David Treharne N8HKU Ford Amateur Radio League March 9, 2017 VOACAP Presentation David Treharne N8HKU Ford Amateur Radio League March 9, 2017

What is VOACAP VOACAP: Voice of America Coverage Analysis Program. VOACAP is an improved and corrected version of IONCAP, (Ionospheric Communications Analysis and Prediction Program) retaining all of the theory as put forth by John Lloyd, George Haydon, Donald Lucas and Larry Teters in the 1975- 1985 time-frame with modifications which were suggested/approved by George Lane, Donald Lucas, George Haydon and A. D. Spaulding (a world authority on HF radio noise predictions). VOACAP is the result of 50+ years of U.S. HF research and development Considered by many as the most professional HF system performance prediction tool available on the market Used currently for HF frequency planning by Voice of America and a number of other international HF broadcasters and institutions all over the world. Easy to use graphical user interface and, for advanced users, powerful command line options

Long History!

Where does the prediction come from? Started way back when HF was beginning to be used in the 1930’s! Uses statistical and empirical calculations based on decades of ionospheric research into the F2 layer as well as the absorption properties of the D layer. Takes into account the month and day of the year to reflect seasonal variations in propagation. Ioncap developed its statistical properties from data taken beteween 1958 and 1963. VOACAP improved on these by using VOA listener reports over the years under a variety of solar and geomagnetic conditions VOACAP uses smoothed sunspot cycles, but not planetary indices. Therefore, it does not predict coverage during active solar storms. The use of the Smoothed Sunspot numbers does give it good statistical correlation overall, and we know that the ionosphere does not react immediately to the current sunspot value, but it ebbs and flows with the averages. VOACAP calculates the signal to noise ratio as part of its measurements. It predicts communication potential in CW, RTTY, and SSB modes, as requested by the user. VOACAP is best at 1 to 3 skips. The estimate for each subsequent skip contains errors as the bounce from the earth back to the sky is not as precise as the take off angle calculations from the original antenna model. So, an 40m or 80m signal to Australia may not be as accurate as a 10m or 15m prediction!

VOACAP Online Prediction tool For this presentation, will discuss: The Coverage Area maps The Point to Point Predictions www.voacap.com All of these tools are available online, with no programs to download. The online programs automatically handle the sunspot prediction as well.

Sunspot Cycle

VOACAP Accuracy How do we establish how good the program does? How about comparing it to actual contest results? The program allows us to backcast data from the past One advantage in backcasting: it uses the actual smoothed sunspot number (37) instead of the actual sunspot number of late June. And, it is only using June as a basis, not the 4th weekend in June. But, we will use it anyway! Use the 2016 LARC-FARL Field Day The LARC-1 radio was primarily on 40m. Let’s take a look at how the station did! Using the dipole antenna at 15m altitude for the transmit antenna, close to the G5RV Jr antenna and height Using a dipole antenna at 10m for the receive side, representing the Field Day receivers Noise level: quiet: Very generous for Field Day, but I left it as the baseline

1800 Hr contest start This is how it looks initially. We will zoom in on North America to find the probable reception versus actual

1800 Hr Field Day 40M PA What do we see? Pennsylvania and NC are the highest number of contacts, in the higher probability zone. Not much in Illinois and Indiana and OH, which are predicted high Al, VT are in the lower probability band No one in the 10% or less band: Decent prediction! QC ON MN VT NY DE WI MI PA OH NJ IA IL IN WV KY VA MD IN NC GA AL

Prediction Movement on 40m through the afternoon Prediction Movement on 40m through the afternoon. New States picked up over the hours 1800 UTC (2pm) 1900 UTC (3pm) 2000 UTC (4pm) 2100 UTC (5pm) 2200 UTC (6pm) States added AL, DE, GA, IA, ID, IL, IN, KY, MD, MI, MN, NC, NJ, OH, ON, PA, QC, TN, VA, VT, WI, WV States added CT MA MO SC States added AR NH SD States added MA ND States added KS

