VOACAP Online Point-to-Point User Interface revamped

It happened last night: the familiar 24-hour circular prediction chart was replaced by versatile and detailed propagation prediction charts, 15 charts to be exact, on the front page of the VOACAP Online P2P predictions. URL: http://www.voacap.com/p2p/index.html

The reason is simple: the new charts contribute to better assessment of HF propagation. You can paint the big picture with a single VOACAP output parameter but, for a more accurate picture, you will need (at least) three: REL (used by the earlier 24-hour circular chart which is still available via a separate link: http://www.voacap.com/p2p/index2.html) but also SDBW (signal power) and MUFday. These are now offered to the ham community, in addition to band-by-band predictions, which even visualize the signal power distribution (upper decile, median and lower decile).

Each chart offers multi-colored lines for the various parameters. And thanks to the JavaScript framework (plotly.js) used for plotting these graphs, all visible legend parameters/frequencies can all be toggled on and off by clicking on the legend values on the bottom of the graphs, helping the user focus on relevant parameters/frequencies only. Also there is a versatile toolbox on the top-right corner of each graph that allows the user to save the graph as PNG, zoom in/out, compare results data on all frequencies on mouse hover, pan the chart, and more.

CLICK TO ENLARGE THE IMAGE

But let's now make a recap of what the three parameters -- REL, SDBW and MUFday -- mean to you.

The REL or Circuit Reliability. The REL is related to VOACAP's output parameters of SNR (Signal-to-Noise Ratio) and REQ.SNR (Required Signal-to-Noise Ratio), and is defined as a circuit reliability factor. It tells us the percentage of days in the month when the SNR value (which is not shown in the charts as a separate parameter) will equal to or exceed the REQ.SNR. The REQ.SNR is an internal value set by me, related to the transmitting mode selected. For CW, the REQ.SNR is set to 24 (dB-Hz), and for SSB, it's 38 dB-Hz.

SDBW or Signal Power. The SDBW indicates the dBW (the strength of a signal expressed in decibels relative to one watt) value (the green line in the chart) that can be maintained on 50% of the days (ie. on 15 days) in the month. In a similar fashion, the SDBW90 indicates the dBW or signal strength value that can be maintained on 90% of the days (ie. on 27 days) in the month. And finally, the SDBW10 is the dbW value that can be maintained on 10% of the days (ie. on 3 days) in the month. However, it does not tell us which days are good or which days are bad. The SDBW10 and SDBW90 values are the top and bottom boundaries (respectively) of the light-gray area that is now always visible in all band-by-band prediction charts. The signal power distribution is calculated for Short-Path circuits only. The SDBW values are all translated to corresponding S-Meter readings in the charts.

• Read more: Beware of extremely wide Signal Power distributions 

The MUFday will tell us what percentage of the days in a month at that hour will be below the predicted MUF (Median Maximum Usable Frequency) for the most reliable mode (MRM). The MRM is the mode with the highest reliability of meeting the Required Signal-to-Noise Ratio, or REQ.SNR (see above).

These three output parameters are being calculated via Short-Path and Long-Path.

At the same time, I changed the default setting for the Transmit & Receive Antenna and Transmit Power. Now the TX & RX antenna is a quarter-wave vertical antenna over a good ground, and the TX power is set to 1.5 kW.

So, how to use the new charts? I regularly follow this sequence:

1. Check the bands of the best REL values for the path in question.
2. Then check the SDBW values for the best bands.
3. When you have your candidate bands selected, then go to the charts for those bands.
4. In band-by-band charts, pay attention to MUFday values, and the signal power (SDBW) distribution (the light gray area). If the distribution is extremely wide, there is a chance that VOACAP unfortunately does not have a good idea of what's going on.
5. Be sure to check the Long-Path predictions, too! On long-haul paths, Long-Path may bring nice surprises.

SDBW, SDBW10 and SDBW90: The Predicted Signal Power Distribution

During the past few days, two more Signal Power parameters - namely, SDBW10 and SDBW90 - were added to the VOACAP D-I-Y Charts and the similar charts at VOACAP Online Point-to-Point service. As a result, these values are being used to create an area filled with the light-gray color, showing the Signal Power distribution. It's calculated for Short-Path circuits only.

The Signal Power distribution tells us what levels of signal power at the receiver are to be expected over the days in the month on the given frequency at the given hour.

