SB-301 S-meter question

[Edward Swynar]

Hi Glen,

I strongly suspect, too, that far too many CW operators derive the "S"
numeral in their "RST" reports directly from their S-meters...

Many is the time I've copied near-locals on the low bands with 599 signals,
& all I'd ever got back from them was RST 559 (as in S-5 on the meter)...!
It makes no sense --- unless you look at the S-meter, first...

~73~ Eddy VE3CUI - VE3XZ


***************************
----- Original Message -----
From: "Glen Zook" <gzook at yahoo.com>
To: <HEATH at LISTS.TEMPE.GOV>
Sent: Tuesday, March 10, 2009 2:35 PM
Subject: Re: SB-301 S-meter question


> You need to check the "S" meter reading with a well calibrated signal
generator.  It should read S-9 for a 50 microvolt signal.  Now if you are
comparing the reading with a "modern" receiver/transceiver you will often
find that those receivers/transceivers are "way off" in terms of the "olde
fashioned" S-9 = 50 microvolt standard.  I have seen "modern" equipment that
S-9 happens at under 10 microvolts and a "60 over" reading at less than 100
microvolts.  When 50 microvolts is the standard for S-9 then it takes 500
microvolts for a "20 over", 5,000 microvolts for a "40 over", and 50,000
microvolts for a "60 over" reading.
>
> Way too many amateur radio operators these days are so used to getting "20
over" or better readings and they are insulted when someone is using a
receiver that has a well calibrated "S" meter.  Actually, the "S" meter
reading is basically meaningless, it is the signal to noise ratio of the
signal that determines how well it can be copied.  A signal that isn't even
moving the "S" meter but with little or no noise is much easier copied than
a signal that is reading "20 over" and the noise is "19 over".
>
> Glen, K9STH
>
> Website:  http://k9sth.com
>
>
> --- On Tue, 3/10/09, Fred Wittman <wittfa19 at EARTHLINK.NET> wrote:
>
> I've been tinkering with the S-meter on my SB-301 due to weakness.  I
found and replaced one out-of-spec resistor (R104-33k) and it came back to
life.  However, it still seems stingy compared to my other rigs.  I noticed
that the zero set pot actually adjusts the cathode current in V7, a 6BA6.
So here's the question.  What actually effects the sensitivity of the
S-meter?  The meter circuit itself reads the secondary grid of V6 (at the
low end of T3).  FYI, V6 and V7 both test within spec on my NRI model 69
(basic go/no-go tester), and the overall sensitivity  of the receiver is
excellent.  Any ideas?  Thanks in advance.
>
>
>
>
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