Is there a standard RF input level per "S" Unit?

If so, please post the location. Thanks.

"Avery Fineman" wrote in message
...
Is there a standard RF input level per "S" Unit?

If so, please post the location. Thanks.


There is no "standard". You will often see it mentioned as 6 db of power
per S-unit. At one time 50 microvolts into the receiver was S-9 and you
went down 6 db of power per S-unit from there. I doubt that any receiver
will follow that so called "standard".

The rule voor 50µV = S9 does still exists, this is voor HF, @50 Ohm input
impedance at receiver.
"They" (radioamateurs) use another rule for VHF.
It's in the software MultiCalc, Google will find the adres, it's for free.
Official or not, if everyone use this rule then it is a standard for me.
Greetings Bas.


"Avery Fineman" schreef in bericht
...
Is there a standard RF input level per "S" Unit?

If so, please post the location. Thanks.

I find that most of them seem to sort of follow the rule that 4uV is S9, 3dB
down is each S-Point, that's for VHF/UHF.

Sam

"bviel" wrote in message
...
The rule voor 50µV = S9 does still exists, this is voor HF, @50 Ohm input
impedance at receiver.
"They" (radioamateurs) use another rule for VHF.
It's in the software MultiCalc, Google will find the adres, it's for free.
Official or not, if everyone use this rule then it is a standard for me.
Greetings Bas.


"Avery Fineman" schreef in bericht
...
Is there a standard RF input level per "S" Unit?

If so, please post the location. Thanks.






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Avery Fineman wrote:
Is there a standard RF input level per "S" Unit?

If so, please post the location. Thanks.

There is an IARU recommendation, which originated in Region1
(Europe/Africa) and I believe has been adopted by IARU world-wide.

The Region 1 recommendation is:
http://www.algonet.se/~k-jarl/ssa/IARU/smeter.html
Google should also bring up the full technical paper behind this, and
probably the current IARU recommendation. ISTR there's something on the
ARRL website too.

The 1990 Region 1 recommendation simply states that:

STANDARDISATION OF S-METER READINGS
1. One S-unit corresponds to a signal level difference of 6 dB,

2. On the bands below 30 MHz a meter deviation of S-9 corresponds to an
available power of -73 dBm from a continuous wave signal generator
connected to the receiver input terminals,

3. On the bands above 144 MHz this available power shall be -93 dBm,

4. The metering system shall be based on quasi-peak detection with an
attack time of 10 msec +/- 2 msec and a decay time constant of at least
500 msec.


IARU functions very much like an
Entmoot...only...not...quite...so...hoom...hasty. In 2004, they are just
starting to think about the gap between 30MHz and 144MHz:
http://home.hccnet.nl/a.dogterom/Vie...4_19_Chair.rtf


But all the other comments about S-meters are true as well: that no
S-meter actually conforms to this recommendation; that it makes no
practical difference; and that hardly anyone cares.

There's a very good web page with lots of practical measurements, at:
http://www.seed-solutions.com/gregor...rimentation/SM
eterBlues.htm


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

If you're wondering if S-meters are calibrated to some standard, the
answer is that they're not. S-meters simply read the AGC voltage, which
is only approximately logarithmic. Therefore, the number of dB per S
unit typically varies from one part of the scale to another. For
example, the S-meter in my Icom 730, on 40 meters, preamp off, varies
from 1.3 to 4.0 dB per S-unit depending on where on the scale you are.
The "10 dB" increments over S-9 vary from 5.6 to 13.5 dB. Receiver
manufacturers are free to make the sensitivity whatever they want, and
seldom exceed about 5 dB per S-unit, because users complain that the
meter is too "Scotch" (insensitive) if they do.

There is a tendency for receivers to be calibrated to about 50
microvolts at one point on the meter, S-9, and there's often a
calibration adjustment for this.

Any "standard" is useless at best and misleading at worst, because it
bears no relation to what S-meters really read.

Roy Lewallen, W7EL

Avery Fineman wrote:
Is there a standard RF input level per "S" Unit?

If so, please post the location. Thanks.

On Fri, 26 Nov 2004 05:56:42 +0100, "bviel" wrote:

The rule voor 50µV = S9 does still exists, this is voor HF, @50 Ohm input
impedance at receiver.
"They" (radioamateurs) use another rule for VHF.
It's in the software MultiCalc, Google will find the adres, it's for free.
Official or not, if everyone use this rule then it is a standard for me.
Greetings Bas.


