A 5-Year 10-Meter Es Propagation Study Using PropNET - Final Part

Questions and Answers:
“Is Es propagation truly a seasonal occurrence?”
The answer derived from this study is definitely yes. The season begins within days of April 25 and progressively increases up to May 6, at which time it is in full swing and remains totally active until at least August 15. There is still a good chance that activity continues till the end of August. From the study, the season begins 8 weeks prior to the Summer Solstice and ends around 10 weeks after it.

“Since it has been determined to be seasonal, is activity evenly distributed around the Summer Solstice?”
After three years, I thought it was not. But now after 5 years I believe it is. The best part of the Es season is concentrated in the first half (8 weeks long) in a 4-week segment and one should make as much effort as one can during that period. Es are great from the 3rd week through the 6th week (May 9 – June 5). It might calm down slightly for the next four weeks around the solstice, but it in no way does it mean that the season is over. It is still very active during that lull. Once we arrive at Independence Day (July 4th), the season picks up again and it is not until around August 1 that a real decline is noticed. The season does not actually end until sometimes between August 15 and September 1. Statistically and graphically it has a slight right-skewed distribution of opportunities, still the median points of captures and opportunities rested near the Summer Solstice.

“It appears that one works most of their QSOs during the afternoon and evening hours. Is this the best time to work Es?”
No it is not. It appears this way only because most Hams are active late in the afternoon and evenings. The absolute best hours are from after sunrise till the actual Solar Noon hour. On weekends and days off from work, make every effort during the season to work Es during these hours. The late afternoon hours are also very good, distances covered are also better, but opportunities decline once the sun has set. Es are mostly diurnal (daytime phenomena). Es do occur in the late evening and early morning hours. When they do, it is a very special event. Enjoy it and make use of the opening.

“Do Es favor specific directions at certain times?”
Yes it does, and it has to do with the location of the sun. It appears that you follow the sun in order to apply where it is best. As the sun rises, the best conditions tend to be towards the North and East. Gradually, as the sun is high over the horizon, southern paths improve. Once the sun has moved beyond Solar Noon, western paths become better than eastern ones. Therefore, the tendency is that openings appear in the east and north first and then will develop towards the south and the west later on. The process starts over again in the afternoon as was displayed in the dual peak diurnal. Once the sun is setting, northern and western paths will decline in activity at a slower rate while southerly and easterly ones may drop off quickly.

“Can one predict when it is the best time to work real DX locations on Es?”
Yes…..
1. If the DX location is primarily east of you… Concentrate your efforts towards the DX station as your Sun has risen and then once again as the Sun’s Grey Line approaches the eastern DX locale.
2. If the DX location is west of you …Concentrate your efforts towards the western DX station as their Sun rises and then once again as your Sun sets.
3. For Northern and Southern DX paths ….Concentrate your efforts along the suns Grey Line as it leaves or approaches both locations.
This approach appears to produce better results.

“Do severe weather systems and the Jet Stream have any affects on Es propagation?”
Predominately it is small to absolutely none.
A weather system may influence Es propagation between two specific points (experienced here a few times), but I found it difficult to correlate its influence over the entire creation of the phenomena. This study covered 560 days of the Spring and Summer season, over a 5-year period. Of the entire seasonal total, I could only determine that an extremely small percentage of PropNET captures had anything to do with weather systems. In these 5 years, 2 of them were drought years with very little jet stream wind flow and little electrically active weather to speak of. If weather was the primary influence, the hourly charts would have represented trends indicative to weather affects. They clearly failed to do so. For three of the four years of the study, the morning daylight period was clearly the best times for Es propagation. Severe weather is a late afternoon, early evening occurrence. Captures in all four years never displayed the highest activity in the afternoon. In addition, Es would have also occurred at high levels in many other times of the season with varying levels. The study does not show that as is shown by its clear absence of captures in early April.

“Are there any other possible external influences that might affect Es?”
Probably meteors increase the probability of Es.
These were the actual daily captures of record for the 5 years of the study.

This is the potential meteor shower rates per hour for each day during the Es season.
Source: DL5BAC’s The Meteor Scatter Predictor Program (TMSP)

It was not perfect for all peaks of meteor activity, but many of the spikes in captures during the 5 years coincide along them. Meteor influence was brought to my attention at the end of the season when there was an increase in Es activity on July 29-30, August 2 and August 13-14 when one would think that activity should have been very limited.

“What might cause the overall lull in activity and probability during the weeks around the Summer Solstice?”
The high angle of the Sun during this period might have an affect on Mid-Latitude Es. The Nighttime probabilities actually peak during the solstice, therefore it points towards the peak during this period. Maybe the heat radiated off the earth, in addition to the high sun angle deters ionization of the Es layer to some extent. The final two years were minimum solar activity years. The lull was much less pronounced during this time.

“Is the term “Sporadic” a proper identification of the Es propagation phenomena?”
Absolutely not.
The Houghton Mifflin Dictionary defines “Sporadic” as:
1. Occurring at irregular intervals; having no pattern or order in time.
2. Appearing singly or at widely scattered localities, as a plant or disease.
3. Isolated; unique: a sporadic example
The 5 years of the study and the resulting charts show that Es display no such conditions of being Sporadic.
Therefore, we should use the opposite term, “Periodic”.
“Periodic” is defined as:
1. Having or marked by repeated cycles.
2. Happening or appearing at regular intervals.
3. Recurring or reappearing from time to time; intermittent.
Periodic appears to be a much better adjective used to describe Spring/Summer Es propagation.

Future Plans:
I encourage that someone in a different location than mine participate in PropNET each Es season. Efforts to improve data collection from the database created by LiveX will make it much easier to produce statistical analysis for more than one PropNET participant and I will look into this investigation in future years as long as there are an adequate number of participants.