Not as many new stations as the map suggests, So, I changed the prediction to the receive antenna. ¼ wave vertical, (-140dB noise floor) 0400 UTC (12am) 0500 UTC (1am) 0600 UTC (2am) 0900 UTC (5am) 1000 UTC (6am) 10m high Dipole, Quiet noise floor States added -- States added -- States added CA CO States added TX States added AZ ¼ Wave Vertical, noisy noise floor Predictions better with the noise and antenna change, as CO, CA, TX, and AZ were single stations

What went on? There are a limited number of Field Day sites on the air at any given time. Duplicates are not counted, and many never try to call a 2nd time. Other stations are not on 40m all of the time, they would have been on other bands The noise floor was not quiet. There was a lot of manmade congestion (QRM) on the band. The prediction indicated the contacts should have stretched The station was on 40m the whole day and night 0623 was the last contact until 0845, then 0940. After 1000, and especially after 1100, contacts were up for the rest of the contest, all single skip Midwest to East Coast contacts.

Point to Point predictions Useful for trying to connect with the rare DX or rare state contact. The user chooses where they want to work, what mode they want to use, the antenna being used, and then runs the program to determine the best bands and times to work that station System outputs probabilities by band for the 24 hour period. Example: Look for the path from MI to Alaska on last Field Day

2016 Field Day Section Coverage 76 out of 80 sections worked Not Worked: Alaska Wyoming Newfoundland Northwest Territories Single Contact: Alberta East Bay (California) Manitoba Hawaii West Texas DX: Bahamas, Belize, Jamaica, Scotland

MI to Alaska Prediction SSB MI to Alaska Prediction Best bands were no more likely than 50% chance in SSB, but a 70% to 80% chance on CW SSB: best chance: 0100 (9pm Saturday) to 0400 (12am Sunday) hours on 20M Next best was 30m from 0300 to 1200 UTC, but that is not a band for the event. We did not make contact with Alaska on Field Day. Did we have a station on 20m from 9pm to 12am Sunday morning? No, we had SSB1 on 20m from 1800 through 2300 hours, 10% to 30% chance of contacting. CW was on 20m from 22:27 through 00:14. They had a chance at 2300 to 0000 hours, but did not make a contact. We had both SSB and CW stations on 40m and 80m through 1100 Sunday morning, when SSB1 went on 20m. Under a 30% chance of making a contact right at the end of the contest. CW

How About where we made a Single Contact? How lucky were we? CW, Michigan to Honolulu. Best chance 70% to 80%: 20M: 0200 to 0500, Moderate chance 60%: 0000 to 0200 on 20m Answer:

How About West Texas? Only one contact there! CW, Michigan to West Texas. Best chance 20M from the start of the contest at 1800 hours through 0300 on 20m, then 1200 though 1800 on 20m. 2nd best chance 40M from 0000 hours through 1200 hours Answer: The actual contact was mde within the high probability band. Why only a single contact? Why do we only get a single contact with some areas, and a tremendous number of contacts from others? The prediction tool thinks it should have! See the propagation map.

Conclusions The VOACAP prediction tool did reasonably well for the Field Day contest, but it has its limitations Does not account for the direction of the antenna Does not account for geomagnetic storms Uses the SSN, which may not represent any particular day Not great if you have more than 3 hops, like trying to work Australia on 40m. It does have a good probability tool, especially if you need to work that “rare one”. It would be a good tool to have to try and pick up the perennial difficult stations to contact, like NWT, Alaska, Newfoundland, Hawaii. We could try to schedule a station to work that mode during the peak probability times and try and snag the rare ones. (Very good for the November Sweepstakes, when you are in a contest to find the rare stations.) The programs are pretty good at defining the coverage for a station with a given antenna. I would like to look at other Field Day bands, such as 20m, to see how the prediction worked there.

Bibliography http://www.voacap.com/p2p/index.html http://www.voacap.com/area/index.html http://www.voacap.com/ http://www.swpc.noaa.gov/products/solar-cycle-progression http://www.astrosurf.com/luxorion/qsl-soft-voacap.htm