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dB is the most common measurement parameter used for RF amplitude

Notice that dB is a ratio not a specific quantity but let's see how it is used

dB=10 Log((Vout2)/Rout)/((Vin2)/Rin)

Many times we shorten these formulae by using a fixed reference.

dBm, which means dB relative to 1milliwatt = 10 Log Pout/1*10-3

dBuv, which means dB relative to 1 microvolt = 20 Log Vout/1*10-6

If you change the signal voltage by:

Frequency is 1/time that it takes for an oscillating signal through a particular

Wavelength is the distance a wave travels from a particular state or voltage until

it reaches the same state or voltage. Wavelength is important for calculating

possible sources of emission problems.

In air, the relationship between wavelength and frequency is:

(Speed of light)/F = (3*108)/F

1MHz has a wavelength of 3*108/1*106 = 300 meters

10 MHz has a wavelength 3*108/10*106 = 30 meters

30MHz has a wavelength of 3*108/30*106 = 10 meters

This last wavelength is an important one. The emissions test for commercial

and industrial products starts at 30MHz and the

most common measurement range is 10 meters.

The FCC and European emissions test is to be a far field test.

If you recall from any school training about antennae, we would like an antenna to be 1/4 or

1/2 wavelength long. I would like for you to have a feel for antenna effectiveness.

One of the most powerful stations in my area is KNX-1070. Calculating

the wavelength of 1070KHz we find.

Frequency = 1070KHz Wavelength = 280.4 meters

Frequency = 100MHz Wavelength = 3 meters

Frequency = 1GHz Wavelength = .3 meters = 11.7 inches

SIN(wt) + 1/3 SIN(3wt) + 1/5 SIN(5wt) + 1/7 SIN(7wt) + …

where "w" is the radian frequency or 2*PI*F

= 1/2VDD + SIN(wt) + 1/2SIN(2wt) + 1/3 SIN(3wt) + 1/4 SIN(4wt) + 1/5 SIN(5wt) + …

**There are other sites of interest:**

DNB Engineering: www.dnbenginc.com

Garwood Labs: www.garwoodtestlabs.com