VOACAP Predictions for WRTC 2018

by Jari Perkiömäki, OH6BG/OG6G

Introduction

I am privileged and honored to be able to contribute to this remarkable WRTC event by offering a starter set of propagation tools and analysis. Unfortunately, the files you can view and download here cannot fully convey the interactive nature of some of the predictions (the prediction tables in particular) where you will have to consider several parameters at once. For a serious enthusiast, it's best to run and study the results online at http://voacap.com/hf. That being said, I hope the tools and files offered here will give you a good start.
THE PREDICTION SETTINGS

Date: July 14-15, 2018
Grid: JO61LS (TX site)
Powr: 100 watts
Mode: CW (19 dB-Hz)

TX ANTENNAS USED

80-40M: Dipole @ 10M (33ft)
20-10M: 2-el Yagi @ 10M (33ft)

RX ANTENNAS USED

80-40M: 1/4 wl Vertical with Good Ground
20-10M: 3-el Yagi @ 15M (50ft)

MISCELLANEOUS

Noise: Quiet
SSN: 5 (July)
Method: 30
Min TOA: 3 degrees

Follow the Golden Rule

The golden rule for building the big picture is to not rely on one VOACAP output parameter only. In other words, using the median Signal Power (S DBW), or Reliability (REL), or any other single parameter as your only guide may not be as productive as studying multiple parameters in parallel, and understanding their total impact. Unfortunately, I cannot go into details here, but let me just refer to a few links which may help you understand the predictions better:

Start with the Sun

Everything starts with the Sun, and this is especially true when you e.g. assess the predictions for low bands. For example, simulating the way how the grayline terminator moves over time, in search for the best times on these bands, cannot be adequately visualized here. Nevertheless, it's important for you to do these simulations (e.g. at http://voacap.com/hf) in order to complement the predictions produced by VOACAP as the software does not take the effects/enhancements of sunrise and sunset properly into account.

So, the starting point is to know the relevant sunrise and sunset times, and then use the grayline terminator simulation to see how the things look like at the times you regard as relevant for your target areas.

Furthermore, in July, the occurrence of the sporadic E is more than likely. In general, this can be hard for propagation prediction software to tackle. Nevertheless, I have run the analysis with the E layer option set to on. In VOACAP, when you do that, it means that the E layer is strongly present everywhere globally (which it is not in real life), not just in a particular region. I hope this will help determine in which direction to look if sporadic E conditions are present at that time.

Monitor the Space Weather

As we all know, VOACAP cannot predict day-to-day (not to talk about near-real-time) propagation conditions. Instead, the software uses a statistical model to provide a statistical assessment of what it thinks will happen on a particular band at a particular time over the 30 days in a month under undisturbed conditions. Therefore, it's essential to monitor how the current space weather looks like and how it's expected to develop. Knowing the generic space weather conditions, we may then hopefully be in a position to interpolate the specific propagation predictions according to daily conditions. However, even disturbed conditions may produce unexpected, unpredictable results!

Please note that space weather parameters such as the A index, or SFI, or sunspot numbers, and so forth, will reveal nothing about the propagation of signals from one specific QTH to another. These values just reflect how "the bigger framework", i.e. the ionosphere, may behave in general.

To help you monitor the relevant space weather parameters, please see the special space weather page link below. In particular, pay attention to the development of the Kyoto Dst (Disturbance Storm Time) value. High peaks above zero often mean enhanced conditions; deep drops below zero mean disturbed conditions. As you can see, there is a relation to the Tromsø, Norway (polar cap) A index. I personally follow Kyoto Dst closely; perhaps you swear by the K and A indices :)

Leverage the Predictions

The point-to-point (zone) predictions were run from the WRTC 2018 Maidenhead Grid locator of JO61LS to the extended sets of CQ Zones and ITU Zones to provide a better geographical coverage in terms of DXCC countries and locations.

The coverage area maps have been plotted with the REL and SDBW parameter outputs. 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 broadly defined as a circuit reliability factor. It tells us the percentage of the days in a month when the SNR value 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 19 (dB-Hz). The SDBW maps plot the dBW (the strength of a signal expressed in decibels relative to one watt) value that can be maintained on 50% of the days (ie. on 15 days) in the month. These are the maps to study on low-bands in particular! Read more about translating the signal power values into S-meter values here: http://www.voacap.com/s-meter.html.

All times are UTC, and all VOACAP predictions span 60 minutes but not necessarily the way you may think. A prediction for 01 UTC does not span from 01:00 to 02:00 but, in fact, from 00:30 to 01:30 UTC!

All predictions were run with the E layer set to ON (to tackle the sporadic E) and OFF. Furthermore, these predictions are via Short-Path only. Please do study the corresponding Long-Path predictions e.g. at http://voacap.com/hf, by placing the RX (blue) marker over your primary target areas on the map and clicking the "Band-by-band Prediction" or "Planner" button.

Last but not the least, the prediction tables use the following color scheme from white (worst) to red (best):

The color of gray does not indicate any probability value. Instead, it shows especially on the low bands that, although VOACAP does not predict any probability for that specific hour, some signal power has been predicted which may translate into workable conditions. So, in a sense, gray indicates a heads-up note -- "a gray area" where QSOs may (or may not) be possible.

Propagation by Band

Without the E layer:

80 Meters: CQ Zones, ITU Zones
40 Meters: CQ Zones, ITU Zones
20 Meters: CQ Zones, ITU Zones
15 Meters: CQ Zones, ITU Zones
10 Meters: CQ Zones, ITU Zones

With the E layer:

80 Meters: CQ Zones, ITU Zones
40 Meters: CQ Zones, ITU Zones
20 Meters: CQ Zones, ITU Zones
15 Meters: CQ Zones, ITU Zones
10 Meters: CQ Zones, ITU Zones

Propagation by Zone

CQ Zones:  without the E layer, with the E layer
ITU Zones: without the E layer, with the E layer

Coverage Area Maps: Reliability (REL)

Without the E layer:

80 Meters: 00-11 UTC, 12-23 UTC
40 Meters: 00-11 UTC, 12-23 UTC
20 Meters: 00-11 UTC, 12-23 UTC
15 Meters: 00-11 UTC, 12-23 UTC
10 Meters: 00-11 UTC, 12-23 UTC

With the E layer:

80 Meters: 00-11 UTC, 12-23 UTC
40 Meters: 00-11 UTC, 12-23 UTC
20 Meters: 00-11 UTC, 12-23 UTC
15 Meters: 00-11 UTC, 12-23 UTC
10 Meters: 00-11 UTC, 12-23 UTC

Coverage Area Maps: Median Signal Power (S DBW)

Without the E layer:

80 Meters: 00-11 UTC, 12-23 UTC
40 Meters: 00-11 UTC, 12-23 UTC
20 Meters: 00-11 UTC, 12-23 UTC
15 Meters: 00-11 UTC, 12-23 UTC
10 Meters: 00-11 UTC, 12-23 UTC

With the E layer:

80 Meters: 00-11 UTC, 12-23 UTC
40 Meters: 00-11 UTC, 12-23 UTC
20 Meters: 00-11 UTC, 12-23 UTC
15 Meters: 00-11 UTC, 12-23 UTC
10 Meters: 00-11 UTC, 12-23 UTC

Disclaimer: Any software or service on this website is provided "as is". Use at your own risk.


© 2003-2018 Jari Perkiömäki OH6BG/OG6G. SSN source for all VOACAP Online services: WDC-SILSO, Royal Observatory of Belgium, Brussels.