One of the most common question I hear from Shortwave radio Listers (SWLers), is, "When will good propagation occur?" While noise is always a factor limiting what you can hear, noise is only one aspect of HF reception. The varying ionosphere makes even powerful broadcast signals come and go, and it's hard to know what to expect when you settle down for an evening of shortwave listening. Of course, you can always tune to the frequency where you last heard a favorite station, but if there is noise yet no radio signal, what then? It's frustrating to just listen in the blind.

ACE-HF is a powerful tool that you can add to your SWLing operations. The latest version of ACE-HF System Simulation and Visualization Software is version 2.05. This version is specifically designed for shortwave listeners as well as for Amateur Radio Operators.

Sometimes called "the Cadillac of HF Propagation Programs", ACE-HF is derived from the professional ACE-HF NETWORK software for government and commercial HF network operators, used to simulate networks run by military and other groups. "ACE" stands for Animated Communications Effectiveness, the copyrighted technique for displaying both transmission and reception coverage on maps of the world. This key feature yields great insight into the coverage achieved by any HF station, but is especially helpful to see whether a particular broadcaster covers your listening post. You can also simulate a point-to-point circuit from any world location to your station and show the predictions graphically (useful, say, if you are planning an emergency support radio net, or a health and welfare traffic net). All ACE-HF charts may be animated-one of the hottest features of ACE-HF.

The new ACE-HF is designed for shortwave listening enthusiasts-those who are intrigued by the methods used by HF International Broadcasters and who would like to optimize their HF listening experience. I am certainly an enthusiast (see my Shortwave Listening Resource Center), so to investigate the new ACE-HF I began by simulating a shortwave circuit from the well-known WCR (Worldwide Christian Radio) station in Nashville, Tennessee. Just for fun, I pretended I was a wandering oil company worker stationed in Riyadh, Saudi Arabia, hoping to hear something from state-side.



I began my review session with the intuitive ACE-HF inputs screen shown above and used some of the new features for shortwave listeners. There is a new HFCC (High Frequency Co-ordination Conference) database of over 640 International Broadcast transmit sites that has a new sorting feature, so I was able to quickly select the WCR station. I set WCR's transmit power at 100,000 watts and selected the CONST17.VOA antenna from the more than 660 HFCC antenna models now included in ACE-HF. This general purpose 17-dBi, omni-directional antenna is recommended by the Voice of America, but I could have selected another one of the HFCC models that include curtain arrays with up to 30-dBi gain. I assumed the SWWHIP.VOA antenna for my receiver. And I selected the AM service type, although I could have chosen the new IB service type for commercial quality HF reception.

The ACE-HF design assumes that the user employs International Broadcasting schedules as posted on the Internet (see my resource at HFRadio.org's SWBC page, and other schedules posted at the HFRadio.org SWLing Resource Center), where details such as transmit power, azimuth (main beam) angles, frequencies and time schedules are readily available.

All these adjustments take more time to read about than to set up, so I just clicked on Run Circuit Predictions to see the prediction charts for my circuit. I always look first at the SNR Summary Chart:



It wasn't surprising to see that this long circuit of nearly 12,000 km favored the higher frequencies. This was confirmed by the MUF (Maximum Usable Frequency) Chart, which showed a median MUF of about 16 MHz at the current time-of-day (about 2100 UTC):



Finally, the SNR chart for WCR's 15.82 MHz frequency predicted good connectivity at the current time:



Already, I was ahead of the game. I could now tune to 15.82 MHz with confidence, and the program should be heard loud and clear at my Riyadh listening post!

Area Coverage Predictions

Now my curiosity was aroused. Could I hear the WCR station from other locations? To answer this question, I created a series of worldwide area coverage predictions from the WCR transmitter at 10 frequencies and for 24 hours. (It only took a couple of minutes.) Now, I could see coverage at any world location and animate it by time. I selected the predictions for 15.82 MHz and started the animation (which will advance by one hour every hour, or can be run quickly like a movie). Wow! Suddenly the insight came flooding in as the variables of HF propagation became evident. No wonder WCR could only be heard at some times-of-day. Here's just one snapshot of the area covered from Nashville at 2100 UTC and at 15.82 MHz:



Another handy technique is to animate the area display as a function of frequency. Just select a given hour-in my review I picked 2100 UTC-and Select All Freqs. Now you can see just which HF bands can be heard as far away as Riyadh, or anywhere else for that matter. I can see that using these techniques and tools along with a closer look at the schedules of International Broadcasters is a powerful way to hunt down stations I've hoped to hear but never seemed to be tuned to at the right time at the best frequency.

