data Presentation: Navigating Your Report with Ease
To make this wealth of data easily digestible, the report is structured in two user-friendly
ways:
1. Tabulated by Parameter
The data is initially organized into clear tables, with each table dedicated to the specificparameters: MUFday, REL, SNR and SDBW. This allows you to quickly hone in on themetrics most relevant to your needs.
2. Organized by Amateur BandFor amateur radio enthusiasts, the report then presents the data grouped by HF amateur
bands. This provides a convenient overview of propagation conditions on your preferredfrequencies. Two additional parameters further enhance this view:

23

o

o

dSNR (SNR Range): This value represents the difference between SNR10 and
SNR90, essentially showing the expected fluctuation in signal clarity throughout
the month.
dSDBW (Signal Strength Range): This figure illustrates the difference between
SDBW10 and SDBW90, providing an understanding of the potential variation insignal strength.

Raw VOACAP Output: Delving Deeper
For seasoned users who crave the nitty-gritty details, the report concludes with a link to theraw data output from the VOACAP engine. This allows for in-depth analysis andcustomization for experienced users.

6. All-Year Propagation Predictions
The All-Year Prediction (the Year button) tool provides a powerful way to visualize HF
propagation conditions for an entire year. Let's break down how to interpret this valuable data.

This prediction calculates point-to-point propagation between your chosen transmitter (TX) andreceiver (RX) location, spanning a full year. The tool leverages the latest Sunspot Number
predictions for each month of the year from SIDC in Belgium to provide the most accurate
forecast.

24

Each hourly prediction covers a 60-minute window centered on the displayed hour. For
example, 01 UTC represents the period from 00:30 to 01:30 UTC.
At the top of each table, you'll find:






TX and RX location labels
Short-path (SP) or Long-path (LP) indication
Circuit distance in kilometers and miles
Bearing from TX to RX in degrees from True North
Sunspot Number (SSN) used for calculations

Color-Coded Probability
The prediction tables utilize a color gradient to represent the probability of establishing a
successful contact. You will see the color code with percentages at the top and the bottom of theprediction window.








White: 0% probability
Blueish: 10% probability
Greenish: 30-40% probability
Yellowish: 50-60% probability
Yellow-Orangeish: 70-80% probability
Orange-Reddish: 90% probability
Red: 100% probability

Gray Areas
The color gray requires special attention. On lower frequencies, gray indicates that while
VOACAP doesn't predict a high probability of contact (REL), there's still predicted signal power(SDBW). This suggests a "gray area" where successful communication might be possible.
On higher frequencies, gray typically signifies poor probabilities above the Maximum Usable
Frequency (MUF). While VOACAP might show some potential, the actual conditions are likely
unfavorable.
Key Parameters
Three crucial parameters are displayed within each hourly cell, visible at a mouse hover:

R (Reliability): VOACAP's calculated probability of a successful QSO (contact) expressed
as a percentage.

S (Signal Power): Estimated signal strength in dBW. Use the SDBW to S-Meter
conversion table to convert the SDBW values to S-meter readings:
https://www.voacap.com/2023/understanding/s-meter.html

M (MUFday): This percentage represents the likelihood of the operating frequency being
below the MUF for that specific hour. A higher MUFday value generally indicates better
communication if the two other parameters are also favorable.

25

Sunrise/Sunset Visualization
For added convenience, the tables visually represent sunrise and sunset times for both TX, RX
and circuit geographical midpoint (MP) locations. The sunrise and sunset times are calculatedfor Day 15 of each month. Dark gray signifies nighttime, while white represents daytime. Hover
your mouse over the TX/RX/MP labels to view precise sunrise and sunset times in UTC.

