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<p>Hi Scott,</p>
<p>You are correct that I usually think in terms of "voltage" as
that's the way the code has to be written. However, the -6dB
level of each tone relative to peak, as displayed on the
panadapter, is correct no matter whether you think of "voltage" or
"power". Note that the panadapter display is labelled in dBm
(Power) however, it is actually generated by taking the envelope
[sqrt(x^2+y^2)] of the FFT output of the complex I-Q receive
"voltage".</p>
<p>Say we start with a voltage at a level of 1.0. If we reduce it
by a factor of two, we have 0.5. The corresponding dB reduction
is 20*log10(0.5/1.0) ~= -6dB. Now consider that P=V^2/R. So, the
power was reduced by a factor of 0.5^2=0.25. The corresponding dB
reduction is 10*log10(0.25) ~= -6dB.</p>
<p>The key point in my previous message was that the DAC and
amplifier are being driven to the same peak envelope level no
matter whether you have a TUN signal, an SSB signal, or a two-tone
with the generator level set at 0.0dB.</p>
<p>73,</p>
<p>Warren NR0V<br>
</p>
<br>
<div dir="ltr">On 11/24/2016 6:44 AM, Scott Traurig wrote:<br>
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<div class="gmail_extra">I am not surprised that you think more
naturally in terms of voltage, Warren, as one of your primary
goals is to obtain a particular set of voltage conditions on a
DAC.</div>
<div class="gmail_extra"><br>
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