Help interpreting tuner specs
Those all look like fine numbers, except that I'm a little uncertain about the 50db quieting points. The 0.5uv mono sensitivity seems too good to be true for 50db quieting. And while I believe 22uv is a fine number for stereo, I'm a little uncertain because most tuner specs these days use dbf units rather than uv. Hopefully someone else will comment further on those two numbers. Regards, -- Al |
I did some calculations on the 50db quieting numbers, to convert them to dbf (decibels above a femtowatt, which is a quadrillionth of a watt). If the tuner's antenna input is 75 ohms (i.e., a coaxial connector), 50 db quieting occurs at: Mono: 5dbf Stereo: 38dbf If the tuner's antenna input is 300 ohms (i.e., screw terminals that accept 300 ohm twinlead), 50 db quieting occurs at: Mono: -1dbf Stereo: 32dbf The stereo numbers appear reasonably decent but not exceptional. The mono numbers, as I indicated above, appear to be too good to be true, and I suspect represent a mistake. You can find the numbers for a great many tuners here: http://www.fmtunerinfo.com/specs.html Regards, -- Al |
I agree with Al, these look like extremely good numbers. I find measured sensitivity numbers a bit difficult to correlate on my own test bench, and there are a few sources of possible error. First, many FM generators (like my old Sound Technology 1000A) have a 50-ohm output, so you need to use a matching network for proper calibration of the output into either a 75-ohm or a 300-ohm antenna input, and add the attenuation of this network to the signal-level dial calibration. Second, I find that there are a handful of RF-noisy devices around my bench, and sometimes don't feel like turning them all off to get a super-precise measurement. And there's the matter of the disparity of your mono vs. stereo readings - if the composite or pilot modulation level on the signal generator is off a bit, then it will show up here. But if your tuner is indeed acheiving the performance you describe . . . it's working just fine. |