7. QSO Window: Your Secret Weapon for DX Success
Chasing that rare DX contact? It's a race against propagation and a battle against competing
stations. But what if you had a secret weapon, a way to predict the optimal time to make yourmove? Enter the QSO Window, a game-changing feature inspired by DX veterans Risto OH3UUand Cesar PY2YP. Set your QSO Window markers to the map, and click on the green QSOWindow button to start!
Imagine this: you've pinpointed your target DX station on an interactive map. Now, activate the
QSO Window and watch as five additional markers appear, representing potential competitors
also vying for that coveted contact. The magic? The QSO Window runs live propagation
predictions from all six stations (yours and the five competitors) to the DX station, displaying theresults as dynamic, easy-to-compare charts.
Ready to dive deeper into the QSO Window and unlock its full potential? Let's break down its
features and benefits, empowering you to strategize your DX contacts like never before.
1. Unveiling the Competitive Landscape
The QSO Window's magic lies in its ability to simulate a real-world DX pileup. Input your location
as the Transmitter (TX) and the DX station as the Receiver (RX). Strategically position the fivecompetitor markers (A to E) to reflect common rivals (think US coasts, Europe, Japan) or
customize them based on your target, all vying for the same DX station. Now, this allows you to:

Identify Prime Time: Determine the optimal UTC hours when your signal stands out
from the crowd, maximizing your chances of a successful QSO.
Anticipate Challenges: Be prepared for periods of increased competition and adjust
your strategy accordingly.
Exploit Propagation Advantages: Capitalize on fleeting openings where your location
enjoys a temporary advantage over others.

2. Harnessing the Power of VOACAP Data
The QSO Window presents the VOACAP data in an intuitive and actionable format. Each graphprovides unique insights:Median Power (SDBW): Visualize your signal strength at the DX station relative to otherstations. Higher values on the S-meter scale indicate a stronger signal and a betterchance of being heard.
Reliability (REL): Gauge the consistency of your signal path. Higher percentages indicate
a more reliable QSO.

26

Median Signal-to-Noise Ratio (SNR): This is the critical factor for successfulcommunication. In case of CW, the higher your SNR above the 19 dB/Hz threshold (thered dotted line in the charts), the more powerful your signal will be amidst the noise.

3. Mastering the Interactive Interface
The QSO Window empowers you with:

Short/Long Path Analysis: The header displays whether the short or long path isselected, along with distance and bearing to the DX station.
Competitor Coordinates: Easily view the coordinates of all five competitor stations (A to
E) in the results header.

The QSO Window's intuitive design empowers you to manipulate data and customize your view:

Dynamic Graphs: Hover over any point on the graphs to reveal precise values for eachstation at a specific UTC hour.
Customizable Visibility: Toggle station visibility by clicking on their correspondingcolors in the legend, decluttering the graphs and focusing on your key competitors.
Strategic Marker Placement: Fine-tune the simulation by strategically positioning thefive competitor markers on the map (via the QSO marker icon on the left-side controls) toreflect realistic scenarios or target specific regions.

Remember, the QSO Window is a powerful tool that complements your existing knowledge andexperience. Consider these additional factors when interpreting the data:Antenna Performance: The simulation assumes identical antennas for all stations. Your
actual antenna setup can significantly impact your results.
Propagation Variability: While VOACAP provides accurate predictions, real-world
propagation can fluctuate. Remain adaptable and use the QSO Window as a guide.
Operating Skills: Strong operating skills, including efficient calling practices and clear
audio, remain crucial for securing DX contacts, even with favorable propagation.

8. Antenna: Comparative Antenna Performance Analysis
The green Antenna button beneath the world map acts as your gateway to a comprehensive
exploration of your antenna setup. Clicking it sets in motion a comparative study, meticulously
analyzing your chosen transmit antennas and revealing their potential across the entire HF
spectrum, based on the circuit and input parameters of your choice.
Unveiling the Best Reliability
First, we embark on a quest for the highest reliability across the amateur bands, from 3 to 28
MHz. Every transmit antenna you've selected will be evaluated for every hour of the day, utilizing
your chosen receive antennas. This analysis, however, doesn't reveal the specific band where
this peak reliability occurs; instead, it presents the absolute maximum reliability achievable withyour chosen antennas across the entire HF spectrum. A clear color-coding system within thetable cells will highlight the best reliability values, making the results instantly digestible.

