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Help interpreting tuner specs

These are the readings from my old tuner after testing: Distortion @ 1 kHz - 100% modulation

Left Wide IF mode 0.053% Narrow Mode 0.18%
Right Wide IF mode 0.054% Narrow Mode 0.18%

Stereo Separation @ 1 kHz - 100% modulation

Left into Right Wide IF mode 64 dB Narrow 57 dB
Right into Left Wide IF mode 63 dB Narrow 56 dB

65 dBf RF input quieting - unweighted (Signal to Noise Ratio)

Mono -72 dB
Stereo -75 dB

50 dB quieting points - unweighted (Sensitivity)

Mono 0.5 uV
Stereo 22 uV

Do these readings represent good tuner specs?
byegolly

Showing 2 responses by almarg

almarg's avatar
almarg
9,670 posts
 
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
almarg's avatar
almarg
9,670 posts
 
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
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