I would like to see the research expanded to 6 and 2-Meters. I am sure we would see similar results experienced between 10 and 6-Meters. PropNET 2-Meter activity would produce a much more worthwhile propagation database than what APRS could accomplish. High population of users and the FM mode in APRS mask many of the propagation conditions that occur on VHF. PropNET could be more valuable than CW beacons.

I plan to list on a website a “Daily Probability” of Es conditions. I hope to have someone (or myself) to write a script very soon for general Ham Radio use that displays in date and time, the probability in percentage of experiencing an Es QSO on 10 Meters along with favorable directional data.

Glossary:

Afternoon Active - Most occur in the afternoon daylight hours.

Morning Active – Most occur in the morning daylight hours.

Averaging Data – It was used to smooth out peaks and lulls between actual days and better concentrate data gathered for hourly statistics. Solar Indices are displayed in running averages. It did not change the actual totals if the data displayed was accumulated.

Coefficient of Determination (R squared)- Is a measure used in statistics that indicates how well a calculated regression trend line approximates the actual data points. The scale is measured from 0.0 to 1.00. 1 reflects a perfect correlation.

Diurnal - Webster’s Dictionary defines this term as:
Recurring every day, occurring in the daytime, or opening during the day and closing at night.

Dual Peaked Diurnal – Two peaks of activity occur in the daylight hours.

Es Propagation – The bending of radio waves in the ionosphere at frequencies from approximately 10 – 230 MHz (25-50 MHz most common) by what is known as the E-Layer of the ionosphere (50-80 miles). Due to its lack of its predictability, it is often referred to as “Sporadic Es”. It is also known as “Short-Skip” because it propagates at shorter distances than normal F2 layer propagation at high frequencies.

Median – American Heritage Dictionary defines this term as:
Relating to, located in, or extending towards the middle

Probability Analysis – Based on the premise that one event occurs for a given time period. In the study, a single capture in an hour would have the same value at 100.

Right Skewed – Statistics term used to describe charted data. If most of the data volume is located to the left of center, it is considered right-skewed.

Right Tailed - Statistics term used to describe charted data. If the chartered data declines at a slower rate and time than it first rises, it is considered right tailed.

SE-Prop – DOS and Windows program developed by Jim Roop - K9SE that displays probable E-Cloud location and MUF between two stations.

Summer Solstice – It is the day that the Sun is directly over the Tropic of Cancer (approximately 23.5° North latitude). It is the highest elevation that the Sun will appear in the Northern Hemisphere. It marks the Winter Solstice in the Southern Hemisphere. When the same condition occurs in the Southern Hemisphere over the Tropic of Capricorn (approximately 23.5° South latitude), it is the Summer Solstice for the southern hemisphere and the Winter Solstice for the northern hemisphere.

Solar Noon Hour – The actual time (hour measured) that the Sun is due south. During Central Daylight Time it occurs at 13:18 or 1:18 PM.

Digisonde – A device that measures the values of returned high frequency radio signals transmitted and received in order to determine ionospheric layer altitudes. The University of Massachusetts Lowell Millstone Hill Digisonde is best known.

W6ELProp – Windows computer program developed by Sheldon C. Shallon, W6EL used for predicting ionospheric (sky-wave) propagation between any two locations on the earth on frequencies between 3 and 30 MHz. Earlier DOS versions were known as MINIPROP and MINIPROP Plus.

A Never-Ending Thank You to the PropNET Organization……..

Top 50 PropNET
Rank-Call-Grid Square-Captures
1 WD4RBX EM84NN 8713
2 WB8ILI EN82OQ 5933
3 K4RKM EM85VF 5160
4 W4JKL EM84AK 5026
5 K8VGL EM69UT 4752
6 AD4RX EL88OD 4443
7 KD5LWU DM57RI 2857
8 N7YG DM42NF 2655
9 K4EPS EL86UW 1752
10 NZ9Z EN64BD 1716
11 N4LR EM73QN 1626
12 KC9MEG EN52TI 1358
13 N4PSN EM84KP 1245
14 KI4EIZ EM63KN 1072
15 KI0GU EN35HF 974
16 WN4AMO EL98CW 861
17 KF6XA DM13JO 827
18 N8QLT EN82HL 707
19 KC6QJO DM05KH 701
20 N0OBG EM48RO 659
21 KC0EFC EM28OX 649
22 W3GYK EM85VF 620
23 WN3C FM19QC 539
24 W2EV FN03XD 529
25 AB0TJ DN60CN 514
26 WB8SKP EM56WR 509
27 WB4U EM94QU 493
28 W3NRG DM12JQ 491
29 NI5F EM42UF 459
30 K5BTV EM74WG 376
31 KF9KV EN52ET 374
32 W6CGH DM13BR 347
33 WA0JYF EN42EB 333
34 WB8SKP EN66TD 326
35 WB4JFI EM92XU 314
36 KC0TLN EM28QX 306
37 WV5L DM65PG 275
38 AB9MS EN42XN 268
39 KD5CFB EM40IQ 221
40 AI4NV EL87PX 192
41 K1HOP FN31SS 191
42 W4DDR EM85BW 177
43 NM4V FM06NR 176
44 NH7O BL10WP 162
45 NK8Q FN20GN 153
46 N5XYO DM90QQ 145
47 WD4ELG FM06LA 139
48 N2JR FM18CO 137
49 K3OMG EN82EI 126
50 W7IXZ DN05XJ 122

73s Art Jackson KA5DWI

A 5-Year 10-Meter Es Propagation Study Using PropNet - Part 10

The Final Level of Analysis:
Now that 5 years of data was collected and PropNET participation each year was consistent and the data displayed definitive trends, there still existed a few unexplained holes. Although I averaged combinations of days and hours, most of these charts displayed many peaks and valleys. It stirred up my curiosity and I decided to investigate it on a micro level.

