Hi Stuart,
Not to argue the toss, but...
In all my 35 years in the international telecom industry, I never ran across
dBmw. All our voice-frequency (VF) level meters were calibrated in dBm.
0 dBm = -30 dBW = 1 mW, independent of impedance. We had 75-ohm selective
level meters (for multiplex alignment) and 50-ohm RF power meters which were
also calibrated in dBm.
Cheers for now, 73,
Adam VA7OJ/AB4OJ
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]On Behalf Of Stuart Rohre
Sent: Monday, July 28, 2003 12:02
To: tentec@contesting.com
Subject: Re: [TenTec] dbm and VU units of audio measurement
Ken,
You are thinking of dbmw dB re one milliwatt; and the VU "Volume Unit" both
of which are usually spec'd across 600 ohm impedance. VU was used in radio
Broadcast consoles while the dBmw was in the phone company audio trade. The
VU was damped in a meter having a certain ballistic characteristic, to more
easily judge speech and music levels.
73,
Stuart
K5KVH
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