[sdiy] Equation for converting V PP to dBm?

[Justin Owen]

Hello,

I've been researching how to convert a Peak to Peak Voltage into dB and I've come up with 4 slightly different equations which all give different answers. I've also had a few different people tell me that different ones were the 'right' one - so I thought I'd ask here.

1) dB = 20*log_10(Vpp/0.707)
2) dB = 20*LOG10(Volts_peak_to_peak/SQRT(0.008*Z))
3) db = (20log10) (RMS ) & RMS= 0.707*P-P
4) dB = 20 log10 (Vout / Vin)

Recognise any of them?

What I'm trying to do is plot the response curve of the 2164 based on the data sheet spec of -33mV/dB. I figure if I can convert V PP to dB I'll also have mV to V PP.

Takers? Thanks.

Justin