Hello Gary,

You've posted some interesting information.

I wondered about the inherent non-linearities and, of course, the
deviation at which the SINADs were measured is not known, either. So the
question boils down to whether modern VHF receivers for marine use are
likely to have noticeably different sensitivity performance.

As you know, SINAD is a measure of "useful sensitivity" and the noise
plus distortion part of SINAD (rather than the signal part) is what is
probably affecting the differences in VHF receiver SINAD measurement.

Taking the issue into the realm of the real world, Icom quotes the
following for their IC-F4GT/GS radios:

0.3 microvolts for 12 dB SINAD
0.79 microvolts for 20 dB SINAD

The TK3160E UHF Transceiver reports similar results:

0.25 microvolts for 12 dB SINAD
0.63 microvolts for 20 dB SINAD

These both work out to Meindert's results very closely. So we know that
by assuming linearity, we are not necessarily wildly out of the ballpark.

I'm not sure how you derived the distortion percentages you mentioned,
but normally a receiver's distortion figure would be measured with an
input signal on the order of 0.5 to 1.0 volt to ensure that noise
doesn't affect the measurement. Under these conditions, a SINAD reading
of 12 dB corresponds to 25% distortion, while a reading of 20 dB
corresponds to 10% distortion.

73,

Chuck