Five years of participation had produced good probability data supported by capture numbers. It was proven that the higher the probability of Es, the number of captures during the occurrence was also higher. With this mind, the volume and incident data was combined to the level of a specific day and specific hour within it. The first attempt using 3-hour averages was not satisfactory. It failed to show extremes. In this analysis extremes need to be tracked in order to show the abnormalities.

In this final analysis, the hourly incidents (probability statistics) from April 25 to August 15 are graded on a 0 to 5 scale. A “0” ranking meant no opening, a ranking of “5” meant an opening all five years. Next, the hourly capture rate for each hour it was open was ranked in a similar manner. The hourly rate was based on the number of annual openings for that hour, not for the 5 year period. For example, if at 15:00 on May 23rd captures were recorded for 3 out of 5 years and a total of 60 captures occurred, a rate of 20 was assigned and applied to a similar scale (0-5).

The final process was to apply a scale based on the overall merit given from both probability and capture rates. The end result identified those events that appear to be special year to year during the Es season.

The Activity Scales:

The first activity scale applied to each hour of each day is one of probability. The low end (violet) will indicate no activity in 5 years. The high end (burnt orange) indicates an opening all five years.

The second activity scale is for capture rate when an opening occurred. It is based on the hourly capture rate as a ratio of the hours open.

The “Overall Rating Scale” is based on the combination of both the probability and capture rate scale. If there was no activity found, the “No Activity” (violet) is assigned. If one opening in five years with 6 or less captures occurred it was assigned “Light” (blue).

When viewing and interpreting these scales whenever it is yellow, orange or burnt orange (good to extreme) are the best times to operate. You will find that this occurs for most of the daytime periods into the median of the Es season.

The “Probable PNP No.” is a representation of the probable number of PropNET participants captured during the event. It may have been less, and possibly more and based on normal PropNET operating procedures.

The Chart:

The first row is the date of the season and the number of days prior to or after the Summer Solstice. The second row is the overall rating for each hour. Each date is displayed from local daylight saving time 12:00AM midnight to 11:00 PM. The third row is the probability rating. The number displayed was the years that an opening occurred. The fourth and final row was the hourly capture rate for those years open.

The results were somewhat startling. There are active days with good to extreme conditions, preceded or followed by poor ones. As this data was compiled, I realized that several of the days that had “Excellent” and “Extreme” conditions were days that I had experienced excellent VHF openings in the past.

By using this method of assessment and additional ranking of the daily results, the best days of each season can be identified. The DX enthusiast can now concentrate on individual days that historically produce excellent results.

60 days (slightly more than half) within the Es season have been identified as to being historically active days. In this review, an attempt to specifically detail traits will be attempted.

Es Activity Calendar:
Now that five years of data was collected, I was able to distinguish those days during the season that displayed excellent conditions. I have identified and ranked the 20 best days of the season for the following criteria:
1. High Rates – When open, a high rate of captures occurred.
2. High Activity – For the 5 years measured, a high number capture rate occurred overall.
3. High Probability – For the 5 years measured, a high number of open hours occurred.
4. Top 20 - Based on the 3 prior measurements, these days were within the top 20 days in the season.
5. Top 60 - Based on the 3 prior measurements, these days were within the top 60 days in the season.

The Best 20 Days of the Season:

The following dates are ranked from the 1st to the 20th.
6/16, 6/30, 7/8, 6/4, 6/3, 7/29, 6/5, 5/22, 6/29, 6/19
6/28, 7/13, 7/7, 6/15, 5/28, 6/13, 7/12, 7/28, 6/12, 6/23

1st Quartile Spring/Summer Es Season (April 25 – May 22):
The scale charting begins at 7:00PM on April 24. It signifies 00:00 UTC April 25. As noted, Es activity is very light and in five years measured, openings occurred for the most part only in one single year. The first evidence of any “good” level of Es activity occurs on the afternoon of May 4. The May 3-5 range shows the elevated levels. The first excellent conditions (orange) occur on May 9 and 10. The openings on this date occurred for only 2 to 3 years but when it was, the capture rates were at extreme levels (burnt-orange).

Activity levels improve and do have some periods less active. With the exception of the May 9-11 spark, the best conditions are during daylight hours.

Es Activity Calendar: April 25 – May 22
May 2: High Rates
May 3: High Rates Top 60
May 5: High Rates
May 7: High Rates
May 8: High Rates
May 9: High Rates High Activity Top 60
May 10: High Rates Top 60
May 11: Top 60
May 15: Top 60
May 20: Top 60
May 22: High Activity Top 20


2nd Quartile Spring/Summer Es Season (May 23- June 21):
The scale charting begins at 00:00 Local Daylight Time (Central) May 23. Es activity during each daytime period is very good (Yellow) in the five years measured. A few excellent hourly openings (Orange) will occur during daylight hours for most days in the quartile. The first evidence of extreme conditions (Burnt-Orange) in Es activity occurs on the morning of June 4-5. Some lulls in activity occur during this period, but are short-lived. 8 of the 20 top activity days occur in this quartile.

The best day of each Spring/Summer Es season is June 16. For 5 five years this date is highly ranked in probability, high hourly capture rates when open, and general high activity overall. The period from June 3 to June 17 are the best times of the season and should be the focus of all DX’ing activities.

