S-Meter Measurement

What is my S-Meter telling me?

I've often read how inaccurate S-meters are on most modern HF transceivers. I took the opportunity to test some Icom HF rigs, a 746Pro, 735, 706 and a 756ProII. Below is a table showing the S-meter value, what the levels should be in both microvolts and dBm, and the measured value for each radio. Turns out the 735 and 756ProII tracks the S-meter standard above S-7 pretty closely, but other than that they're all over the map!

<>Check out W7GT's similar review of the Yaesu FT-1000 S-Meter: Web or Archive

S-Meter Measurements
S-Meter Standard			IC-746Pro			IC-735			IC-706			756ProII
Value	uV	dBm	uV	dBm	Delta	uV	dBm	Delta	uV	dBm	Delta	uV	dBm	Delta
MDS*	-	-	.062	-131	-	.06	-131	-	.07	-130	-	.097	-130	-
S1	.2236	-120	5.49	-92	-28	3.20	-97	-23	2.19	-101	-19	2.82	-98	-22
S3	.8902	-108	11.0	-86	-22	6.10	-91	-17	2.48	-99	-9	5.07	-92.9	-15.1
S5	3.544	-96	25.4	-79	-17	12.2	-85	-11	3.35	-96	0	9.12	-87.8	-8.2
S7	14.11	-84	54.3	-72	-12	27.0	-78	-6	11.4	-86	+2	19.1	-81.4	-2.6
S9	56.18	-72	108	-66	-6	76.0	-69	-3	43.6	-74	+2	54.1	-72.2	-.2
S9+10	177.6	-62	495	-53	-9	240	-59	-3	76.7	-69	+6	155	-63.2	+1.2
S9+20	561.8	-52	1.60mV	-41	-11	912	-47	-5	133	-64	+12	549	-52.2	+.2
S9+30	1.776mV	-42	4.42mV	-34	-8	1.95mV	-41	-1	227	-60	+18	1.55mV	-43.2	+1.2
S9+40	5.619mV	-32	11.4mV	-26	-6	4.79mV	-33	+1	398	-55	+23	5.69mV	-31.9	-.1
S9+50	17.76mV	-22	28.8mV	-18	-4	13.8mV	-25	+3	776	-49	+27	17.0mV	-22.4	+.4
S9+60	56.18mV	-12	66.8mV	-10	-2	49.0mV	-13	+1	2.04	-39	+27	53.7mV	-12.4	+.4

*MDS- Minimum Discernable Signal

Tests done using my Rohde and Swartz model SMS 2 synthesized signal generator, F=14.200MHz.
Preamps and attenuators not engaged. Mode=SSB, max bandwidth selected.

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