[R-390] Line Level meter

[ka9egw at britewerkz.com]

Having solved the mystery of the 3rd wire...one of my sub-projects is
figuring out the dropping resistor to use with a physically-correct 1mA
meter movement [matches the 390 meters but it's just a 1mA DC meter, no
internal rectifier/cap like a true VU meter] and a bridge rectifier to make
a Line Level VU meter .

0dBm is 1.228Vrms, so for 0dBm to be half-scale...lessee...check my math
here...1.228vrms=1.754v peak, or 3.508v pk-pk.  That makes 0dBm is 3.5V
[assuming a capacitor-input filter so output approximates Vpk-pk w/a bridge
rectifier].

However, the meter face .pdf I can print repro meter faces from looks to
have 0dBm at about 2/3 scale, which means 3.5V at 0.67mA equals 5.22K ohms.
5.1K ought to be close enough, whaddya think?  Or ~2.4K with a single diode?
No need to worry about what to do with the cold end of the bridge that
way...

Thanks,
Brian KA9EGW