db relation TX/RX
 

www.qsl.net/k5lxp/projects/SMeter/SMeter.html

Check the chart to see actual input readings. I've always used the (6db per
S unit) as a general rule-of-thumb.

db relation TX/RX
 

Rollie wrote:
.. . .I've always used the (6db per
S unit) as a general rule-of-thumb.

Which is fine if you don't mind possibly being off by a factor of 50 or
more, mistaking the gain of a 3 element beam for the gain of a 150
element one. Or you might only be off by a factor of 10, thinking the 3
element beam only has the gain of a 30 element beam. Shucks, what's a
few dB anyway.

Roy Lewallen, W7EL

db relation TX/RX
 

On Jul 19, 5:36*am, Roy Lewallen wrote:
Rollie wrote:

. . .I've always used the (6db per

S unit) as a general rule-of-thumb.

Which is fine if you don't mind possibly being off by a factor of 50 or
more, mistaking the gain of a 3 element beam for the gain of a 150
element one. Or you might only be off by a factor of 10, thinking the 3
element beam only has the gain of a 30 element beam. Shucks, what's a
few dB anyway.

Roy Lewallen, W7EL

All of my radios are at least 15 years old before DSP. I was wondering
manufactureres that had gone to DSP were using it to make S meter
indications more accurate. I am seeing this type of signal correction
being made in some of the equipment that I work on that has gone to
DSP.

Jimmie

db relation TX/RX
 

On Sun, 19 Jul 2009 03:00:51 -0500, "Rollie"
wrote:

www.qsl.net/k5lxp/projects/SMeter/SMeter.html

Check the chart to see actual input readings. I've always used the (6db per
S unit) as a general rule-of-thumb.

More receiver S-meter testing:
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/SMeterBlues.htm#
http://www.smeter.net/slc/signal/strengths.php




--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

db relation TX/RX
 

Thanks for the references.

Where does the fiction come from that an "S-unit", presumably the marks
on our S-meters, is or for some reason should be, 6 dB -- that this is a
"correct" or "ideal" value? To me it's the same as "defining" pi to be
3.2, as the Indiana House of Representatives once did. "Defining" an
S-unit to be some value has no effect on our S-meters, any more than the
proposed Indiana law changed the ratio of the circumference to diameter
of a circle.

Roy Lewallen, W7EL

Jeff Liebermann wrote:
On Sun, 19 Jul 2009 03:00:51 -0500, "Rollie"
wrote:

www.qsl.net/k5lxp/projects/SMeter/SMeter.html

Check the chart to see actual input readings. I've always used the (6db per
S unit) as a general rule-of-thumb.

More receiver S-meter testing:
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/SMeterBlues.htm#
http://www.smeter.net/slc/signal/strengths.php

db relation TX/RX
 

On Sun, 19 Jul 2009 12:20:40 -0700, Roy Lewallen
wrote:

Thanks for the references.

One more (in German):
http://www.s-meter.de
This one is rather interesting in that you can use the site to make an
S-meter scale.

Software to convert a perfectly good digital receiver data output,
into marginally useful S-Units:
http://www.seed-solutions.com/gregordy/Software/SMeterLite.htm

Where does the fiction come from that an "S-unit", presumably the marks
on our S-meters, is or for some reason should be, 6 dB -- that this is a
"correct" or "ideal" value?

Using S-Units is its own punishment. I couldn't find anything on the
history of the S-Meter that would substantiate my guess that long ago
some major radio company incorporated a signal meter into their
receiver. Soon after, everyone had to have one. Whether they did
anything useful is probably debatable. I guess it's not considered a
proper ham radio unless it has an S-meter. For example, the new
Elecraft K3 now has a software S-Meter for those that just can't live
without one:
http://www.sight.net/K3Meter/

My guess(tm) is that the 6dB per S-Unit was probably fairly close for
the early tube type receivers. Below S-9 was probably below the AGC
threshold. Above S-9 was more compressed above the knee in the AGC
curve. AGC thresholds in old tube radios was probably a fairly strong
signal, mostly because the RF/IF chain didn't have much gain. 6dB per
S-Unit was probably fairly close and fairly linear below the AGC
threshold.

Roll forward 90 years and we have sensitive receivers that have an AGC
knee at a few dB above the noise floor, with lots of overload handling
ability to maintain a wide AGC range, and sensitivities much better
than tube radios. If I maintain my assertion that S9 is the AGC knee,
there would be perhaps one or two S-Units below S9, and the rest of
the scale would be highly compressed "dB over S9" units. That would
be a rather strange looking S-Meter, but might also be more useful
than the current dual range meter.

I'll give cellular designers minimal credit for replacing the
inaccurate S-Meter with a less accurate 5 bar graph. Not satisfied
with the bar graph abomination, they also invented that rather
non-linear RSSI indication, and then cut it in half again by using
0-100 instead of 0-255.

I suspect that in the future, when we're all carrying FTL sub-space
communicators, Tricorders, and direct thought transmission radios, the
associated projection or heads up display will probably include an
S-Meter.

To me it's the same as "defining" pi to be
3.2, as the Indiana House of Representatives once did. "Defining" an
S-unit to be some value has no effect on our S-meters, any more than the
proposed Indiana law changed the ratio of the circumference to diameter
of a circle.

So it is written, so it must be.

Actually, I didn't think of it much until you mentioned it, but
6dB/S-Unit is rather improbable. The base line noise level for an
antique AM radio is probably about 10uv which I presume is S1. S9 is
loosely defined as 50uv. 6dB per S-unit implies a:
9*6 = 54dB
range, which is considerably larger than the:
20 log (50/10) = 14dB
range.

