[Elecraft] K3S DSP Filter Plots

[Ron D'Eau Claire]

Some receivers in use back when Art Collins decided on what S-9 meant (I'm
recalling some National products) simply calibrated the volume control in
S-units. One adjusted the volume for a good listening level and read the
S-unit reading off of where the volume control pointed!

The impetus for Collins was very pragmatic. Production test techs on the
assembly line needed a specific reference to determine that the receiver and
S-meter were working as expected. That meant an S-number corresponding to a
certain RF level at the antenna input. 

My point is that there was nothing "sacred" about that decision. And keep in
mind that back then the High Frequencies (H.F.) stopped at 30 MHz. Anything
above 30 MHz, including the 10 meter Amateur band, was officially Ultra High
Frequency (UHF). All the focus of most Hams was on H.F. 

But most Hams simply gave signal reports based on how the signal sounded.
Personally I have always appreciated the QSA system we used on commercial
radiotelegraph circuits: QSA 5 was very good and QSA 1 a barely perceptible
signal. 

73, Ron AC7AC

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bob
McGraw - K4TAX
Sent: Wednesday, November 18, 2015 3:46 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] K3S DSP Filter Plots

The original S meter development for HF radios was done by Art Collins.  
At that time the number used was 100 uV for S-9 to coincide with the RST
system.  Later the value was revised to 50 uV for S-9.  Values above S -
9 are stated usually in dB although I've seen some in microvolts.  If one
ventures into the VHF spectrum then the value changes.  {I forget to what
value}

73
Bob, K4TAX

On 11/18/2015 3:31 PM, Fred Jensen wrote:
> I believe there's more than one correct answer.  In earlier times, the 
> "Collins Standard" was 6 dB/S-unit and 50 uv = S9.  My 75S3 came in at
> 53 uv for S9, and pretty much held to the 6 dB/S-unit below that.  Not 
> so much above S9


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