The SDBW indicates the dBW (the strength of a signal expressed in decibels relative to one watt) value (the green line in the chart) that can be maintained on 50% of the days (ie. on 15 days) in the month. In a similar fashion, the SDBW90 indicates the dBW or signal strength value that can be maintained on 90% of the days (ie. on 27 days) in the month. And finally, the SDBW10 is the dbW value that can be maintained on 10% of the days (ie. on 3 days) in the month. However, it does not tell us which days are good or which days are bad. The SDBW10 and SDBW90 values are the top and bottom boundaries (respectively) of the light-gray area that is now always visible in all band-by-band prediction charts.

In our charts, we also display the REL and MUFday values in order to get as complete a picture as possible for the final propagation assessment. The REL is related to VOACAP's output parameters of SNR (Signal-to-Noise Ratio) and REQ.SNR (Required Signal-to-Noise Ratio), and is defined as a circuit reliability factor. It tells us the percentage of days in the month when the SNR value (which is not shown in the charts as a separate parameter) will equal to or exceed the REQ.SNR. The REQ.SNR is an internal value related to the TX mode selected. For CW, the REQ.SNR is set to 24 (dB-Hz), and for SSB, it's 38 dB-Hz. And, last but not the least, the MUFday values will tell us what percentage of the days in a month will be below the predicted MUF (Maximum Usable Frequency). These values will be calculated via Short-Path and Long-Path.

Beware of extremely wide Signal Power distributions

Whenever you see that a Signal Power distribution is extremely wide, e.g. ranging from the S-Meter reading of S0 to S8 at any given hour, you are getting into the noise of the program, meaning that VOACAP will give predictions even when it has no idea what is going to happen. If we believe the prediction, then VOACAP is saying that 80% of the days of the month (bounded by SDBW90 and SDBW10) will have a Signal Power somewhere between S0 and S8. That is a spread of 48 dB! If the program could talk, it would tell you that it doesn't have a really good idea what is going to happen on that frequency at that hour.

The area filled with light-gray (= Short-Path Signal Power distribution) is bounded by the SDBW10 (top) and SDBW90 (bottom) values. Times and frequencies with extremely wide Signal Power distributions are not reliable enough. Typically, in such cases, the MUFday values are also low.

DIY VOACAP HF Propagation Predictions for DXpeditions

I am happy to announce that VOACAP Online has now an option to offer do-it-yourself HF propagation predictions, suitable for the websites of DXpeditions (and for other needs, too).

If you wish to embed the propagation prediction component in your pages, just use the following code:

NOTE: the code is one big line, no linebreaks as in this example!

CLICK IMAGE TO ENLARGE!

where:

CALLSIGN (parameter "c") = the callsign of the DXpedition (the Transmitter site)
TXLOCATOR (parameter "l", like Lima) = the Maidenhead Grid Locator for the Transmitter site. To find your grid locator, please see: www.voacap.com/qth.html
YEAR (parameter "y") = the year the DXpedition is taking place, e.g. 2017
MONTH-NUMBER (parameter "m") = the number of month when the DXpedition is taking place, e.g. for July, MONTH-NUMBER is 7.
TXPOWER (parameter "p") = the transmitting power in kilowatts, e.g. 1.5
MODE (parameter "me") = either CW or SSB. If you will use both, set this parameter to CW.

So, when all the components are in place, the complete code might look like this (the example below is for the Bouvet DXpedition in February 2018):

NOTE: the code is one big line, no linebreaks as in this example!

CLICK IMAGE TO ENLARGE!

The layout on your page will be something like this (enter your grid locator in the field, press "Run", and see the results!):

The graphical predictions will be similar to this:

Overview of the prediction in terms of Reliability (REL), Signal Strength (S DBW) and MUFday, followed by band-specific predictions, from 80 Meters to 10 Meters, Short-Path (SP) and Long-Path (LP). The charts are all interactive as you hover the mouse over them.

The service is offered to the ham community free-of-charge. If you are using this component as part of your webpages, I would like to hear from you!

Versatile charts for Reliability, Signal Power and MUFday available at VOACAP Online P2P

I am happy to report that another way of visualizing three critical output parameters for HF propagation predictions at the VOACAP Online Point-to-point service is now available. These charts, namely Reliability (REL), Signal Power (S DBW) and MUFday, can be viewed at www.voacap.com/p2p/index.html by clicking on the "Tri-graph" button.