Es Activity Calendar: May 23 – June 21
May 24: Top 60
May 26: High Probability Top 60
May 27: Top 60
May 28: High Activity Top 20
May 29: Top 60
May 30: High Probability Top 60
May 31 High Probability Top 60
June 1: Top 60
June 2: High Probability Top 60
June 3: High Activity High Rates Top 20
June 4: High Activity High Rates Top 20
June 5: High Probability High Activity Top 20
June 6: Top 60
June 8: High Probability High Activity
June 9: High Activity High Rates Top 60
June 10: High Rates Top 60
June 12: High Probability Top 20
June 13: High Probability Top 20
June 14: Top 60
June 15: High Probability High Activity Top 20
June 16: High Probability High Activity High Rates Top 20
June 17: High Probability Top 60
June 18: Top 60
June 19: High Activity Top 60
June 21: High Probability Top 60


3rd Quartile Spring/Summer Es Season (June 22 – July 20):
The scale charting begins at 00:00 Local Daylight Time (Central) June 22. Es activity during each daytime period remains very good (Yellow) in the five years measured. Excellent hourly openings (Orange) will occur during daylight hours for about 3/4th of the days in the quartile. A few lulls do occur. Extreme conditions (Burnt-Orange) in Es activity occur midday on June 30. As in the prior quartile, 8 of the 20 top activity days occur also in this one. The second and thirds best activity days of each Spring/Summer Es season are June 30 and July 8.

Es Activity Calendar: June 22 – July 20
June 22: High Probability Top 60
June 23: High Activity Top 20
June 24: High Probability Top 60
June 25: High Probability Top 60
June 26: High Probability Top 60
June 27: Top 60
June 28: High Activity High Rates Top 20
June 29: High Activity High Rates Top 20
June 30: High Activity High Rates Top 20
July 1: High Rates Top 60
July 3: Top 60
July 4: High Probability
July 5: Top 60
July 6: Top 60
July 7: High Probability High Activity Top 20
July 8: High Probability High Activity Top 20
July 9: High Probability Top 60
July 12: High Probability High Rates Top 20
July 13: High Activity High Rates Top 20
July 14: Top 60
July 16: Top 60
July 17: Top 60
July 19: High Activity Top 60


4th Quartile Spring/Summer Es Season (July 21 – August 15):
The scale charting begins at 00:00 Local Daylight Time (Central) July 21. During this period, Es begin a general decline. Still, Es activity during the daytime remain very good (Yellow) well into August. Excellent hourly openings (Orange) occur on July 28 and 29. July 29 has had a history of being one of the top 10 days of the season. Daily lulls become more common place, but no clear end of the season appears until August 15. Extreme conditions (Burnt-Orange) in Es activity do not occur during this period, although excellent conditions will occur as late as August 12. Only 2 of the top 20 and 7 of the top 60 activity days occur in the 4th quartile. The Es season ends quietly within 2 weeks after August 15.

Es Activity Calendar: July 21 – August 15
July 25 Top 60
July 27 Top 60
July 28 High Activity High Rates Top 20
July 29 High Activity High Rates Top 20
August 2 Top 60
August 3 Top 60
August 12 Top 60


Probabilities 8/15 – 8/28:
Beginning 8/15, Es activity begins to decline rapidly. As noted, it is not unusual to experience very good conditions now and then for an hour or two.


Next: The Final Recap, Helpers, Summary, Glossary

A 5-Year 10-Meter Es Propagation Study Using PropNET - Part 9

Hour to Hour Probabilities by Week:
The final analysis performed using probabilities was to compare the hour-to-hour trends of each week in the Spring/Summer Es season. With the volume and sampling, we should be able to identify where changes may occur from week to week of the season. Also, if the data accumulated was reliable, did it provide consistent and reasonable results?

Three Week Periods:
The following chart displays probabilities of working Es in 3-week segments from the beginning to the end of the season. The chart clearly details that the 6 weeks prior to and then after the Summer Solstice (12 weeks total) are the best periods for Es. The one fact that is evident is that during this 12 week period there is not much difference between them.

Weeks 1 – 4:
Week 1 (4/25-5/1) starts the Es season with some limited activity in the daytime hours. In Week 2 the best opportunity is in the late afternoon. Probabilities average less than 9% for Week 1 that on any hour a 10-Meter Es PropNET capture can occur. Probabilities almost double (over 16%) Week 2 and will favors afternoon times.
Probabilities more than double between the 2nd and 3rd weeks. Activity this 3rd week of the season clearly favors morning Es activity and typically forms a dual-diurnal pattern to be seen for other active weeks. Due to increased activity the final year of the study, the 4th week increased due to steady opportunities during the afternoon hours. Most of these weekly periods showed higher probabilities in the latter years of the study.

Weeks 5 – 8:
These are the weeks approaching the Summer Solstice. Probabilities in Week 5 increase over 8% to over 50% overall. Week 6 has the third highest probability of the Es season (near 58%) and had the highest of the season prior to the final year. The local 10 AM through 1 PM hours have probabilities of a 10-Meter PropNET capture at or above 90%.

Despite the high activity of the 6th week of the season, the 7th week (6/06) drops off over 7%. The drop off occurs during the morning hours. Week 8 returns to the level of Week 6 and has a rise in twilight activity that shows that the Summer Solstice is the peak of the season. Once again, this did not show until the latter years of the study.

Weeks 9 – 12:
Week 9 (6/20) is the week than contains the Summer Solstice. It changes little from Week 8 as there is a less than 1% increase, but the week is more morning active. There is a significant (more than 10%) decrease in Week 10, followed by a healthy resurgence of 12.6% in Week 11. This is the week that contains the Independence Day (July 4th) holiday and traditionally is known to be a very active week for Es propagation. Week 12 is unusual in that it declines in afternoon and evening activity. Most week to week declines have occurred during the morning hours.