27

Optimizing Frequency Selection: A Quest for the Best SNR
Next, we turn our attention to maximizing the signal strength to noise. The Best Frequency by
Hour analysis scrutinizes the Signal-to-Noise Ratio (SNR) for each of your antennas, across allamateur bands and UTC hours. The results are elegantly presented in a table, revealing theantenna with the highest SNR and the corresponding frequency where this peak performanceoccurs for each hour. Like the reliability analysis, a color-coded system within the table cells
highlights the best SNR values for eﬀortless comprehension.
Delving Deeper: Unveiling the Power of Signal Power and SNR
Beyond these initial comparative studies, a treasure trove of in-depth analysis awaits. A
meticulous examination of Signal Power and SNR for each selected antenna is presented, broken
down by both hour and amateur band. This granular view empowers you to truly understand thenuances of your antenna performance, identifying optimal operating frequencies and hours foreach antenna within your setup.
For the Data-Driven Explorer: CSV Export
For those who crave even deeper insight, the results are readily available in CSV format. This
allows you to seamlessly transfer the data to Excel, where you can perform advanced analysis,
create custom visualizations, and uncover hidden trends within your antenna performance. The
possibilities are endless!

9. TO Angle: A Journey into Take-Oﬀ Angles
The green TO Angle button unlocks a powerful tool for understanding the performance of yourantennas in the context of real-world propagation. Click it, and you'll embark on a journey touncover the "take-oﬀ angles" – the angles at which radio waves leave your antenna – and how
they align with the optimal angles for successful communication.

28

A Deep Dive into Angles
First, VOACAP calculates the predicted take-oﬀ angles for each of your chosen transmit antennas
across the entire amateur band spectrum (3 to 28 MHz). Using VOACAP Method 30, it thendetermines the optimal take-oﬀ angles needed for the most reliable propagation mode – themode that promises the best communication for your chosen circuit. This simplified approach
focuses on the most eﬀective angles only, so not all take-oﬀ angles available from otherpropagation modes are reported. You can choose to analyze the optimal take-oﬀ angles for asingle month or the entire year, giving you a comprehensive understanding of your antenna's
performance across diﬀerent seasons.
Visualizing the Perfect Match
Next, VOACAP creates a series of visual graphs, one for each amateur band. These graphs
beautifully illustrate the interplay between your antenna's theoretical take-oﬀ angle and thepredicted optimal angles for reliable communication. A red line represents your antenna's takeoﬀ angle, with the corresponding gain at that angle displayed in red on the right-side scale.
Across the graph, blue bars depict the distribution of all predicted take-oﬀ angles needed for
optimal communication, with the number of occurrences for each angle displayed in blue on theleft side.
Unveiling Antenna Suitability
By visually aligning your antenna's take-oﬀ angle pattern with the predicted optimal angles, you
can instantly grasp whether your antennas are well-suited for the chosen circuit. You can also
see how much gain your antenna provides at those optimal angles, a crucial factor for successfulcommunication.
The Ultimate Antenna Comparison Tool
This tool is a powerful resource for comparing various transmit antennas. By analyzing eachantenna's take-oﬀ angle pattern and gain against the predicted optimal angles, you can makeinformed decisions about which antenna will deliver the best performance for your specificcommunication goals.
Unlocking Deeper Insights with HFTAFor those seeking even deeper analysis, the VOACAP Take-Oﬀ Angle Analyzer allows you to
download a PRN formatted file of the elevation statistics. This file can be imported into the HFTA(High-Frequency Terrain Assessment) software, enabling you to conduct advanced analysis,taking into account the eﬀects of terrain and other factors on your signal's path.

