++++++++++++++++++ Reply-To: From: "John Lucas" To: "Elecraft" Date: Mon, 7 Apr 2003 19:31:18 -0400 Subject: [Elecraft] K2 S Meter Could someone plese explain the correct use of the S meter. To this rooky it seems I can give any signal any S reading by changing the RF gain! thanks John va3jsl at rac.ca ++++++++++++++++ From: "Stuart Rohre" To: , "Elecraft" Subject: Re: [Elecraft] K2 S Meter Date: Mon, 7 Apr 2003 18:38:28 -0500 That is the way most S meters work. They are monitoring the Automatic Volume Control feedback voltage, which has maximum effect at maximum RF gain. See the ARRL web site Technical Information Service for FAQs like this. 73, Stuart K5KVH ++++++++++++++++ From: "W8TIF - Karl" To: , "Elecraft" Date: Mon, 7 Apr 2003 18:49:24 -0500 Subject: [Elecraft] Re: K2 S Meter Dear Rookie (correct spelling), The best "correct" useage of the "S-Meter" (on any rig, not just the K2) is "Don't Look At It!" In CW mode, the "S" (signal strength) report is totally subjective by you, the listener, not the "S-Meter". In fact, the same thing applies when you're operating in the SSB voice mode. Signal strength reports are (and should be) totally subjective -- that is: how do you perceive the signal to be? Karl K - W8TIF McKinney, Texas ----- Original Message ----- From: "John Lucas" To: "Elecraft" Sent: Monday, April 07, 2003 6:31 PM Subject: [Elecraft] K2 S Meter > Could someone plese explain the correct use of the S meter. > > To this rooky it seems I can give any signal any S reading by changing the > RF gain! > > thanks > John > va3jsl at rac.ca > ++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: , "'Elecraft'" Subject: RE: [Elecraft] K2 S Meter Date: Mon, 7 Apr 2003 17:01:06 -0700 Ha!!! Your observation is right on, John! All the S-meter is doing is = monitoring the automatic gain control voltage that does electrically what your RF = gain knob does manually.=20 Indeed, back in the 1930's when "S" meters were just starting to show up = on the most expensive receivers, some manufacturers "calibrated" the gain control in "S" units. You set the gain for a comfortable listening level = and looked at the number under the pointer on the knob to determine the "S" reading. Just what you can do with the K2 by looking at the bar graph as = you discovered. The "S" from RST was, of course, part of a "by the ear" system of = evaluating the other station's signal. The RST system caught on among Hams in the 1920's as they struggled to reduce key clicks, yoops and chirps, and tinkered with better power supplies to get the AC hum on their signals = down to something that at least sounded "musical". A 1-5 scale for = "Readability" was borrowed from the commercial "QSA" code in which a signal is = reported by a single digit from 1 to 5 with the "5" being "armchair copy". S for signal Strength and T for Tone were given 9 possible values, indicating about the range of changes that an ops ear could discern. But, just as today, us "techno-nuts" were fascinated by numeric readouts = and "graphical displays". Only in 1930 those were wiggling meters on = calibrated scales, not digital displays and computer screens. As soon as superheterodyne receivers started using AGC to manage the gain, someone caught the idea of measuring the AGC voltage and the S-meter was born = and became a rather useless but absolutely indispensable part of any REAL = Ham receiver.=20 So, at best, an "S" meter is a way to noticing if the other guy's signal = is changing up or down... assuming you can't hear it changing. VERY roughly speaking, an "S" unit is about 6 dB or a 4:1 power change. That is, if = you up your power from 5 to 20 watts, your signal will have increased about = 1 "S" unit at the receiving end. Go from 20 to 80 watts and it'll be = another "S" unit stronger.=20 At it's worst, it's used to decide what the other op's "S" report should = be no matter what you ears tell you. In any case, it's a part of Ham Radio history that few ops want to do without.=20 If you want to start a real argument among Hams, just ask how an "S = meter" should be calibrated!! Once they were included in manufactured = receivers, the manufacturers had to decide how to adjust them to make sure the = receiver worked when it left the factory. Various manufacturers adopted various standards, and those arbitrary standards have become law to some Hams.=20 Me, I set my K2 S-meter by tuning in an "average" signal, deciding that = it was about S-7 by ear, then I adjusted the S-meter to say S-7. Now the S-meter and I agree so I don't have to look at it any longer.=20 But, you know something? If my S-meter quit working, I'd probably fix = it. After all I am a Ham. Ron AC7AC K2 # 1289 +++++++++++++++++ From: "George, W5YR" To: , , "'Elecraft'" Subject: Re: [Elecraft] K2 S Meter Date: Mon, 7 Apr 2003 23:49:34 -0500 Organization: W5YR Ron, you may have another radio in mind, but the earliest one I recall with a calibrated gain control was the little regen made by National in the 30's. Incidentally, the numerals on that one were termed "R" units since in those days prior to the RST system, signal strength was informally reported on an R1 to R9 scale, which is how the dial of the gain control knob was calibrated. Sorry I don't recall the model number or name of the National but it was something like the SW-3. I believe that it had two tubes, a regen detector and one stage of audio. As a side note, now that our super receivers have such excellent multi-loop AGC systems, one finds it very difficult to tell much about the strength of a signal by how much sound it makes. The audio output may vary on a few dB at most for a 100-dB change in signal level at the antenna terminals. Maybe that is why the default "599" signal report obtained on all contest contacts is as good and as meaningful as any when most signals all sound about the same loudness. 73/72, George Amateur Radio W5YR - the Yellow Rose of Texas Fairview, TX 30 mi NE of Dallas in Collin county EM13QE "In the 57th year and it just keeps getting better!" +++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: "'Elecraft'" Subject: RE: [Elecraft] K2 S Meter Date: Mon, 7 Apr 2003 22:57:11 -0700 You are right George!! The little National Regen did is the one I was thinking of... and now = that you mention it, it did have an "R" scale on the volume control. You made = me go "look" and you were even right on the model number: SW-3. Now we know who is the REAL resident "Old Timer" around here! Hi! You are right about AGC reducing the change in the audio level so signal changes aren't so obvious as they used to be. I like to play a game of deciding how strong the signal is by ear then checking the meter to see = if we agree. We do more often than not!=20 I operate with the AGC off a lot too...I like the fact that when = there's no signal in the passband the noise stays down in volume instead of having = the AGC bring it up loud when there's a pause in the signal.=20 The place where I really appreciate AGC is in round tables or nets where signal strengths vary a lot.=20 Ron AC7AC K2 #1289 +++++++++++++++++++ From: "Rick Dettinger" To: Date: Tue, 8 Apr 2003 11:53:47 -0700 Subject: [Elecraft] K2 S meter The S meter not only changes with the setting of the RF gain control, it = also changes when the preamp is turned on. With the preamp on, the S = meter reads about 2 S units higher. =20 The S meter is most useful for relative measurements, such as comparing = antennas. This can be done on receive as "normal" antennas have = reciprocal properties on transmit and receive. Also, due to this reciprocity, the S meter readings for two stations in = contact should only very according to the power difference. The = antennas cancel out as long as the same antennas are used for transmit = and receive. This is true even if one station is using a large array = and the other is using a dummey load! Therefor, if you think the other = op is giving you a "polite" report, you can determine what it should be = by adjusting your S meter reading for the difference in power levels. = If you are using 5 watts and he is using 100 watts and your S meter = reads S7 then you know that your signal is approx. S5. 73, = K7MW ++++++++++++++++++