If the 14dB range from S1 to S9 were considered the basis for
calibration, then:
14dB / 9 S-Units = 1.5dB per S-Unit
nowhere close to 6dB per S-Unit

Or, if 6dB per S-unit, and S9=50uv are considered sacred, then 54dB
below 50uv (-72dBm) =
-72dBm -45dBm = -117dBm = 0.3uv, which is rather improbable.
However, that will work for a modern receiver, with fairly good front
end sensitivity and gain.

Roy Lewallen, W7EL

Jeff Liebermann wrote:
On Sun, 19 Jul 2009 03:00:51 -0500, "Rollie"
wrote:

www.qsl.net/k5lxp/projects/SMeter/SMeter.html

Check the chart to see actual input readings. I've always used the (6db per
S unit) as a general rule-of-thumb.

More receiver S-meter testing:
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/SMeterBlues.htm#
http://www.smeter.net/slc/signal/strengths.php



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

db relation TX/RX
 

"Rollie" wrote in message
...
www.qsl.net/k5lxp/projects/SMeter/SMeter.html

Check the chart to see actual input readings. I've always used the (6db
per
S unit) as a general rule-of-thumb.



The chart is interesting. Where the "S-Meter Standard" numbers come from,
in blue on the left? If I were to create such an "S-Meter Standard" chart
myself without source or authentication, I might be inclined to set S-9
equal to -73 dBm/50 uV and extend the S-values down from there at the
popular rate of 6 dB per S-unit.

Chart values do decrease at 6 dB per S-unit but the chart sets -72 dBm/56.8
uV as S-9, vice 73 dBm, 50 uV. 1 dB isn't much to quibble about, but it
does make me inquire about the source of the data.

Can anyone elaborate? TKS

BTW, http://en.wikipedia.org/wiki/S_meter provides a similar chart based
around 73 dBm as S-9. It sources IARU Region 1 Technical Recommendation
R.1. I looked for it; no luck.

Sal

db relation TX/RX
 

"Roy Lewallen" wrote in message
...
Thanks for the references.

Where does the fiction come from that an "S-unit", presumably the marks
on our S-meters, is or for some reason should be, 6 dB -- that this is a
"correct" or "ideal" value?


Might be IARU Region 1 Technical Recommendation R.1. See
http://www.algonet.se/~k-jarl/ssa/IARU/smeter.html

Do we have to adhere to it? No, but if enough equipment makers implemented
it, we might have a tough time ignoring it.

Sal

db relation TX/RX
 

"Sal M. Onella" wrote in
:

....
Chart values do decrease at 6 dB per S-unit but the chart sets -72
dBm/56.8 uV as S-9, vice 73 dBm, 50 uV. 1 dB isn't much to quibble
about, but it does make me inquire about the source of the data.

Actually, it is 146dB lower than that... 50µV in 50 ohms is -73dBm.

Owen

db relation TX/RX
 

"Owen Duffy" wrote in message
...
"Sal M. Onella" wrote in
:

...
Chart values do decrease at 6 dB per S-unit but the chart sets -72
dBm/56.8 uV as S-9, vice 73 dBm, 50 uV. 1 dB isn't much to quibble
about, but it does make me inquire about the source of the data.

Actually, it is 146dB lower than that... 50µV in 50 ohms is -73dBm.

Owen

Yeah, I missed a minus sign there, didn't I? Good catch.
Here it is: -

Sal

db relation TX/RX
 

"Sal M. Onella" wrote in message
...

"Owen Duffy" wrote in message
...
"Sal M. Onella" wrote in
:

...
Chart values do decrease at 6 dB per S-unit but the chart sets -72
dBm/56.8 uV as S-9, vice 73 dBm, 50 uV. 1 dB isn't much to quibble
about, but it does make me inquire about the source of the data.

Actually, it is 146dB lower than that... 50µV in 50 ohms is -73dBm.

Owen

Yeah, I missed a minus sign there, didn't I? Good catch.
Here it is: -

Sal

I seem to recall that the KWM-2a was calibrated for 100uv for s9. 1db is
well within the resolution of a lot of lab gear. 50uv would be more
appropriate for a modern radio that should be that much hotter. The RST
system of reporting was supposed to be a relative thing anyway.

db relation TX/RX
 

Hello,

Roy, with all the respect i owe you, you are barking up the wrong tree.
1 S-point should be 6 dB. Manufacturers choose not to do this for
obvious cost reasons. Yet this is the definition, and they should work
on it, especially so now, with digital techniques.
Remains the definition of S9, supposedly different on HF & VHF. I am not
so sure about this, but strongly support HF S9 = 50 uV.

Thanks for your enlightening comments on this newsgroup.

Olivier, HB9CEM / AE7AL





Roy Lewallen wrote:
Thanks for the references.

Where does the fiction come from that an "S-unit", presumably the marks
on our S-meters, is or for some reason should be, 6 dB -- that this is a
"correct" or "ideal" value? To me it's the same as "defining" pi to be
3.2, as the Indiana House of Representatives once did. "Defining" an
S-unit to be some value has no effect on our S-meters, any more than the
proposed Indiana law changed the ratio of the circumference to diameter
of a circle.

Roy Lewallen, W7EL

Jeff Liebermann wrote:
On Sun, 19 Jul 2009 03:00:51 -0500, "Rollie"
wrote:

www.qsl.net/k5lxp/projects/SMeter/SMeter.html

Check the chart to see actual input readings. I've always used the
(6db per S unit) as a general rule-of-thumb.

More receiver S-meter testing:
http://www.seed-solutions.com/gregordy/Amateur%20Radio/Experimentation/SMeterBlues.htm#

http://www.smeter.net/slc/signal/strengths.php