Each chart offers multi-colored line graphs for all frequencies from 80 meters to 10 meters. And thanks to the JavaScript framework (plotly.js) used for plotting these graphs, they can all be toggled on and off by clicking on the legend values on the right, which helps the user focus on relevant graphs only. Also there are versatile tools that allow you to save the graph as PNG, zoom in/out, compare results data on all frequencies on mouse hover, pan the chart, and more.

The REL and MUFday data is presented as percentages from 0 to 100 (%) whereas the Signal Power (S DBW) data is shown as dBW values from -163 to -103. The value of -163 is an extremely low noise value of my own choosing, and the next value of -157 represents a median S-meter reading of S0. The value of -103 corresponds to a median S-meter reading of S9. The steps are 6 dB or one S-meter reading step.

On the Signal Power graph, the Y-axis values span from -163 dBW (noise level) to -103 dBW (S-meter reading of S9).

The toolbox with many useful functions such as saving the graph as PNG (far left).

Hope you enjoy the new charts!

Adding MUFday to the equation

I have been further re-factoring the code that produces the VOACAP HF propagation prediction in table format. Such tables are available e.g. on the VOACAP Point-to-Point page (www.voacap.com/p2p/index.html > All-year prediction) and on VOACAP DX Charts (www.voacap.com/dx.html) or on VOACAP Propagation Planner (www.voacap.com/planner.html). The re-factored code has made it possible for me to add the MUFday parameter to the predictions. And it's a great enhancement, making the high-band predictions even more realistic. Be warned that the 24-hour prediction wheel I use on the VOACAP P2P front page is now "out-of-date" on Above-the-MUF frequencies!

So, with the introduction of MUFday in all assessments, there will be more gray cells in the prediction tables from now on. 

On lower frequencies, the color of gray does not indicate any probability value, in contrast to all other colors used. Instead, gray shows that, although VOACAP does not predict any probability for that specific hour (R=0% in the popup window), some signal power (S in the pop-up window) has been predicted which may translate into workable conditions. So, in a sense, gray indicates "a gray area" where QSOs may be possible.

On higher frequencies, typically on Above-the-MUF frequencies, the color of gray is a sign of extremely poor probabilities. These are actually cases where VOACAP predicts positive REL values but unfortunately VOACAP does not know what's really happening up there. If you take a closer look at the values reported in the pop-up window over the cell (the R, S and M values), the S (Signal Power) value can be very low (e.g. -164 and below which means that there is hardly any signal in the noise).

Frankly, I should have implemented the MUFday assessment much earlier. Let me explain the nature of MUFday as concretely as possible. The value of the MUFday is the fraction of the days in a month at that hour that the operating frequency is below the MUF for the most reliable mode (that is, the mode with the highest reliability of meeting the required Signal-to-Noise Ratio, or SNR). So, on higher frequencies, I have now set the threshold to 10% for MUFday in my assessments. This means that if the MUFday value is less than 10% (or less than 3 days), then the frequency hour cell will be colored gray. And it's totally ok, as this actually means that for more than 90% of the days in a month, QSOs are likely not to happen. The odds are pretty poor.

At 12 UTC on 10 Meters in February 2018 (from OH6 to 3Y0Z), VOACAP says that the REL (R or the probability for a QSO) is a good 21%! However, the Signal Power (S) is -173, way down in the noise. And what is more, the MUFday (M) is a mere 5%. So, the verdict is that there is only the slightest chance (frankly, if any) that QSOs can happen on 10 Meters with the power and antenna chosen. Therefore, the cell is rightfully colored as gray.

Recapping the R, S and M values

As you know, all table charts are interactive: if you hover your mouse over table cells, you will see a pop-up text, now showing three parameter values: R, S and M.

The R is VOACAP's REL or QSO probability in percentages, and the S is VOACAP's S DBW or Signal Power value in dBW. For instance, the signal power value of -164 can be considered to be on the verge of the noise in remote, extremely low-noise locations whereas the S DBW value of -93 corresponds to S9 on the S meter. Read more about translating the signal power values (S DBW) into S-meter values here: http://www.voacap.com/s-meter.html.

And finally, the new M parameter is VOACAP's MUFday value in percentages, indicating the probability for the operating frequency on that hour being BELOW the median MUF calculated.

All in all, MUFday is a much-anticipated parameter to give the wild REL values on Above-the-MUF frequencies a more realistic interpretation.