CIRAF Zones

International Broadcasting schedules show the target CIRAF zones to be covered by each scheduled transmission. CIRAF stands for Conferencia Internacional de Radiodifusión por Altas Frecuencias and was a conference first held in Mexico City in the 1940s to define areas to be served by each shortwave broadcaster. Continuing HFCC meetings are held to refine such agreements. Each CIRAF target zone has a number, and the Internet schedules list those numbers. For example, in last winter's HFCC schedule for WCR's broadcast at 15.82 MHz, CIRAF zones 4, 9, 27, 28, and 37-39 are to be targeted between the hours of 1100 to 2200 UTC, and the station's antenna azimuth setting for those zones is 46°. Our circuit to Riyadh was on an azimuth of 43°, so we should be in good shape.

ACE-HF shows CIRAF zones on area coverage world maps, as shown below. Just click the CIRAF Target Zones switch to show the zones and their numbers. Saudi Arabia is in Zone 39.



Who else could I hear from my Riyadh location? ACE-HF can make Reception Area displays to show areas covered from your location, and an example is shown below. This figure shows 15.82 MHz at 2100 UTC, but the display can be animated over a range of frequencies or times-of-day. Since the receive location was fixed, the software, in its complex scientific number crunching, effectively moves the transmitter all over the world to create a display of reception coverage. In my review using an average up-to-date computer with 1.8 GHz processing speed, I ran 61 by 61 points, times 10 frequencies, times 24 hours. That equals 893,040 equivalent point-to-point circuit predictions, which only took a little over 2 minutes to complete.



Antenna Analysis

Antenna gains and patterns are always critical in HF communications, whether the system is for Ham radio or international broadcasting on shortwave. ACE-HF now includes a great new capability for showing the effectiveness of HF antennas, and an example chart is as follows:



In this example, I selected a horizontal dipole array antenna that has 4 elements per row and 4 elements per stack, a typical curtain array. The antenna's design point is 7 MHz, and the chart shows the vertical gain pattern at that frequency, with a directivity gain of 22.1 dBi at the main lobe. The chart also shows the calculated range of elevation angles for the WCR-Riyadh circuit-the green line-indicating that this antenna is a good match for the propagation modes of this DX circuit.

Circuit Group Calculations

ACE-HF also has a special chart showing the predicted integrity of as many as 18 circuits. In Ham operation, the chart is a great aid during contest activity as one can easily see when the bands are open at the current time to different target areas. By advancing the chart to a future time, it is a great aid during contest planning.

The same chart may be used for predicting reception from as many as 18 of your favorite shortwave radio stations. Again using the international broadcasting example, I defined circuits from 18 stations to Riyadh, using the generic CONST17.VOA antennas and specifying uniform transmit powers of 100,000 watts (but actual powers could have been taken from the HFCC schedule). Results for a time of 0600 UTC are shown below. I used the WCR frequencies, but average frequencies in the various bands could have been specified instead. The group chart shows that reception from WCR is fading at Riyadh as daylight approaches the path midpoint (as was seen above), but European stations can still be heard, and reception from nearby stations is strong.



This chart is a great tool for the shortwave listener, and will quickly become a favorite to watch during your day of radio monitoring. The chart appears for the current time and automatically advances every hour, showing when different circuits are most likely to be heard-when the SNR (Signal-to-Noise Ratio) predictions of the table are "in the green". (The blue cells indicate best frequencies.) You can construct an unlimited number of such group charts for various scenarios, and can save and recall them for future listening.

ACE-HF V2.05 is highly recommended for both Hams and SWL enthusiasts.

ORDERING DETAILS

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