29

10. Propagation Planner: Your Key to Contest and DX Success
By mastering the Propagation Planner (the button Planner), you gain a significant advantage inthe world of HF contesting and DXing. Plan your next operating session with confidence,knowing you're strategically positioned to make the most of every propagation opportunity.
Why Planning Matters
Imagine preparing for a big game without scouting your opponent or strategizing your plays.
That's what it's like diving into a contest or DXpedition without understanding propagation. The
Propagation Planner acts as your personal scout, revealing:

Optimal Bands and Times: Discover when and where to find the strongest openings foryour target zones.
Long-Path Opportunities: Uncover hidden propagation paths that can give you an edgein contests and DXing.
Strategic Operating Windows: Plan your operating schedule around peak propagation
times for maximum efficiency.

How the Planner Works
This online tool presents the results in two intuitive ways:
1. Zone-Based Charts: Visualize propagation predictions for both CQ and ITU zones, with
options for short-path and long-path analysis.
2. Band-Specific Zone Charts: Focus on specific bands and zones to fine-tune youroperating strategy.
Interpreting the ChartsColor-Coded Reliability: Cell colors represent the probability of making a QSO (red =highest, white = lowest).
Signal Power Indicators: Cell characters (+, ++, ●) indicate predicted signal strength and
MUFday probability. See below for their explanations.
Sunrise/Sunset Visualization: Horizontal bars below each zone-specific chart depict
day/night cycles for the TX, RX and circuit midpoint (MP) locations.
Interactive Data: Hover your mouse over any cell to reveal detailed REL (R), SDBW (S)and MUFday (M) values.

30Tips for Optimal Use

Utilize Google Chrome: For the best experience, access the Propagation Planner using
the Google Chrome browser.
Combine with Grayline Maps: Supplement low-band predictions with grayline map
software for greater accuracy.
Remember, predictions are not guarantees: While powerful, propagation predictions
are still estimations, and real-world conditions can vary.

31

Explaining the Table Colors and Characters
The cell colors reflect the predicted Reliability: red is best, white is worst. The following
characters reflect the level of Signal Power: ++, + and ●.
++ = Signal Power is S9 or more, and MUFday is 70% or more
+ = Signal Power is S6 or more, and MUFday is 50% or more
● = Signal Power is S1 or more, and MUFday is 30% or morecolored but no char = Signal is S1 or more, but MUFday is less than 30%
white = Signal Power is below or at the noise

11. Planner DIY: Your Personalized Propagation Snapshot
Want a quick and easy way to assess propagation conditions to your favorite spots around theglobe? This streamlined version of the Propagation Planner provides a personalized snapshot of
HF propagation to five locations of your choosing. Start by clicking on the Planner DIY button.
Simple Setup, Powerful Insights
Using the familiar red markers from the QSO Window, pinpoint up to five destinations on theworld map. This Planner instantly generates an easy-to-read overview, revealing propagation
potential at a glance.

32

Visualize Your Propagation LandscapeThe output provides a clear and concise summary, allowing you to quickly compare conditions
across your chosen locations. This at-a-glance view helps you:


Identify Favorable Openings: Spot potential propagation paths and time windows for
optimal communication.
Compare Signal Strengths: Assess signal quality and potential challenges for each
destination.
Make Informed Operating Decisions: Choose the best times and frequencies to connect
with your desired locations.

Whether you're chasing DX, planning a contest strategy, or simply curious about current
conditions, this five-location, quick Planner provides a user-friendly way to stay ahead of the
propagation curve.
The colors and characters used in the prediction tables are the same as in the Propagation
Planner (see “Explaining the Table Colors and Characters”).

12. P2P Grayline: Exploring Low-Band Propagation
P2P Grayline is a powerful point-to-point (P2P) tool designed to help you understand how the
sun's position affects radio propagation, especially on lower bands. It calculates sunrise, sunset,
and solar midnight times for three specific locations: your transmitter, receiver, and thegeographical midpoint along your communication path. This data is provided for both theselected month and the next month, allowing you to plan ahead and anticipate changing
conditions.

