Maybe dBv stands for dB "variable," not dB with respect to a volt.
Once you get used to it, the relative reference can be of some benefit.
For example, set dBV to 0.0 at the bandwith peak and then the dBV
reading gives you a direct reference to how many dB down from the filter
peak you are when doing a filter bandwidth scan.
Jack K8ZOA
Jim Brown wrote:
On Tue, 16 Sep 2008 17:29:46 -0400, Joe Subich, W4TV wrote:
As Stef says, you must first set a reference (AFV) before the
dBV (relative change) value has any meaning.
That MAY be how it's programmed, but that would not be right. 0 dBV
is quite well defined by international standard as 1 volt RMS. 0 dBu
is defined as 0.78 volts. Both of these are purely voltage
measurements, independent of impedance. 0 dBm is 1 mw -- to measure
it, one must also know the impedance. 0 dBu is the voltage that
would be present with 0 dBm in 600 ohms.
73,
Jim K9YC
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