Interesting. In looking at the data taken from my Omni VI Plus a couple of
years ago I find that the S meter seemed quite accurate. Feeding the
HP8656A generator to the input of the receiver, 50 uV equals S -9 on the
meter. Then in -6 dB steps down in level, the S-meter tracked +/- needle
width down to S-3. Looking at levels over S-9, I noted that 50 uV +10 dB
indicates 10 over S-9, and 20 dB over 50 uV is 20 over S-9 and 30 dB over 50
uV the meter indicates 30 dB over S-9. This was after the S meter was
calibrated as per the manual. The physical reading of the meter below S-3
was noted as undecernable with regard to accuracy.
I did some repair work on my Collins S-Line 75S-3B and clearly, S-9 = 100 uV
as per the manual. I do notice that the meter scale show S-9 to be 40 on
the DB scale with S-3 at 20 on the DB scale. The difference is 6 S units
and 20 DB. This nets a 3.3 dB per S unit level.
I seem to recall reading some history about the S unit. It was generally
supposed to be a measurement to comply with the RST system.
Still love the reports that go "ur 599 hr, please repeat your QTH and Name
and my RST". sigh
73
Bob, K4TAX
----- Original Message -----
From: "Tony Berg" <tony.w1ot@gmail.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Thursday, January 10, 2008 7:59 AM
Subject: Re: [TenTec] STANDARDISATION OF S-METER READINGS
> In the February 2008 issue of QST, on page 36, there is a reference to
> an internet article on this topic. The web address is not quite right.
> It should be (I hope I get this right):
>
> www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/SMeterBlues.htm
>
> 73, Tony W1OT
>
> On 1/9/08, Jim Brown K9YC <k9yc@audiosystemsgroup.com> wrote:
>> On Tue, 8 Jan 2008 21:15:51 -0600, Bob McGraw - K4TAX wrote:
>>
>> >Fortunately most companies today do adhere to and have adopted the
>> >50 uV for S-9 as the standard and one S unit change is 6 dB signal
>> >change.
>>
>> Really? I doubt it. I own two TS850s and two FT1000MPs. I haven't
>> measured the sensitivity of S9 (I simply didn't pay attention), but
>> I looked at the value of an S-unit. In general, S8 to S9 is usually
>> be 6 dB, but S7 to S8 is less, and S-units below S6 are about 3 dB
>> on a good day. YMMV. Standard adhered to by manufacturers? Ya gotta
>> be kidding.
>>
>> 73,
>>
>> Jim Brown K9YC
>>
>>
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