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Badly Labelled Gubbins

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burakkucat:
Earlier today I was looking at the label on the back of some gubbins. It read --

Frequency: 1600 Hz
Level:      -10 dB
Impeadance: 600 Ohms

My initial thought was "O.k. Perfectly normal" but then my eye returned to the second line. Minus ten decibels . . . relative to what?  ???  High tide level at Newlyn? One volt? One milliwatt? One watt?

An experiment was duly performed. The gubbins was connected to a Rheostat No. 1A, set to 600 Ohms. The gubbins was turned on and the AC voltage across the load was measured with a Fluke 8022B DMM. A value of 0.242 V was observed.

The power = (0.242)2 x 103 / 600 mW
          = 0.0976 mW

That power is equivalent to 10 x log10 0.0976 dBm
          = -10.1 dBm

Finally, to convince myself that the arithmetic is correct, the gubbins was connected to a Level Measuring Set No. 35A configured to terminate the circuit with a load of 600 Ohms. A value of -9.9 dBm was observed.

I suspect that seeing "Level:      -10 dB" and automatically knowing that dBm is the relevant unit would be second nature to those of our members who are escapees from the Newgate Street empire.  :D

[Edited to insert the correct values.  :-[  ]

licquorice:

--- Quote from: burakkucat on July 06, 2018, 09:43:36 PM ---I suspect that seeing "Level:      -10 dB" and automatically knowing that dBm is the relevant unit would be second nature to those of our members who are escapees from the Newgate Street empire.  :D

--- End quote ---

Indeed so!

4candles:

--- Quote from: burakkucat on July 06, 2018, 09:43:36 PM ---I suspect that seeing "Level:      -10 dB" and automatically knowing that dBm is the relevant unit would be second nature to those of our members who are escapees from the Newgate Street empire.  :D

--- End quote ---
You took the words out of my intended reply.   ;D

burakkucat:
When I typed the word "escapees" I had two particular members in mind. Two members who, over the past years, have helped me understand the finer points of various topics . . .

b*cat makes one of his Japanese-style bows.  :)

4candles:
Reciprocated <in ungainly British way>   :)

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