Still learning here so hopefully the conversation went ok
No man, it was a great contact. Clear, to the point, etc.
BTW, since you asked about RST and I'm not sure I gave you a clear definition, I will expand on it a little. RST means 'R'eadability, 'S'trength, 'T'one.
So when people say 'You're 5 over 9', 'Got you 59' or something similar, what they are giving you are two things.
The first number is a subjective readability and the second signal strength. The third is tone, which is not used with phone modes (i.e. voice).
So the first is 1 to 5, 5 being clear as sitting next to you and 1 being barely able to understand (obviously anything under 1 would be unintelligible). So I had Marco at R 3 to 4 most of the time, which means I didn't have trouble making out anything you said but there was noise, interference, etc. This could indicate you need more power, different antenna, a better mic, to roll up the windows, etc. In our case it was mostly just interference over the RF link, so power increase, higher gain antenna, etc.
Since most of us are using 2m mobile and handies, the strength is easy to estimate from the meter on the radio. Most of them have 9 bars, dots, numbers or something. You simply use that as a guide to determine received signal strength. Our contact was bouncing on my radio from 3 to 6 bars most of the time and so I said I was getting you about S5 or so.
If you are working HF, CW or AM the signal strength is more important and so they are very interested in the actual strength. On FM that's not quite as meaningful, so we just stick to the straight S-scale and say S9 or higher is just full quieting. What that means is that the modulated carrier is sufficiently strong that your radio has no issue demodulating your voice from the signal, so you get no static or anything, i.e. a fully quiet channel with just information coming out of the speaker.
So for the bulk of us, a contact read back would be a gut readability and simply reading the S-meter on your radio. Oh, BTW, this is really only a simplex thing, giving the signal of a repeater is completely meaningless. You can offer clarity readings (i.e. scratchy or inability to hold the input link) on a repeater contact, but since the repeater is re-transmitting a signal with like 200W from an ideal location, of course you will get S9...
More geeky stuff follows
So if you have a better S-meter you might say 'I'm getting you R,S of 4, 65dB', which means literally that the signal strength at your rig is -65dBm. This is 65dB below standard 0 dBm, which is about 1mW of received power. You might also say you have a contact at '5, 20dB over S9', which means you have a very clear readability and 20dB of additional strength over S9.
To give you a reference, 1mW is about the field strength generated by a wireless mouse or Bluetooth ear piece at 1 meter of distance. So -65dB is 1/1,000,000th (yes, one millionth) of that power. The decibel is 10*log(p1/p2), or for -60dB that's (1000 * 1000) times
less power than the 0dB reference. Each 3dB jump is a reduction or increase in power by 2x...
But
luckily the S scale is already by agreement within the ITU inherently logarithmic and technical already in dB!
For UHF and VHF S9 = -93dBm and each step down is a -6dB jump, so S8 = -99dBm, S7 = -105dBm, etc. For HF S9 is defined as -73dBm. So a VHF S4 would be roughly -123dBm, which is around 0.01pW, that's 1 x 10^-14 watts (picowatts are 10^-12) at your receiver. If you want a comparison, this is considered within the thermal noise (i.e. background noise) for a satellite downlink channel. But yet you still have another dozen or so decibels of S-scale to go...
So that report of 20dB over S9 means on VHF that you are getting a signal strength of -73dBm (-93dB + 20dB over S9 = -73dB). This is a pretty decent signal for ham radio. But if you want a real comparison, -70dBm is roughly the signal strength of WiFi at its fringe and that's considered a super good ham signal!
So at 30
miles or whatever Marco and I had our 25W contact our radios were picking up signals similar in strength to what your laptop might see at 200
feet and we were perfectly clear in our conversation until we went down to 5W of power (which gave us S1~S2 levels, -125dB!). Pretty friggin' amazing radios if this EE says so himself.