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

2. 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 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

3. Long History!

4. 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!

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

6. Sunspot Cycle

7. 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

8. 1800 Hr contest start
This is how it looks initially. We will zoom in on North America to find the probable reception versus actual

9. 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

10. 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

11. 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

12. 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.

13. 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

14. 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

15. 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 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

16. 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:

17. 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.

18. 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.

19. Bibliography http://www.voacap.com/p2p/index.html