Here's how P2P Grayline works:
1. Key Times Calculated
P2P Grayline calculates seven distinct times for each of the three locations:

Sunrise-related:o DAWN: The moment the sun is 6 degrees below the horizon before sunrise.
o RISE: The actual sunrise time when the sun is at the horizon.
o POST: The moment the sun is 3 degrees above the horizon after sunrise.
33





Sunset-related:o PRE: The moment the sun is 3 degrees above the horizon before sunset.
o SET: The actual sunset time when the sun is at the horizon.
o DUSK: The moment the sun is 6 degrees below the horizon after sunset.
Solar Midnight:
o MNITE: The time opposite to solar noon when the sun is closest to the nadir,representing the middle of the night. It is dependent on longitude and time ofyear, not time zones.

2. The Importance of POST and PRE Times
These times are based on empirical observations, rather than a specific scientific theory. We
know that low-band propagation tends to weaken after sunrise and improve before sunset. The"3 degrees above the horizon" cutoff was chosen as a practical way to define these transition
periods.
3. Analyzing the Results
P2P Grayline presents these times in a clear table format, allowing you to:

Identify Optimal Communication Windows: Determine when the sun's position favors
better propagation for your circuit.
Strategize Your Operations: Plan your communication sessions around the times most
likely to yield strong signals.
Explore Grayline Propagation: Understand how the grayline terminator, the boundary
between day and night, impacts propagation conditions.

Additional NotesThe Dawn and Dusk Periods: The 6-degree threshold used for DAWN and DUSK is basedon the traditional definition of these periods.
Solar Noon: This refers to the moment the sun reaches its highest point in the sky for agiven location. Solar midnight is the exact opposite of this.
Real-World Variability: While P2P Grayline provides valuable insights, real-world
propagation is always influenced by a variety of factors. Use it as a guide to inform yourdecisions.

34

13. Exploring the Power of Coverage Area Maps
Go beyond simple point-to-point predictions and visualize your signal's potential reach with ourpowerful coverage area maps. This service allows you to generate customized maps highlighting
Circuit Reliability (REL) or Signal Power (SDBW) across the world.

Mapping Your Propagation Landscape

Multiple Parameters, One View: Explore different aspects of propagation by plotting
maps for Circuit Reliability, REL (the button REL Map) or Signal Power, SDBW (the button
SDBW Map). This comprehensive perspective helps you understand the interplay
between these key factors.
Customize Your Coverage: Fine-tune your analysis by adjusting input parameters under
the Settings button. This allows you to tailor the maps to your specific needs andoperating scenarios.
Easy Printing and Sharing: Conveniently download all generated maps from the result
page in PDF format for offline analysis or sharing with fellow enthusiasts.

Unlocking Strategic Insights
These coverage area maps empower you to:

Identify Optimal Operating Zones: Discover regions with favorable propagation
conditions for your desired frequency and time.
Plan DXpeditions and Contests: Strategically target areas with the highest probabilityof successful communication.
Visualize Signal Coverage: Understand the potential reach of your signal and identify
potential coverage gaps.

35

Important notes on the maps
Please note that generated coverage maps are periodically cleared from the server. Avoid
directly linking to these maps, as they may not be permanently accessible.

14. DXCC Grayline aka VOACAP Greyline
Want to leverage the magic of grayline propagation for your next DX contact? VOACAP Greyline(the button DXCC Grayline below the world map) is your key to understanding the sun's danceacross the globe and how it impacts your communication.
This tool provides a wealth of sun-related data for any location, specifically designed to help
DXers and contesters like you.
Here's what you can do:
1. Get Precise Sunrise and Sunset Data
 Instantly access daily sunrise, sunset, dawn, dusk, and solar midnight times for avast selection of DXCC locations.
 Understand the precise times the sun is at specific points below and above thehorizon, crucial for predicting low-band openings.
2. Plan Your Year with Custom Sun Calendars
 Generate a full-year calendar displaying sunrise and sunset times for your specificlocation.
 Easily find optimal propagation windows throughout the year.
3. Dive Deep with Grayline Analysis
 Analyze DXCC countries located along the grayline terminator or shrouded in
darkness at sunrise and sunset from your location.
 Identify prime DX targets by pinpointing locations experiencing sunrise or sunset
propagation opportunities.
 Obtain distance and bearing information for both short-path and long-path
propagation.
How to Use VOACAP Greyline:
1. Click on the green DXCC Grayline button orvisit http://www.voacap.com/greyline/index.html
2. Explore the three calculation types
 Default: Daily sunrise/sunset data for DXCC locations.
 Calendar: Full-year sunrise/sunset data for your location.
 Deep Analysis: Identify DXCC locations along the grayline terminator or in
darkness.
3. Input your Maidenhead grid locator for personalized results