"Avery Fineman" schreef in bericht
...
Is there a standard RF input level per "S" Unit?

If so, please post the location. Thanks.




On HF there is no need for an S-meter standard because it seems to be
the rule to give report 59. If you don't you soon have a bad
reputation of giving wrong reports

I installed an MC3356 log detector and calibrated it for S9 = 50uV.
For about 15 years there has never been any signal of S9+30dB, most
reports should be around 539....579, but again you logging problems,
because everybody expect 599 and some log programs don't include the
reports, they are supposed to be 599

73
Jan-Martin
LA8AK (ex-G5BFV)
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm

"Avery Fineman" wrote in message
...
Is there a standard RF input level per "S" Unit?

If so, please post the location. Thanks.


My homebrew solid state receiver (see QRZ.COM) uses 5 dB per S-unit. S9
corresponds to -73 dBm available power, which is 100 microvolts open-circuit
from a 50 ohm sig gen, or 50 microvolts into a 50 ohm load. Available power
and open-circuit voltage are used because the input inpedance of the
receiver is not guaranteed to be 50 ohms. I use 5 dB per S unit because it
compresses the scale a little and it also agrees more closely with the
intuitive listening test measure that I have used for many years. The upper
end of the scale is 30 dB above S9, which is -43 dBm, a very strong signal.
Signals stronger than S9+30 dB I don't bother to measure. At S1 the signal
level is -73 - 40 = -113 dBm. Signals weaker than that S1 I don't try to
quantify.

My receiver has a low noise RF preamp with 8 dB of gain that I use on the 12
and 10 meter bands, when those bands are quiet. This makes the S meter less
accurate but I don't worry about that. To get an S meter reading I turn off
the preamp briefly.

My receiver has a custom made, computer printed scale using a calibrated sig
gen, and there are two trimpot adjustments, one for the low end and one for
the high end. This circuit uses voltage regulated opamps. The S meter
dynamics are adjusted using RC time constants.

My S meter is accurate within +/- 2 dB from 160 M to 10 M, because the
receiver is designed for this accuracy. Because of the IF and RF circuit
design, the scale calibration is fairly correct and reliable, as I
mentioned.

Bill W0IYH

"William E. Sabin" wrote in message
...

"Avery Fineman" wrote in message
...
Is there a standard RF input level per "S" Unit?

If so, please post the location. Thanks.


My homebrew solid state receiver (see QRZ.COM) uses 5 dB per S-unit. S9
corresponds to -73 dBm available power, which is 100 microvolts
open-circuit from a 50 ohm sig gen, or 50 microvolts into a 50 ohm load.
Available power and open-circuit voltage are used because the input
inpedance of the receiver is not guaranteed to be 50 ohms. I use 5 dB per
S unit because it compresses the scale a little and it also agrees more
closely with the intuitive listening test measure that I have used for
many years. The upper end of the scale is 30 dB above S9, which is -43
dBm, a very strong signal. Signals stronger than S9+30 dB I don't bother
to measure. At S1 the signal level is -73 - 40 = -113 dBm. Signals weaker
than that S1 I don't try to quantify.

My receiver has a low noise RF preamp with 8 dB of gain that I use on the
12 and 10 meter bands, when those bands are quiet. This makes the S meter
less accurate but I don't worry about that. To get an S meter reading I
turn off the preamp briefly.

My receiver has a custom made, computer printed scale using a calibrated
sig gen, and there are two trimpot adjustments, one for the low end and
one for the high end. This circuit uses voltage regulated opamps. The S
meter dynamics are adjusted using RC time constants.

My S meter is accurate within +/- 2 dB from 160 M to 10 M, because the
receiver is designed for this accuracy. Because of the IF and RF circuit
design, the scale calibration is fairly correct and reliable, as I
mentioned.

Bill W0IYH


My receiver also has a 20 dB antenna input attenuator that can be switched
in from the front panel. This extends the upper signal range to S9 + 50 dB.
I use it very rarely.

Bill W0IYH

On HF there is no need for an S-meter standard because it seems to be
the rule to give report 59. If you don't you soon have a bad
reputation of giving wrong reports

A signal doesn't have to be S9 to be heard 5 by 9.
I would usually tell the guy on the other end what
the S meter read, and also how readable he was.
When the band is quiet QRN wise, I could honestly
give a 59 report to someone hardly moving the meter.
OTOH with heavy QRM+QRN someone could be pumping
30db over and still be a rough copy.