Our local ARES group recently got an NVIS (Near Vertical Incident Skywave) antenna for tactical HF communication within the County. During a couple of test drives of the antenna with the group we tested from 6 meters to 80 meters just to see where we could poke holes. As with all things HF, and perhaps especially with NVIS, solar conditions and time of day played a large role in what we could accomplish.

For Reference

Since we have been doing testing more often it seemed it would be nice to have a quick reference for the club. So we created a page for the club to use as a quick reference on local solar conditions: https://www.ab0pc.org/index.php/examslicensing/solar-weather/

The Antenna

The antenna we are using the the Radio Oasis EZ NVIS antenna. It is a 4 wire antenna with it’s matching unit 12-15′ off the ground in the center of the 4 wires. Here’s a link to the antenna: https://www.cheapham.com/ez-nvis/
Below are a few pics of it setup.

The antenna worked great and was quick and easy to deploy with a tripod. We found having the matching unit lower to the ground seemed to clean up the sound.

From KI0PF

During an NVIS exercise with the club in which KI0PF was participating, mark an I (KE0LTD) had established a very solid NVIS connection between North and South Park. I asked him in a follow-up email if he would provide any resources on solar weather that he liked.

We have a really cool resource directly available to us – the Boulder Ionosonde, which gives near-real-time ionograms.  Here’s the real-time link: https://www.ngdc.noaa.gov/stp/IONO/rt-iono/latest/BC840.png

Here’s a backup link: https://lgdc.uml./common/ShowRandomIonogram?ursiCode=BC840

Clicking on either should give you the latest ionogram, which plots frequency on the X axis and height in km on the Y-axis.  I’m still learning the interpretation of the graph, but the immediately useful data to us are the two lines at lower left “D” (distance in km) and “MUF” (maximum usable freek).  The one to look at is the first one at 100km, which will give a pretty good idea what will be most likely to work at the 0 – 60mi ranges we’ll have inside the county or to Denver, etc.

Just as cool, you can see the historical Boulder MUF data for every hour of every day in 2019 here:


That’s how I got the data for the hours of the SET on the 26th.

Reading Ionograms

At first glance the charts may not make a lot of sense. Below is a great video that explains how to interpret the charts.

Additional Resources

This is a great resource for lots of other graphs from Boulder and other stations: https://region6armymars.org/resources/solarweather.php

You can view all of the available stations in the participating network here: https://www.digisonde.com/stationlist.php

And if you really want to go nuts on the details you can start with this presentation: http://indico.ictp.it/event/a11159/session/87/contribution/57/material/0/0.pdf

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For quick reference, there is also a solar weather widget in the footer of our site

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One Responses

  • Mike Carrington

    It was a pretty slick QSO because I, in Littleton, got to contact someone in South Park. I like the antenna, too.

    But I’d really like to know the relationship between solar storms, solar wind, solar flux, geomagnetic activity, all the other sun related information AND HF Conditions. I do not know what these things mean. How do they relate or affect distant communications?



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