Weeks 13 – 18:
The usual “morning decline” pattern occurs again in Week 13. Week 14 has a surge in activity is as Week 10. The sudden increase is noticeable from year to year. July 29 is usually active and is one of the more active days each season. The final two weeks, Week 15 and Week 16 also have steady afternoon declines in activity. The declines are slight. Week 16 overall probability is only slightly above 5% lower than Week 13. It was a poor assumption on my part that the Es season ends by August 15. Usually the first activity-free day does occur near or around the date, but Es activity continues until the first of September. By continuing the data collection for two additional weeks, it is noted that activity returns to levels experienced at the beginning of the season and once again becomes truly sporadic in nature.

Conclusions About 10-Meter Es Propagation:

In my 35 years of monitoring and working these phenomena, I have heard many theories as to their generation and occurrence. Some of these theories that have been proclaimed, I personally do not consider them to have any major effect of the trends shown in these charts. I strongly believe that too many have tried to figure out the wonders of Es and ignore the consistencies that it is displaying. Placing its generation of single natural and physical situations and phenomena is difficult to prove. I hoped that this 5-Year Propagation study would dispel many single-cause theories and provide mathematical, scientific, and logical answers based on consistent patterns and trends.

If Es were caused by a specific ionosphere or atmospheric events, consistency and patterns in the charts from the study would not occur. Much is still left to science to find the real cause and a mathematical approach using practical data gathering practices can show the reliability and consistency of the phenomena and dispel these types of theories.

In addition, this study was not compiled in order to predict when your specific 2, 6 or 10 Meter QTH could connect to another specific QTH. It was strictly compiled to identify the best dates, times and possible directions to work them.

Next: The Final Level of Analysis

A 5-Year 10-Meter Es Propagation Study Using PropNET - Part 8

Triple-Hour Probabilities:
To better qualify these observed trends throughout the Spring/Summer Es season, I charted probabilities into three hour increments. I first charted probabilities in 1-hour segments and found the information to be overwhelming. This approach shows the seasonal changes in Es opportunities best.

Arranging the probabilities in this pattern will show that the peak of the season is only clearly evident in late evening, twilight and daybreak hours. It is quite difficult to see a seasonal peak during daylight hours.

A reminder… The 9th Week is the Summer Solstice.

6 AM – 9 AM Local Time:
The sun rises at this QTH during this measured period. Although the right-skewed trend was evident in the earliest hour during this period, overall opportunities consistently rose until the Summer Solstice. During this weekly period one can expect an almost 50% chance of an Es opening. Between the 5th and 14th weeks (5/23-8/01) there is at least a one-in-three chance of an opportunity.

9 AM – 12 Noon Local Time:
This segment is the best time to work Es, and is best to call it “primetime”. By the 3rd Week of the season (5/09) the probabilities are greater than 50% for the entire season. During the 6th Week (5/30-6/05) the probability is almost 90%. During the four years of the study, specifics days and hours within this period had a capture occur each year of the 5 year study. The obvious trend shown is that once the Es season begins in earnest, it will not end until the end of August. The 16th week of the season is just as active as the 5th. Any decline in probability as the season progresses is hardly negligible until Week 17.

12 Noon – 3PM Local Time:
The probabilities during this segment clearly indicate and confirm that Es propagation is a daytime (diurnal) phenomenon. The probability of working 10-Meter Es is only slightly lower than the previous 3-hour period. The pattern continues until the Sun approaches due south, the Solar Noon (1:15PM). The 6th Week again is clearly the best and we also begin to notice a slight mid-season lull. The probabilities of a 10-Meter capture are at their best at the noon hour. During this time segment a slow a steady decline appears after the 11th week of the season.

3 – 6 PM Local Time:
The sun is now located further west during this period. The right-skewed and right-tailed progression of the season shows up in this segment. The 6th week of the season was the best until 2009 and had me believing that Es activity was peaking at a period other than the summer solstice. The 11th week displays a very strong rebound in opportunities. The 11th week of the season (Independence Day 7/4) it is well known by many Es enthusiasts as an extremely active week. Much of the rise could be due to an increase in the population of participants during the holiday, although many PropNET participants vacationed.

6 – 9 PM Local Time:
During the latter time in this segment the Sun sets. The right skewed and right tailed probability trend is quite evident in this chart. Seasonal trends are clearer with only the 11th Week showing a sudden surge in probability. This time period best displays the rise and fall of the Es season. By the 3rd week, probability of an Es QSO is above 50% during the time segment and remains at least that high until the 16th week of the season.

9 PM - Midnight Local Time:
For each hour after sunset, overall probabilities continue to decline. Other than the 11th week surge, the decline is quite pronounced beginning the 8th week. The best weeks again are the 6th, through the 8th. As in the daytime segments, by the 5th week probabilities are greater than 50% and remain so until the 12th. A slight increase the 14th week becomes apparent and prevalent into the next 3-hour segment.

Midnight – 6:00AM Local Time:
Probabilities of an Es QSO become much less into the twilight hours. The trends displayed are consistent; probability peaks near the Summer Solstice. Generally when opportunities occur at these hours, Es have been very intense. Some of the best daily openings with numerous high MUF QSOs have occurred when good conditions exist at these hours.

Also, notice that the 14th week peak in probability has now shifted to the 15th week. It brings up some interesting questions to why weekly peaks occur at these early morning hours.



Next: Hour to Hour Probabilities by Week

A 5-Year 10-Meter Es Propagation Study Using PropNET - Part 7

Probability Analysis – A Better Method to Predict “Es” Activity:

Due to the fact that the United States’ distribution of population and Ham activity was not equal, a better measurement practice is to apply an equal value to one single reception (PropNET capture) within a one hour period. In other words, a single occurrence in a measured period equals the occurrence of many. The probability of an occurrence is now measured, not the actual number of captures in the period.

