[IRCA] Defining S#'s without an S-meter?

[Stephen Airy <pianoplayer88key@xxxxxxxxx>]

Hi all.  I was wondering how you would define/interpret S# signal strengths if you didn't have an S-meter, or the radio you were using didn't have one?  Would you base it in part on the quality of the received signal, for example?

I don't have that type of S-meter (the PL-380 and PL-606 use different scales).  I usually base my interpretations on the "S" definitions of the RST scales, like follows...

S0 "no reception" (not on scale) - self-explanatory, not even a carrier trace

S1 "faint signal, barely perceptible" - anything from a carrier trace to copyable audio with extreme difficulty, requiring a quiet area, good quality headphones, and a channel free of QRM from other stations

S2 "very weak signal" - readable with some possible difficulty, but still very noisy & weak.  Desensed PL-606 signals reading 50/00 would be rated here at best, even if they might otherwise be S6 or S7 without the desense.

S3 "weak signal" - easily readable, but still at a reduced volume with some noise.  Also signals that would be stronger on the PL-606 but are desensed (for example 50/15) would be rated here or below.

S4 "fair signal" - about the weakest a scan will stop or a tuning indicator will be lit.  Also this is approximately where the perceived volume of the signal audio is near its maximum.  Weaker signals often sound "quieter", with the noise level staying the same, or below S2 or so the noise AND signal both get quieter.  Stronger signals sound just as loud with a reduction in background noise.

S5 "fairly good signal" - some noticeable noise with the signal, but quieter than with S4.  My reception of 640 KFI, 740 KBRT daytime and 1070 KNX is about here on some radios.  On my PL-606 they indicate around mid to upper 40s dBu or so.

S6 "good signal" - there may be a little background noise noticeable between talk beds in a quiet environment with good headphones.  Music or road noise in a car would mask that noise however.  Typical PL-606 readings are approx. 52-58 dBu or so.

S7 "moderately strong signal" - with very few exceptions, there is virtually no background noise audible with the signal.  (My PL-606 is one exception, as it seems to have some noise even with S9 signals.)   On a radio with poor selectivity like the SRF-M37W, the first-adjacent splash will sound just as loud as if not louder than the main channel.  PL-606 readings are typically in the 60s dBu range.

S8 "strong signal" - Loud splash on poorly-selective radios extends to ±2 or 3 channels.  PL-606 on-channel readings typically range from about 70-82 dBu or so, with 2nd-adjacent desense typically 39/00 or 41/00 up to 47/00.

S9 "extremely strong signal" - if a station has audible intermods at other spots on the dial, chances are it's an S9.  Loud splash on poorly-selective radios extends ±4 or more channels, with the weaker splash in extreme cases audible over much of the band.  On some radios the first-adjacent splash sounds different with a reduced volume - for example the Sangean DT-400W within 1/2 mile of a 50kW transmitter.  PL-606 signals are typically 83-93 dBu with 2nd-adjacent desense approximately 49/00 or 50/00 (in extreme cases spreading as wide as or wider than FM stations for the 50/00 and across much of the band for 49/00).  I currently have no stations rated this high, but when the KCBQ site was in Santee (50kW @ 6 mi daytime) I rated them here.

S10 "overload" (not on scale) - signal is overloading the audio stage and sounds distorted on-channel.  On the PL-606 this starts around 95 dBu and is well underway by max scale at 98 dBu.  Usually I have to be within 80 to several hundred feet of the tower depending on power.  In somewhat severe cases occasional blips of unintelligible modulation is heard, then stronger ones sound like an open carrier.  This happened within 10 feet of one of 2.5 kW 590 KTIE's tower, for example, where I'd guess the field was a few hundred or so volts/meter.  In extreme cases distorted audio is heard all the time, even when the radio would be otherwise muted like when switching bands or first powering it on.  (This probably would happen less than a few inches from a 50kW tower.)

As you can see my scale doesn't have S9+xx dB readings - the next is S10.  So how do you interpret the numbers and definitions?

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