RSN instead of RST?

Here’s a guest post from Lou, VK5EEE…..Dan

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Radio experimenters, as we once were, have an important duty to give reliable signal reports so that we can gauge propagation, the efficiency and radiation patters of our antenna systems, etc. However, the RST system was devised long ago when we did not suffer from “local noise” from all types of electronic junk. Instead, in those days, others suffered from our interference.

Our most pressing problem that is threatening amateur radio is probably the rising noise levels that make our communication on any mode more and more difficult. Yet, we have no way to inform the other station of the real signal strength of their signal, if their signal is below our local noise level. Nor do we have a way to express the current local noise level which would be of interest to the other station, and also for the general collection of data about rising noise levels, and noise in city locations, and some countries where it is worse e.g. China and Korea.

Those active on short waves will notice that it is not possible to have QSO with stations in BY and HL unless you have a very strong signal, they just will not hear you with a local noise level often above S9. The same is the case for some hams in western cities too, and many YB hams and other countries where there are, as in Australia, no enforcement of manufactured or imported gear EMC specifications.

The T in the RST system is now perhaps superfluous, since 99.9% of CW signals now have a T9. Also one may argue that the S meter system is ambiguous since different radio gear give different S meter readings for the same signal strength, and, almost always HF amateur radio signals have QSB that makes the S meter signal strength vary by at least one, and often two or three S points or more. Does one give the “average” S value? Or the one at the start of the QSO? Or the maximum value? Some will even give the range e.g. RST 55/79 meaning from S5 to S7. I wrote about a simpler 5 point signal strength the same as the QSA code where it is easy by ear to judge the signal strength 1 being barely audible, 2 is weak, 3 average, 4 strong, and 5 exceptionally strong.

However, after talking with my friend Tim VK3IM this evening, we arrived at the conclusion that we really need a new “N” value to determine the (S meter) level of noise. Thus, in an SSB signal a report of RSN 498 would indicate readable without difficulty, signal strength S9, and a local noise level of S8. Or in CW, RSTN 4998. Or, RSN 498 as the T value is always 9 in any case.

Take as example, a local noise level of S5. How far below the noise will you be able to hear? Perhaps S3, but not less. I conducted tests with a sound engineer ham in PA-land and discovered that myself and other very experienced and skilled telegraphists could copy signals up to 13dB below noise level provided they were not too fast, and with some repetitions, and 10dB below noise without too much difficulty. Given that an S meter unit is supposed to be 6dB (but could be 4dB on some radios designed to trick buyers into thinking they are more sensitive), this means around 2 S points. So with a noise level of S5 one would be unable to copy a signal less than S3 (in CW) and SSB is worse, one cannot copy SSB below noise level.

Therefore a signal report of RSN 357 would make a lot of sense: you are having difficulty to read the signal (R=3), the signal is estimated to be S 5 as you can barely copy it, with the local noise level at S7. This is far more meaningful than RST 359 — why is your signal R=3? Because of other stations QRM? If yes, they can add QRM. If due to atmospherics they can add “QRN”. But if it is local noise, there is no real code for it (and there should be) but also, how much local noise? Knowing the other station has a local noise level of S7 is interesting and puts it all into perspective.

Likewise, if you are on an amateur band with the current local noise level on an empty frequency at S3, then you will give a report for that same S5 signal as RSN 553 or RSTN 55N3 (5593).

What do you think? Is it not time that we start measuring and sharing (optionally, should we wish) our local noise levels? Would that not be interesting? The RSN (RSTN) system would be, we think, the easiest way to do this without re-inventing the RST system. CW stations may optionally leave out the T and send an RSN report, just as those on phone, since T is always 9 anyway.

I’d be interested in your replies, and some of us may like to start giving RSN reports — I am sure hams would be very interested to receive an RSN report of say 586 and would quickly work it out what it means. It may be quite fun to start using it and see if others also adopt it, or comment on it. In any case, it will not be difficult to publish and popularize this method of RS(T)N signal reporting via such means as Wikipedia and other reference points.

I look forward to hearing your views.

All best wishes (73), long live CW and wishing you many happy CW QSO (77) de Lou, VK5EEE

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