Do you really know when the best time is to go on air?

Foundations of Amateur Radio

Getting on air and making noise is a phrase that you've likely heard me repeat often, actually, this will be the 24th time or so. It's an attempt at encouraging you to actually transmit and use the radio spectrum that is available to you. It's a nicer way of saying: Use it or lose it!

One of the more frustrating aspects of our hobby is finding other people to interact with. At the beginning of your hobby you have access to all these magic radio frequencies with no idea on how to use them. Often a new amateur will turn on their radio, call CQ a couple of times to see if there's anyone out there, hear nothing and give up.

As you get more experience you'll discover that radio frequencies change over time and that some work better at certain times of the day. This is reinforced by others who will talk to you about propagation, the solar cycle and how the ionosphere and its various so-called layers will change and what you can achieve throughout the day, the year and the long term cycle.

Armed with all this knowledge you are likely to get to a point where you make noise on a certain band depending on the time of day.

For example, experienced amateurs will avoid the 10m band at night because it's a so-called day-time band, in other words, their perception is that you cannot make contact on the 10m band after sunset and for the same reason, it's not suitable for early morning contacts.

What if we could test that perception and see if it's true or not?

Turns out that we have a perfect dataset to discover what actually happens. If I look at the 10m band WSPR or Weak Signal Propagation Reporter data for the past year, a year that had me using a beacon pretty much 24 hours a day, you'd expect that you could see just which times worked and which ones didn't. Turns out that regardless of time of day, my beacon was heard across every hour of the day. Of course the numbers aren't uniform across the day. The peak is at noon local time, the trough is at 5 am local time, 10% of reports are at noon, about 1.5% at 5 am. In other words, the worst time of day for my beacon to be reported is 5 am in the morning and it's not zero.

Interestingly the same isn't true for the signal to noise ratio, a measure of just how weak or strong a signal is in comparison to the local noise at the receiver. If you account for differences in transmitter power, meaning that a stronger transmitter is measured in the same way as a weaker one, the 10m band has the best signal to noise ratio at my location at 9 pm local time and the worst at 4 pm local time.

Given that I'm only using the 10m band with my beacon I also looked at the local OF78 grid square across all bands. It shows that reports are not directly related to when the average signal to noise is best. It seems to me that people are transmitting when they think it works best, not when it actually works best and I'll mention that the definition of "best" depends on each user.

Note that I haven't yet sat down to discover if there are automatic transmitter and receiver pairs that have been reporting 24/7 across a year on the same band to determine if there is more to learn about the relationship between how often something is reported and what the signal report was at the time. I can say that it's likely that your favourite band is more popular when others think it's popular, not when the conditions are better.

Consider for example that there are no local reports on the 12m band at 10am, but there are at 9am and 11am, so, was the band magically unusable the whole year at that time, or did people just not use it? The same is true for 160m. No reports at all before 5pm or after 3am, despite the bands around it having contacts throughout the day.

I will point out some things I've ignored. For example, what is a useful contact? Is it measured by distance, by quantity, by uniqueness? Is this choice the same for each band? Is it reasonable to compare a whole year, or should it be by some other time period, like month, season or lunar month? What is the signal to noise ratio for a band that's considered closed?

I'm mentioning this because each of those will directly affect what it looks like when you create a chart and it's likely to change what works best for you.

So, next time you get on air, try a band that shouldn't work according to your knowledge and see what happens. Perhaps you'll get lucky, make a contact and discover something unexpected.

I'm Onno VK6FLAB