[sdiy] Equation for converting V PP to dBm?

Tom Wiltshire tom at electricdruid.net
Sat Dec 31 14:33:47 CET 2011


On 31 Dec 2011, at 13:04, Justin Owen wrote:

> ...and this: http://www.sdiy.org/juz/2164_comp_CV_DB_01.jpg - which shows CV against DB.
> 
> Interestingly, as Andre mentioned - my measurements start to fall off below approx. -40dB / 0.05 V PP - but I'm pretty sure I can work on that.

I had a discussion with George Hearn about this at SDIY UK 2010. He'd been studying the SSM2164, and noted that the VCA drops off sharply to zero at the far end. He didn't consider it a problem since it closes the VCA completely, which is probably what you want. Although I don't remember him saying that he'd see the effect from -40dB onwards, more like -80dB.

But he had spotted the same pattern, so you're seeing a chip characteristic, not a measurement effect, I reckon.

T.





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