Playing Radios at Night: Twenties and the Petroglyph National Monument POTA

I made one QSO, was heard in Costa Rica, and maybe found a wavelength tall natural antenna tower in Albuquerque. Here's a view from below of the mesa the POTA station was situated on.

Park:

Petroglyph National Monument POTA K-0955.

Radio Details:

Radio: RockMite 20

Antenna: Halfwave dipole

Happenings of Interest

Shyoooo, I was tired. I spent a few minutes debugging the lack of audio when I turned on the radio. In the end, the answer was...... I hadn't plugged in the headphones. I was so tired. It's been a week.

Here's the thing though: the antenna was 5.5 ft off the ground during most of the POTA. And, as you might expect from reading any number of ham radio books that exhort the amateur radio neophyte to build a tower as soon as possible, I only made one QSO, to a station a few blocks away. (Actually, I thought that was pretty cool! That might have been the shortest QSO the RockMite ever made.) As you might not have expected—I certainly didn't—the radio was heard in Costa Rica... Repeatedly.... on the RBN. And that's the only station that spotted the RockMite, the one in Costa Rica.

See that last spot of the evening? The antenna feed point was eight inches off the ground at that point. Yes, the final transistor of the RockMite is very forgiving.

So... how? I've got a theory. I don't have the experience to know if there's anything to this at all, but I have a theory. Referencing my favorite page on antenna height vs. elevation angle, I found the following diagram and table relating dipole height to elevation angle.

In the following, pay particular attention to the antenna results when the dipole is a whole wavelength above ground.

Armed with my antenna data, I started making observations. I was on top of a mesa. Here's a nice picture of the site from Google Earth:

The white path leads off to KG5WPZ who boomed in from a few blocks away. The yellow line runs roughly perpendicular to the dipole, and extends out to Cost Rica ala

Notice that the two lines intersect at the cedar that was one of the dipole supports, about twenty meters back from the edge of the mesa. Turns out, the mesa was also very close to exactly twenty meters above the surrounding neighborhood. Did the dipole—even virtually sitting on the ground—think it was on a wavelength tall tower? Maybe. Let's do some math.

The distance to Costa Rica from the mesa is 3,450 kilometers. Half of this distance is 1,725 km. The ionosphere as measured by hmF2 at three different—kinda nearby—ionosonde's was in the neighborhood of 435 km up. In Boulder, the ionosonde mostly due north of here, the height for hmF2 was 423.9 km. Taking the arctan of the height hmF2 divided by the distance to the midpoint—so assuming a single skip in other words—gives an elevation angle of 13.8 degrees, not so far off of 13.7! There's a snag though. All three ionosonde's note that their MUF is below 14.0584 MHz, the frequency the RockMite was working on most of the evening. I mean the ionosphere clearly was working from New Mexico, because I don't think the RockMite can ground wave all the way to Costa Rica.

If you're interested in the math, I'd love a check on this.

QSO Log

Callsign	rx RST	tx RST	Time (GMT)	Frequency
KG5WPZ	599	599	02:37	14058.3 kHz

POTA tx QSL:

QSL rx album:

References

POTA (Parks on the Air)

Austin Ionogram:

https://lgdc.uml.edu/common/ShowIonogramPage?mid=51670281&ursiCode=AU930&time=2023.04.24%20(114)%2002:45:05.000

The Valentine's Day Magnetic Monopole

There's an assymetry to the form of the two Maxwell's equations shown in picture 1. While the divergence of the electric field is proportional to the electric charge density at a given point, the divergence of the magnetic field is equal to zero. This is typically explained in the following way. While we know that electrons, the fundamental electric charge carriers exist, evidence seems to indicate that magnetic monopoles, the particles that would carry magnetic 'charge', either don't exist, or, the energies required to create them are so high that they are exceedingly rare. That doesn't stop us from looking for them though! Keeping with the theme of Fairbank[1] and his academic progeny over the semester break, today's post is about the discovery of a magnetic monopole candidate event by one of the Fairbank's graduate students, Blas Cabrera[2]. Cabrera was utilizing a loop type of magnetic monopole detector. Its operation is in concept very sim

Cool Math Tricks: Deriving the Divergence, (Del or Nabla) into New (Cylindrical) Coordinate Systems

Now available as a Kindle ebook for 99 cents ! Get a spiffy ebook, and fund more physics The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems , there seem to be fewer explanations of the procedure for deriving the conversion, so here goes! What do we actually want? To convert the Cartesian nabla to the nabla for another coordinate system, say… cylindrical coordinates. What we’ll need: 1. The Cartesian Nabla: 2. A set of equations relating the Cartesian coordinates to cylindrical coordinates: 3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system: How to do it: Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables. The chain

More Cowbell! Record Production using Google Forms and Charts

First, the what : This article shows how to embed a new Google Form into any web page. To demonstrate ths, a chart and form that allow blog readers to control the recording levels of each instrument in Blue Oyster Cult's "(Don't Fear) The Reaper" is used. HTML code from the Google version of the form included on this page is shown and the parts that need to be modified are highlighted. Next, the why : Google recently released an e-mail form feature that allows users of Google Documents to create an e-mail a form that automatically places each user's input into an associated spreadsheet. As it turns out, with a little bit of work, the forms that are created by Google Docs can be embedded into any web page. Now, The Goods: Click on the instrument you want turned up, click the submit button and then refresh the page. Through the magic of Google Forms as soon as you click on submit and refresh this web page, the data chart will update immediately. Turn up the:

Copasetic Flow

Search This Blog