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"Jay Heyl" wrote http://www.wunclub.com/sounds/index.html That's an interesting site. Does anyone know of a site that has examples of signals at various SIO/SINPO ratings? I usually put down some kind of rating in my logs, but I'm never sure if my idea of "barely audible" is the same as anyone else's. It would be nice to have some kind of example of various ratings from more experienced folks. ================================================ Here is some help from a perhaps dated guidebook issued by NASWA Understanding Your S-Meter DXing According to NASWA - 4th Ed. 1979 by Edward Shaw Without a doubt the S-meter is perhaps one of the most misunderstood pieces of equipment associated with our hobby. The S-meter may be used by the hobbyist to aid him/her in evaluating an incoming signal. To begin with, it may be best to explain briefly that the S-meter is a simple voltage meter which measures the output strength of the first IF transformer in a receiver. The stronger the signal, the higher the IF output voltage, resulting in greater needle deflection on the S-meter. The measurement shows strength in decibels above a given standard. The word decibel derives from Alexander Graham Bell, thus a 'Bel' was a single measure, and deci-bel meant 10 Bels. Each S-unit is nominally double the value of the preceding unit. That is to say, an S-6 reading is twice as much signal as S-5, etc. The typical S-meter is marked off in units from S-1 to S-9 with graduations after that for 10, 20, 30 or more decibels above S-9. An S-meter gives only relative strength of stations heard. A reading of S-9 on one receiver may not be S-9 on another receiver, even using the same antenna in the same location. However, this is only because manufacturers cannot or do not adhere to one standard. One prevalent standard among many professional manufacturers of communications equipment (and the U.S. military complex)is to adjust S-9 on the meter for a 60 microvolt laboratory signal. This would mean that an S-meter reading of S-8 would be 30 microvolts; S-7 would be 15 microvolts, and so on down to S-1 which would indicate something less than 1/4 microvolt. Depending on the sophistication of the receiver at hand, and its ability to give an appreciable signal-to-noise ratio, the S-meter needle actually may never register below S-3 or so due to the noise level itself keeping the needle deflected up that far. Only under the most controlled laboratory conditions can a manufacturer's claims of .... i.e. "1/4-microvolt" sensitivity be realized. In reality a 1/4 microvolt signal amplified sufficiently enough to be audible probably would be so lost amid the amplified noise level as well, that it would be undetectable. In practical use of your S-meter to aid in adjudging a fairly reasonble SINP evaluation, the following guidelines are offered. They may or may not be accepted by radio station engineers or other DXers. Only the S factor is SINPO is considered here, and one should not confuse it with evaluations for QRM or QRN (respectively I and N of the SINPO code). Graduations between S-1 and S-9 may vary in accuracy from meter to meter, and from receiver to receiver. S5 - The best possible local quality strength. The carrier wave alone of such a signal will do much to suppress QRM or QRN. The S-meter reading is in excess of 20dB over S-9. S4 - Strong signals between S6 and +20dB. Voice and music are comfortably readable. Slight QRM and/or QRN may be present. No trouble following complete program with full understanding. S3 - S-meter is S-4 to S-6 and music is readlily identifiable. Voices are clear enough to follow the gist of what is being said (or would be if you understood the language). S2 - S-meter registers between S-2 and S-4. Familiar tunes are still recognized, but with difficulty after some moments. Can still differentiate between male or female announcers. Can possibly still ID the language by tone, inflection, gleaned words, etc. S1 - S-meter is less than S-2. Cannot determine whether male or female. Cannot recognize tunes or language. Noise level is likely to be much louder than the signal itself. In the last case, an ethical listener cannot claim certainty of identification, and the only guide to suspects will be reports of others who have heard a better signal from such a station. |
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