Therefore, every hour documented and measured in the 5 years of data was re-applied. If a capture occurred during the hour it was given a value of one (1). If no capture occurred, it was given a value of zero (0). The result is that statistical probabilities can be applied to any set of days and hourly times in which an opening occurred. The quality and quantity of the hourly opening had no bearing. Opportunity is what is being measured, not how much was being worked.

The key factor is that opportunity will always produce results. The more opportunity existed, the better the results.

The following charts data are based on these factors:
1. The days prior to and after the Summer Solstice (June 21)
2. All 24 hours are used in the day.
3. The probability measured (percent) is that on any hour of that day, we will have at least one occurrence of a 10-Meter PropNET Es capture during any hour.

The results show a very clear trend on how Es begin, increase and then decline during the season. Daily total probability is based on that on the day measured, that on any measured hour, the occurrence of a 10-Meter Es PropNET capture occurred. It was amazing to see the daily differences with 5 years of cumulative volume data. Once difference shown between capture and probability data was that the “median” date for captures was on 6/22 and for probability it was 6/25 a 3 day swing. In other words captures are spread evenly throughout the season, but opportunities slightly favor the second half of the season.

Some probabilities can increase or decrease 30% in one day. As in the total captures chart, the Probability Chart represented the dramatic increase in opportunities in early May. The best day for Es opportunities was after the summer solstice (June 25 and July 4), with 65% of the total hours on these dates having a capture. By May 21, the occurrence of an Es capture for any hour of the day increases to near 50%, and remains fairly consistent for most days until July 29. One factor that draws your attention is why there are certain days less productive than others. The right skewed and tailed appearance in probability is somewhat clearer than the capture volume statistics as the season takes about 2 more weeks after the solstice to finally end.

The regression analysis performed on probability is much better than the one performed on capture statistics. The coefficient of determination is at the upper end of measurement. The trend line indicates that the season begins on April 26 and ends on August 30. The peak for probability occurs on June 27. This trend clearly indicates that Es probability actually favor the second-half of the season.

As in the capture charts, I averaged 3 continuous days of data around the day measured. As in the daily charts, it was surprising how much probabilities will decline or increase in a matter of a couple of days. Still the early seasonal increase, followed by the slow decrease the second half of the season was quite evident.

This trend becomes much clearer when 6 consecutive days of probabilities are averaged for each measured day. Note that both the beginning and end of the Es season are clearly defined.

After measuring hourly probabilities on a daily basis, I decided to measure cumulative weekly periods to further confirm trends that I had seen in the prior charts. Also, I wished to see how probabilities of a capture changed for the actual hours within a day. I again divided the Spring/Summer Es season into 16 weeks. I compiled 7 day segments of data for the 5 years and calculated the probability that at least one capture occurred at any given hour in this weekly period. In 2009, I extended the measurement period by 2 weeks.

Probability Statistics by Hour:
I was also curious to find out if the probability factors would also correlate to a higher number of captures. Probability is based on a single incident during a measured hour, not on total captures. I was very pleased to find out that the two factors did relate closely. Only during the late afternoon were there minor shifts. This might be due to the shifts of average distances (higher) experienced during this period. The shift is negligible. Therefore, quality relates to quantity.

The regression analysis performed for the hourly probability closely represents a typical day on Es that begins at the 6:00AM hour. The peak in terms of probability occurs at 1:00PM local daylight time. The trend then shows a general decline till 5:00AM.

Probability by Weekly Periods:
The following charts are represented and discussed in terms of the week of the Spring/Summer Es season. When it is referenced, each week number corresponds to the following days:

WEEK BEGINS - ENDS
Week 1: 25-Apr - 1-May
Week 2: 2-May - 8-May
Week 3: 9-May - 15-May
Week 4: 16-May - 22-May
Week 5: 23-May - 29-May
Week 6: 30-May - 5-Jun
Week 7: 6-Jun - 12-Jun
Week 8: 13-Jun - 19-Jun
Week 9: 20-Jun - 26-Jun
Week 10: 27-Jun - 3-Jul
Week 11: 4-Jul - 10-Jul
Week 12: 11-Jul - 17-Jul
Week 13: 18-Jul - 24-Jul
Week 14: 25-Jul - 31-Jul
Week 15: 1-Aug - 7-Aug
Week 16: 8-Aug - 14-Aug
Week 17: 15-Aug - 21-Aug
Week 18: 22-Aug - 28-Aug

As shown in the Daily Probability figures, similar trends with the weekly capture computations did occur. Before 2008, the peak of the Es season was the weeks beginning May 23 and May 30 (5th and 6th week). The final 2 years of the study strongly showed the peak after the Summer Solstice (early in the 9th Week). On average, a slow decline begins after the 9th week. The small peak during the week of 7/25 (14th week) also draws your attention and will be addressed later.

By the 5th week of the season, daylight period probabilities become consistent week to week and maintain the high probability levels. The evening and twilight periods (8 PM-6AM) will show rates of change before and after the solstice. The daytime period weekly probabilities changed little once the season was in full swing.

When the study was started, my opinion was that Es activity should form a perfectly shaped bell curve peaking at the Summer Solstice. Throughout the 5 years of this study, it was quite evident that capture totals and probability calculations once charted were showing that Es activity was somewhat right-skewed and right tailed. In other words, Es activity once the season begins rises quickly then peaks before the Summer solstice. Activity then slowing declines for the remainder of the Es season. The end of the Es season will occur further after the Summer Solstice than when it begins before.

