Propagation Experiments: Signal Strength vs. Tide Levels

Sometimes you get an idea about two variables that might depend on each other, so you look to see if there's a correlation. That's science. What happens not as much is that if the variables don't correlate, or at least they don't seem to, you should publish anyway. The lack of a relationship can in fact be new information. So, along those lines, here goes.

We activated US-0757 twice last week. In both cases, we deployed the TouCans vertical antenna on a pier with the ground wire submersed in the Bay waters below. In both cases, one of the Utah RBN stations that spotted us suddenly had very high signal levels with respect to our station on 20 meters. On the second day's activation I happened to notice that the water seemed closer to the pier when the signal dBs went up than it had been at the start of the activation. As it turned out, I was correct about the water level so I graphed tide levels vs. TouCan's signal into Utah.

It turned out there wasn't an obvious correlation. It makes sense to me that there would be as, essentially, our ground was coming closer to the feed point of the antenna. No dice though. Here's a graph of the data:

Both days saw an out of kilter peaking of the signal. It was near the maximum tide both days, but the signal strentth data, to my eye does not correlate with the tide heights.

Grabbing Tide Data

If you too would like to chart your favorite (possibly) dependent variable against tide heights in the San Francisco Bay, you can get data on a web page freom

https://tidesandcurrents.noaa.gov/waterlevels.html?id=9414290

or in a programatic JSON format at

https://api.tidesandcurrents.noaa.gov/api/prod/datagetter?

product=water_level&application=NOS.COOPS.TAC.WL&begin_date=20241030&end_date=20241031&datum=MLLW&station=9414290&time_zone=GMT&units=english&format=json

The measurements are taken out at Crissy Field.

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