36Uncover Hidden Propagation Paths
VOACAP Greyline empowers you to:Predict low-band openings with greater accuracy.
Identify optimal times for reaching specific DXCC entities.
Plan your radio operations strategically.

Read more in the VOACAP Greyline manual: https://voacap.blogspot.com/2016/11/voacapgreyline-user-manual.html

15. Space WX: Understanding Ionospheric Disturbances
The VOACAP Space Weather page provides a comprehensive overview of current and predicted
space weather conditions that can impact the ionosphere and, consequently, HF radio
propagation. This page offers a user-friendly interface to understand and interpret key space
weather indices, empowering you to anticipate potential disturbances and adjust yourcommunication strategies accordingly.
Key Space Weather Indices
The Space Weather page displays a selection of critical indices, updated in real-time, thatprovide insights into ionospheric activity:

Kyoto Dst (Disturbance Storm Time) Index: This index measures the strength of thering current around Earth, caused by solar protons and electrons. A negative Dst value
indicates a weakening of Earth's magnetic field, which can occur during solar storms andsignificantly affect HF propagation.
Proton Flux: Incoming energetic protons can enhance ionization in the lower
ionosphere, leading to increased absorption levels, particularly in polar regions. This cancompletely block ionospheric radio communications, resulting in polar cap absorption
events.
Tromso (Norway) A-Index: Calculated from K-indices measured in Tromso, this index
provides an indicator of geomagnetic activity at high latitudes. It is hoped to be a moresensitive measure of solar disturbances than the planetary A index (Ap).

The Space Weather page presents these indices in a visually engaging way:


Main Graph: A continuously updated graph displays the Kyoto Dst, proton flux, andTromso A-index values for the running year. Users can filter these data for specific time
periods, ranging from 1 day to 9 months. The graph is fully interactive, allowing users tozoom in, pan, and save the display.
Long-Term Forecast: This graph presents 27-day forecasts for solar flux, planetary A
index, and the highest planetary K index, provided by NOAA.
Short-Term Forecast: A 3-day forecast for the planetary K index, also provided by NOAA,
is presented for closer observation of short-term geomagnetic activity.

37

By monitoring these indices, you can gain a better understanding of how solar disturbances inspace weather can affect HF communication. This knowledge is crucial as VOACAP propagation
predictions are based on the assumption of quiet geomagnetic activity.

16. Discover Earth-Moon-Earth (EME) Times
Planning your next EME QSO just got easier! We provide a powerful tool to determine common
moon window times for any two locations on Earth for the following seven-day period.
How to Find Your EME Window:
1. Set Your Locations: Place the TX and RX markers on the map at your desired transmitterand receiver coordinates.
2. Choose Your Date: Select the starting date for your EME window calculations using thecalendar in the bottom-left corner.
3. Activate EME Analysis: Click the green EME button below the map.
VOACAP Online does the rest:Calculates Moon Visibility: The system determines moon rise, solar noon, and set times
for both locations over a seven-day period.
Identifies Common Windows: It pinpoints the overlapping time periods when the moonis visible at both locations simultaneously.
Provides Detailed Data: Within each common window, you'll find calculations for moonelevation, azimuth, and distance at 5-minute intervals. Results are displayed side-by-side
for easy comparison.

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