Next: Triple Hour Probabilities

A 5-Year 10-Meter Es Propagation Study Using PropNET - Part 6

Es Directional Characteristics:
One of the characteristics of Es to observe was to compare PropNET captures between different directional groups. Due to the varying volumes from each directional group, the following capture data is displayed as an “hourly percentage of the total day” for each group, and not the actual volumes. This allows us to compare groups to each other on an equal scale. Each hour charted was also based on a 3-Hour average method. For the most part, each directional group displayed similar trends. Peaks and valleys were usually no more than two hours off between directional groups. Only the Southern/Southwestern group was different and peaked during the other group’s lulls.

Specific Directional Groups:
After five years of this study, there existed sufficient information to display the specific peaks of activity towards 45-degree directional segments. Although it made statistical sense, it tended to cloud up the trends it was indicating.
The actual number of captures by 45-degree segments was as follows:
Direction Captures
North-2167
Northeast-18806
East-32258
Southeast-2090
South & S. West-151
West-5631
Northwest-3660
As indicated, the numbers strongly point to an Easterly influence due to the number of participants over the years. To best display similarities and contrasts, comparing directional groupings seemed to be a better approach to show trends.
New Methods to Compare Directional Data:
After reviewing each directional group, distinctive patterns were apparent between them. Each group is separated into the following halves:
1. North and South
2. East and West
3. Northwest and Southeast
4. Northeast and Southwest.

Comparing North to South:
The following charts shows that as the sun rises, the opportunity to work stations towards the North (270° - 89°) is greater than Southerly (90° - 269°) ones. Both directional groups show the steadily improvement after sunrise. Both groups peak the hour prior to noon. Northerly opportunities decline after noon at a pace much greater than Southerly ones during this time.

A second peak of activity begins for both groups during the local 5 PM (17:00-17:59) hour. This helps confirms a dual-peaked diurnal pattern for both opposite directional groups. Once the sun sets, opportunities decline more rapidly for the Southerly group. The sun is located north of west at and after sunset from my QTH.

Therefore, Northern paths are best as the sun rises and as it sets. Southerly propagation is strongest during the afternoon hours when the sun is at a high elevation. The sun’s influence is quite notable.

Comparing East to West:
Separating the total data into these directional groups (East and West) show one obvious trend, follow the sun. Eastern capture opportunities are better than the Western ones after sunrise and peak during the local 10 AM hour. Activity declines steadily and peaks again during the 5 PM hour (the dual-peaked diurnal). Western capture opportunities improve at a slower rate after sunrise and peaked at the 1 PM hour (3 hours later). The Western activity decline after sunset is less than the Eastern counterpart, but opportunities after midnight become best to the east.

Comparing Northwest to Southeast:
Separating activity into Northwest and Southeast halves show that the sun’s location determines the best paths by time of day somewhat equally. Both show the dual peak diurnal. Of all the directional half groups, these two directions tend to stay closer in the hourly trends. The hours from sunrise to mid-afternoon show the only differences.

Comparing Northeast to Southwest:
Finally, the “follow the sun” scenario is more apparent for Northeast and Southwest divisions. Peaks in activity are clearly two hours different. Northeast occurs at 10 AM and Southwest at the Noon hour. For both directions, the late afternoon peaks are almost equal with a slight favoring towards the Southwest.

Performing a regression analysis on the data shows that during the course of the day the only differences seem to be from North to South. Southerly tracks seem to peak early in the daytime and decline quicker. These trends are minor for the most part. As shown the Es day begins when the sun comes up and ends during twilight hours.


Next: Probability Analysis

A 5-Year 10-Meter Es Propagation Study Using PropNET - Part 5

Distance Analysis:
One of the characteristics of Es that might be unknown is how propagation of the E layer changes during the course of a day. I noticed into the second year of the study that many of the longer distance captures were occurring late into the afternoon. Using the distance calculation and data provided from the PropNetPSK software for each station captured, I was able to determine the average distance of the captures (in kilometers) for each hour of the day.

As I suspected, the longest distant PropNET captures do occur late in the afternoon during the 5 and 6 PM (17-18 on chart) local hours. Throughout the 5 years that data was collected, most of the longer distant captures would occur during this period and raise the average capture distance. This was contrary to the higher number of captures that occur in the morning. The long distance captures to Hawaii, Puerto Rico, and the northeast and northwest corners of the United States would occur late in the afternoon. In the morning daytime hours as 10-Meters becomes active, average distance declines as activity increases followed by a steady increase throughout the afternoon. As sunset is approached, distance declines steadily until 10 PM. The late evening and early morning peaks were influenced by the appearance of NH7O in Hawaii.

Using the 3-hour averaging method produces very similar results as well. The longest distances for 10-Meter captures peak at 7 AM, 5 & 6 PM, 11PM and 2 AM local time (Central Daylight).

There is not much difference in the MUF of E clouds at the charted distances (SE Prop). At 1330 kilometers, the MUF of the Es cloud is 32.1 MHz. At 1390 kilometers, the MUF is 31.5 MHz. At 1430 kilometers, the MUF is 31.1 MHz. The questions that are raised:
1. Is a lowering or rising E-Cloud MUF resulting in longer distance captures, or are there more aligned Es clouds with adequate MUF’s that are creating multi-hop opportunities?
2. Are the reflective characteristics of Es in the morning hours different from those experienced in the afternoon?

Es Distance Statistics:
To make better judgments on how Es occur by distance, all 5 years of captures were separated into 500 kilometer segments beginning at the 750 kilometer mark. Clearly, the vast majority of Es captures at this location occurred from stations within in “1250-1750” kilometer range (775-1090 miles). The next largest segment was “750-1250” kilometers (470-775 miles), which totaled less than half of the largest group.

