HVDN Notebook: Blips that Bleep: CAGR & ARRL Field Day Analysis

Lets talk about compound annual growth rates (CAGR) which is used to figure out the growth of something over a certain period of time. The equation for that calculation is:

The benefit of using CAGR is that it smooths out anomalies to not be distracted by the so called "blips" in data.

Using CAGR is not the best way to determine trends nor is it the best methodology for different forms of forecasting.

However, showing how to use CAGR for data that an amateur radio person may understand is the goal here through the ARRL Field Day analysis lens.

Yes, I just did use the word "blip" in a somewhat scientific way. Here is what I mean in real life context.

Blip: Using data we understand?

The ARRL Field Day event is an annual exercise where groups or individuals who have amateur radio licenses see who can make the most radio contacts in a 24 hour period in the last weekend of June.

For over 80 years, this event sponsored by the ARRL has been taking place and as its name implies, has a strong focus on field operation compared to just sitting at home.

This event gamifies a level of preparedness in a very social way which also teaches different readiness skills. Overall, it is a lot of fun.

Until COVID, it was always encouraged to get outside or use emergency power or temporary antenna to help see how effective everyone could be in less than optimal conditions for ARRL Field Day.

But, because social gathering during a pandemic and involving higher "health/age risk" populations is not a good idea, some temporary rule changes for how field day operates have been made in 2021 and 2022.

There are different classifications of participants. The "D" class stands for a home participant doing nothing different than normal. The "A" classification is for fully off grid powered and temporary antenna based club stations.

There are other classifications such as B, C, E and F as well with specific definitions which covers everything from single portable operators to those involved in a county emergency command center locations.

Different classes for the masses?

The number of transmitters capable of being on the air at the same time is appended to the station class. For example, a 1D is a single operator at home using one transmitter at a time.

Another example would be the 4A which would be a club operating totally temporary from some location other than home and using four transmitters at any time. The 1B1B class is a pair of operators each using a different radio and/or antenna.

Rule adjustments due to COVID basically permit at home stations (Class D) to aggregate scores up to Class A clubs if they would like in order to show support.

But, this is not reflected in the total stations participating which is why looking at station classes is a good way to look at this event.

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A copy of the ARRL Field Day 2021 rules can be found here: https://contests.arrl.org/ContestRules/Field-Day-Rules.pdf

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We need charts: Lets look at some interesting data now thanks to the HVDN ARRL Field Day Tracker tool.

The above table shows the top 20 station classifications in ARRL Field Day in 2019, 2020 and 2021. Each column shows the total number of stations categorized in each of those classifications. This does not show participants, but the actual station classifications.

Blip Blip: 3 Year Data Analysis

Looking at only 3 years of data covering 2019, 2020 and 2021 we see some interesting data, but it is not really possible to call these a trend. Why? It is because of the BLIP in 2020.

Do you see the huge BLIP in the table above? If you missed it, have a look at the Class D data in 2020 and 2021.

Before COVID, it was really rare to make contact with a 1D and 1E station during the event, if we look just at 2019 pre-COVID results. Using CAGR in this small data set does not tell the whole truth, especially when factoring in the 2020 "blip" year.

With about 2,926 stations, which is different than total participants, taking part of the event in 2019, it almost appears that the COVID years show huge growth in total stations.

However, looking at the data, its clear that those who stayed home as 1D stations did nothing different than turn on the radio and do anything differently than normal operation.

The "E" class trend which is home based, but emergency power based stations is surprising how much it grew in 2020 but shrank in 2021. However, this is still well above average normalcy based on a 12 year long data set available.

Overall, it is really hard to analyze these 3 years against each other to discover the true health of amateur radio via the lens of ARRL Field Day.

More Data: Lets look at the 10+ year CAGR trends instead

To really understand these trends about who is operating during field day or how, we really need a wider data set, so lets looks at 2010 to 2019 separately for now.

In the above chart, its pretty clear to see that Class A stations have been declining before COVID was even known about.

The Class D stations have been slowly rising. The Class B family of operators has also been increasing. What does this tell us from 2010 to 2019 data?

Amateur radio clubs (Class A) are starting to decline in how they approach Field Day.

At home stations (Class D) grow with many reasons such as health, safety and age contributing .

The B class 1-2 person portable running battery increases.

The emergency power at home Class E stations are increasing.

The 12 year bigger picture about ARRL Field Day

Data tends to scare people, especially if it provides fact versus opinion.

Looking at just the numbers for 12 years of total ARRL Field Day Data, it is hard to find trends unless you analyze data as your profession.

Getting back to using Compound Annual Growth Rates, we can show trends either over a span of 3 years (2019 to 2021), 6 years (2016 to 2021) or the full 12 years (2010 to 2021). We can also look just at 2010 to 2019.

If we color code the CAGR values to show red as below zero percent, yellow as between zero to ten percent and green as greater than ten percent, here is what that looks like.

The below charts are for all field day data and not just for specific regions. It is a complete view of the overall event.

Reading the below charts

Red = Less than 0%
Yellow = 0.001% to 9.999%
Green = More than 10.000%

The below three charts (C1, C2, C3) isolate by color this table to allow for more focused analysis.

Lets talk about the "Red" Cells

Values that you see as -100.00% are no cause for concern. In some years, there were no stations that operated as those classifications in the growth period, so that data needs to get tossed out. Same with the one cell that lists 0.00% under the Class BC. Same goes with the EB Class.

This leaves us with something important to talk about relative mostly to Class A operation.

No matter how we look at the data and model for growth, it is clear that larger club operations are starting to slowly decline.

It is not high single or double digit declines yet, but it is worth thinking about as we enter what is hopefully a growth cycle thanks to increasing sun spots in Cycle 25 which we are only just starting to benefit from for HF communications.

The ARRL is already marking Cycle 25 as being important to amateur radio which I agree with completely, so lets hope this is true and we see larger Class A operations increase again.

Chart C1

Lets talk about the "Yellow" Cells

A great point to highlight is that no matter what time period calculated in the data above, overall we see some type of growth.

The Class B family of stations really need to be focused on as a positive as well along with continued growth within the Class E stations participating in ARRL Field Day.

Chart C2

Lets talk about the "Green" Cells

While few and far between, since these only include growth over 10%, given that the event is called "Field Day", it seems slightly wrong to look at this growth as a positive when talking about Class D stations here.

However, if more Class D can convert to off grid powered Class E stations, that is a move in the right direction.

If the ARRL can find ways to encourage the use of battery power via large power banks, that could maybe start moving home stations back out into the field.

Bulky and dangerous gas powered generators might be worth considering being taken out of service to encourage more green technology to be used in the future. This can prove a very large benefit thanks to the ARRL perhaps leading this green energy change.

Chart C3

Regional Analysis of ARRL Field Day

The HVDN ARRL Field Day Tracker tool was built upon publicly available data available from the ARRL. Some of the data analysis additions added include an FCC Region and aggregate class tracker.

These additions help illustrate regional differences easily in additional to divisional and sectional differences in data. Without pointing fingers, here is what would be interesting to readers in the Hudson Valley.

The goal is to interpret this data and see what trends can be determined or any improvements or adjustments be made for how almost everyone may approach field day in the future.

FCC Call Region Two ARRL Field Day - By Class with CAGR