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Re: [TenTec] Orion (original) S-meter

To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Subject: Re: [TenTec] Orion (original) S-meter
From: "Ron Castro" <ronc@sonic.net>
Reply-to: Ron Castro <ronc@sonic.net>,Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sat, 18 Feb 2006 12:39:02 -0800
List-post: <mailto:tentec@contesting.com>
True enough about S-meters historically being a relative indication.  There 
was a time in late 50's and early 60's when the "S-meter wars" started 
between the manufacturers, mostly Hallicrafters and Hammerlund.  On each 
successive model, they boosted the sensitivity so that if you did a 
side-by-side comparison, the radio showing the highest reading would be 
thought to be superior. The strategy worked for a while, until everybody got 

I  think that was about the time that the S-9 = uV, and 6 dB per S-unit 
standard got popular, and Collins stuck to it pretty rigorously.  They are 
still known as having "Scotch" (as in 'tight-fisted') meters.

Obviously readings are relative since a receiver hooked to a dipole at 10' 
will read far less than one connected to a 6 over 6 over 6 array on a 180' 
tower.  The benefit of accurately calibrated meters are to help in antenna 
comparisons, getting a "ball-park" on F/B ratios, relative conditions 
between stations that talk on a regular basis (I do that on 75 all the 
time), comparing two stations in nearby locations, etc.  Both my KWM-380 and 
my TS-870 have S-meters that are remarkably accurate, although I determined 
that the '380 uses a 5-dB/S-unit standard instead of 6.  The 870 has a 
menu-selectable option that automatically changes the S-meter reading to 
compensate for the preamp.

It would be nice to have readings that correlate to a known standard in the 


----- Original Message ----- 
From: "Lin Davis" <linbdavis@earthlink.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, February 18, 2006 11:16 AM
Subject: Re: [TenTec] Orion (original) S-meter

> Just a note about S-Meters. From what I've read it was only
> ever intended as a relative signal strength indication,
> meaning that from one receiver type to the next, there is no
> correlation. It looks like rig vendors are at least starting
> to calibrate them at one point, S9/50uV. Traditionally, the
> actual measurement was of the AGC voltage. How this voltage
> tracks signal input level is completely dependent on the
> gain control characteristics of the rf/if amplifiers
> involved, so it is highly variable. So I don't believe it
> makes sense to say that +10 over S9 means 10dB over S9, etc.
> But now that we have software running our s-meters, it is
> possible to display a calibrated signal level measurement,
> taking preamps and attenuation into account, with the scale
> in dBm or dBuV, rather than S units. Unfortunately, I don't
> think this would be an easy thing for manufactures to
> do. Each rig would need to be calibrated independently,
> given the component variations from unit to unit.
> ... ramblings from this engineer :)
> 73,
> Lin
> -----------------------------------------------------------
> Ron Castro wrote:
> > Whoops...I didn't mean for it to come out like that!  Lets try this...
> >
> Reformatted:
> Orion II S-Meter Readings from Ron Castro, N6AHA
> from E-mail rcvd February 18, 2006
> Standard  Standard   Orion II  Pre off  Orion II  Pre on
> S-Units   uV    dBm  pre off   Descrep  Pre on    Descrep
>   S-5    3.16   -97    S-2     -12 dB    S-6       6 dB
>   S-7    12.57  -85    S-5     -12 dB    S-9       12 dB
>   S-9    50     -73    +5        5 dB    +30       30 dB
>   +10    158    -63    +25      15 dB    +42       32 dB
>   +20    500    -53    +40      20 dB    +55       35 dB
>   +30    1583   -43    +52      22 dB    +60       30 dB
>   +40    5006   -33    +62      22 dB  Off Scale    N/A
>   +50    15830  -23 Off Scale    N/A   Off Scale    N/A
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