Including the closest range (0-750 kilometers), a morning active dual-peaked diurnal is quite clear for distances to 1750 kilometers. As the distance extends beyond 1750 kilometers the dual-peaked diurnal exists, but becomes afternoon active.

1250 – 1750 Kilometers (775 – 1090 miles):
The vast majority of Es propagation occurs at the 1250-1750 kilometer level. Whenever Es first develop on 10-Meters, signals generally appeared within these distances first. Again, the best time for propagation is clearly during the morning hours after sunrise occurs. At the normal height for an E cloud (105 km) and at this range midpoint, the MUF for the cloud is approximately 30.4 MHz (SE-Prop). The range closely resembles the overall captured trend experienced.

750 – 1250 Kilometers (465 - 775 miles):
The next most active distance is was at the “750-1250” kilometer range. These distances tend to occur as overall Es intensity increases. It also is a way to determine that MUF has increased and help forewarn of further opportunities on 6 and 2 Meters. Similar to the previous distance segment, it favors the morning hours after sunrise. This range clearly displays the dual-diurnal pattern. At the midpoint of this range, the MUF is approximately 38 MHz (SE-Prop).

1750 - 2250 Kilometers (1090 – 1400 miles):
Within the “1750-2250” kilometer range (1090-1400 mile), the majority of these captures are more than likely double reflections (hops) of signals at the Es layer. At 2000 kilometers, the MUF of a normal Es cloud is at 28.3 MHz (SE-Prop) and minimal for Es propagation. The first indication of an afternoon active diurnal occurs at these distances and influences the average distance increase.

0 – 750 Kilometers (0 - 465 miles):
For this segment (0-750 kilometers), Es are extremely intense. Reflections of 10-Meter signals are probably at lower levels in the E-layer. At 750 km, the MUF of a normal Es cloud is approximately 46 MHz. Some of these paths experienced equated to a MUF greater than 90 MHz (SE-Prop). I have witnessed the beginning of several 2-Meter Es openings when these 10-Meter paths were extremely short. Also worth noting, although these short paths favor morning hours, the “absolute” shortest paths in this study generally occurred in the late afternoon hours. Past experiences working VHF Es indicated that these captures (< 300 km) were actually Es backscatter. It was not uncommon to see this phenomenon on 6 Meters as well.

2250+ Kilometers (1400+ miles):
These final distance segments noted (greater than 2250 kilometers or 1400+ miles), represent multi-reflections of 10-Meter signals within the E-layer. Approximately 2300 kilometers is the farthest distance for single Es on 10-Meters (SE-Prop). Two aligned clouds that have an MUF of 33-34 MHz would support it. It does not represent F2 propagation because during the 5-year study, solar flux was not a high enough to create the required F2 MUF (near 18 MHz from Digisonde readings and propagation prediction programs such as, W6ELProp). 10-Meter Es propagation at these distances clearly does occur in the late afternoon hours and were fairly rare in occurrence until 2009. For the first 4 years, the furthest distances experienced in the study and charted below were between my QTH and Puerto Rico. In the final year were more numerous captures from Hawaii.


Next: Directional Analysis

A 5-Year 10-Meter Es Propagation Study Using PropNET - Part 4

The Time of the Day That Es Occur:
My belief from practical experience and with other researchers was that Es seemed to be best in the late afternoon/early evening hours. I have discovered in this analysis that it was the morning hours towards midday that are the best time for Es. More operating activity from Hams generally occurs during the later hours of day, and that was the probable cause for the assumption. The afternoon hours are still very active, but not to level experienced in the morning hours. The afternoon hours still have unique characteristics.

In addition, all time charts are displayed in Daybreak (Sunrise) to Daybreak (Sunrise) order. At this location, the sun rose in the 6 AM (6) CDT hour and sets during the 8 PM (22) CDT hour. 10-Meter Es were decisively diurnal (daytime-patterned). Therefore, it was best to display all results in daytime hours first, followed by evening and twilight hours.

The following chart is the number of Spring/Summer Es captures by hour for each year of the study. After seeing different Diurnal patterns between 2005 and 2006, this encouraged me to do a third year of participation to determine a true pattern. The 2006, 2007, and 2008 data would look similar in many regards. The final year (2009) would display an equal “dual-diurnal” pattern. What I got out of these charts was that each year does have similar trends, but each has its own distinctive personality.


Once again to better display hourly trends, the next chart is displayed as a 3-hour average. For example, the plot for 6 AM is the average of 5, 6 and 7 AM. Averaging does not change the overall totals. This method works best in demonstrating what Es actually do for hour to hour.


After accumulating the 5 years together, it was very clear to see that Spring/Summer Es are diurnal and are generally better during in the late morning hours. Once the sun rises, Es rapidly increase. Once the sun sets, Es decline sharply. Most dominant in 2007, 2008 and 2009, the overall chart shows a “dual-peak” diurnal pattern.


A regression analysis on the actual data clearly indicates that Es begin at 6 AM local daylight time. During the solar noon hour (13:00) Es peak and then begin a slow decline throughout the remainder of the day, evening and twilight hours.


Hourly Activity Week to Week:
The following chart displays 3-hour average captures for the 16 week Spring/Summer Es season (8 weeks each side of the Summer Solstice). The 6th week of the season is the most active and clearly appears similar in trends to the overall seasonal data chart. The 8th week grew rapidly the last 2 years and had a distinctive dual diurnal peak. The 1st, 2nd, and 13th weeks are least active, but clearly show a diurnal pattern as well. Only the early and latter weeks of the season fail to show a dual-peaked diurnal pattern.


Next: Distance Analysis