[ARC5] Audio power output - 10 meter BC-454

[Brian Clarke]

Sorry Ken,

You have slightly misread Neil's info.

The correct formula for power is (Erms)^2 / R.
For a sine wave, Epeak = 1.414 Erms.
So, (Erms)^2 = (Epeak)^2 / 2, and therefore, P = (Epeak)^2 / 2R.

73 de Brian, VK2GCE.

On Sunday, February 17, 2013 11:23 AM, you said:


> On 17 Feb 2013 at 13:07, Neil wrote:
>
>> I make it a shade over 300 mW RMS.
>>
>> 17.5 V peak x 0.707 to get the RMS voltage (12.37).
>>
>> E^2is 12.37 x 12.37= 153.02
>>
>> E^2/R = 153.02 / 500 = 306 mW
>>
>> 73 de Neil ZL1ANM
>
> Oh. So I am still wrong: P-P = RMS * sqrt2, whereas PEAK is 1/2 P-P.
>
> OK. Your result actually makes more sense, since the original power output 
> rating for the BC-
> 454 was supposed to be 300 mW.
>
> So the correct formula is E(peak)^2/R=P, and not E(p-p)^2/R
>
> Even so, it is still plenty loud enough for speaker output. I am using a 
> Radio Shack 8 ohm CB
> speaker with a 500:8 ohm transformer in it, so the impedance of the result 
> is 500 ohms
> average...,at least at some frequency in the range...
>
> Ken W7EKB