Confused about AIM manual statement

[denniskb7st]

Hi Bob,

July 23, 2010 of AIM4170 manual. Is there are typo in the equation? It looks like we are given the loss at 10 mHz as 1.5 dB. Then the number 10 is used in the formula, which results in a much lower loss.

Page 35
For example, if the loss at 10MHz is 1.5dB/100feet, enter 1.5/SquareRoot(10) = 0.47 dB/100 feet for the loss. This attenuation value is close to the value at 1MHz. You can enter loss as either a positive or a negative number, it doesn’t matter

In the TLW program, I chose Belden 8263 and it reports .322 db/100 feet. At 10 mHz, it reports loss as 1.032 db/100 feet.

Dennis

[Bob]

Hi Dennis,

The number in the SquareRoot function is not the frequency itself but the ratio of two frequencies, which in this example happen to be in the ratio of 10 to 1.

The loss goes up as the square root of the frequency. For example, the loss at 50 MHz would be 2.236 (=Sqrt(5)) times the loss at 10 MHz. Alternatively, it's approximately the loss at 100MHz divided by the sqrt(2).

--73/Bob