You make a good argument, Bill. It's important to note that the S-unit is a subjective "by-ear" evaluation of a signal strength.
When someone manufactures a product, it's important to know how to determine if it was assembled and working as expected. It was for those reasons that various manufacturers came up with ways of adjusting the receiver to produce certain readings on the "S-Meter" when test signals of certain levels were applied to the input. The only historically (and in practice correct) measurement is to listen to the signal by ear and judge the "S-reading". If the meter doesn't agree with what you decided by listening to the signal without referring to the meter, the meter is wrong. Ron AC7AC -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bill W5WVO Sent: Wednesday, June 06, 2007 6:39 PM To: [Elecraft] Subject: [Elecraft] K3: S-meter calibration (redux) To recap: In a thread on this list back when the K3 was first announced, there was a good deal of debate about how many dB an S-unit should be on a calibrated S-meter. It was pointed out that if an S-unit is 6 dB, then a signal at the receiver noise floor would be between S1 and S2 on the meter, which seems rather high; a 5-dB S-unit, for example, would put the noise floor a lot closer to where it intuitively belongs on the meter. But it was also pointed out that the 6-dB S-unit has very deep historical roots, and in IARU Region 2, it's a published spec, not a matter of endless debate. All this discussion was based on the universal assumption that S9 is by definition hard-pegged at 50 uV. It was the one assumption no one questioned. Today, ARRL Labs' review of the new TenTec OMNI VII was published on their website (members only), and it was revealed that the OMNI VII S-meter is in fact accurately calibrated at 6 dB per S-unit -- but that S9 is pegged at 67 uV, not 50 uV! Using this higher threshold for S9 and a 6-dB S-unit, the noise floor drops down to where it should be -- somewhere between S0 and S1. A 10 dB S+N/N signal of 0.5 uV comes in around an intuitively reasonable S2. To me, this seems like an elegant and creative solution to the "6-dB problem," drawing a sensible compromise between tradition and engineering common sense. It will be interesting to see where the K3 comes down in all this. There seems little doubt that the K3 and the OMNI VII (in that order, #1 and #2) are going to dominate the "center" of the transceiver market for a long time. By all rights, IKenSu should be completely shut out once both the K3 and the OMNI VIII are in the marketplace. They will have to depend on marketing hype and brand loyalty -- but who knows, that may be enough to keep them in the game until they can catch up. IF they can catch up. :-) Bill / W5WVO _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
