Sunspots Poor Predictors of Propagation

By David, on June 26th, 2009%

I just read this in the “ARLP026 Propagation de K7RA” from the ARRL and I found it quite interesting and thought it was quite worthy of sharing with you.

It was written by Red Haines, WO0W of La Crescent, Minnesota, USA.

“Though we use the sunspot number and the solar flux index to assess propagation expectations, there is only an indirect connection between these indices and propagation.  Neither sunspots nor the radiation measured by the solar flux index directly increase or decrease the levels of ionization in the ionosphere.  All three are determined, somewhat independently, by physical processes on or in the Sun.

“Sunspots and the solar flux are . . .

To read the rest of this article, please click here: → Sunspots Poor Predictors of Propagation

Leave a comment   Reference, Solar

Decibels in Amateur Radio

By David, on June 18th, 2009%

The decibel was originally used by the telephone companies to quantify audio signal gains and losses in telephone circuits. The original unit was named the “bel” after Alexander Graham Bell, who was the inventor of the telephone.

In most electronics work, however, the bel is too large a unit, so we use the decibel, which is one-tenth of a bel.   It’s referred to as “dB.”

In radio, the decibel is the expression of the ratio between two signals. The signals might be voltages, currents or power levels.

The formula to compute the decibel using the ratio of 2 power levels is:

dB = 10 LOG (P1/P2)

Where . . .

To read the rest of this article, please click here: → Decibels in Amateur Radio

Leave a comment   Antennas, Around The Shack, Reference