Radio Propagation 101

With NOAA declaring the end of solar cycle 23 and the beginning of cycle 24,

This would be a good time for a mini review of radio/solar propagation, and

The terminology that we use in the Ham Radio community. Solar conditions

Directly effect HF conditions and our ability to receive and transmit, and to

A greater degree than we might think for VHF and UHF transmissions.

The easiest way to get a quick overall view of conditions is to check the

Current Solar Flux report, which is easily obtainable on QRZ.com (main menu-

Solar report) or my favorite, www.wm7d.net. A quick glance at the SFI number

And A & K indexes will give a good indication of what bands are open and

What condition they are in. The Solar Flux index, the higher number the better,

Is an indicator of how much ultraviolet radiation from the sun is ionizing our

Upper atmosphere, and supporting refraction of our radio signals. The A & K

Indexes represent the effect that the solar radiation has on the earths magnetic

Fields, the A index a 24 hr average worldwide, and the K index an on the spot

View of worldwide readings. We want the A & K numbers to be low, higher

Numbers mean plenty of noise and interference, possibly resulting in radio

Blackouts, power grid disruptions, and a fringe benefit, beautiful auroras.

Of course, sunspots are the main generator of cosmic radiation, being magnetic

Regions on the sun, that due to temperature differences, appear as dark spots

On the face of the sun.

The average sunspot is easily the size of the entire earth. And presently being

Exactly between solar cycles, there are days with few or no sunspots. During the

Peak in the last 11 year cycle in July of 2000 we had 401 sunspots, which meant

To ham operators on HF you work Japan on 10 meters with 10 watts! The

Highest solar flux number was 298 in October of 2003, which means talking to the

Entire world on low power on a simple modest antenna.

I have the WM7D website in my computer in the favorites, and each morning I

Take a look at conditions and put them on a post-it in the ham shack. Its always

Your guide to conditions and a great topic of conversation among hams. Cycle 24

Is expected to be good and will create some great operating conditions over the next

Few years, again each cycle lasting 11 years. Volumes have been written about every

Aspect of this subject, especially for those of us who love chasing DX contacts in the

Far corners of the planet. This information is our guide to current conditions and how,

they they are going to be. Much more information can be found in researching the

Computer, ARRL publications, or the magazines (QST/Popular Communications etc)

For wealth of information. For even more join ARCARS and attend the meetings,

And socialize with your fellow hams, and get involved in emergency communications

In our community. We look forward to meeting anyone who wants to share in the

Common goal of serving the community and enjoying ham radio.

73’s and great DX!

Tom/W8TRC

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