In message , Roy Lewallen
writes
Sal M. Onella wrote:
I've heard the same thing, but the reality is that the S-meter
usually
follows the AGC and the signal for S9 could be different for every design.
But Flex radio and others define S9 as 50 uV. . .

Adjusting the S-meter to read a specific value for one signal strength
is simple, and there's often an adjustment for doing it. I think it's
fairly common to find S9 to be around 50 uV -- on one band at least --
although I wouldn't be surprised to see a fair amount of variation from
band to band. But that has nothing to do with what the difference is
between S7 and S8, S8 and S9, etc.

Isn't there a school of thought which says that, above 1000MHz, an
S-point is 3dB? [Don't ask me why!]
--
Ian

In article ,
Ian Jackson wrote:

In message , Roy Lewallen
writes
Sal M. Onella wrote:
I've heard the same thing, but the reality is that the S-meter
usually
follows the AGC and the signal for S9 could be different for every design.
But Flex radio and others define S9 as 50 uV. . .

Adjusting the S-meter to read a specific value for one signal strength
is simple, and there's often an adjustment for doing it. I think it's
fairly common to find S9 to be around 50 uV -- on one band at least --
although I wouldn't be surprised to see a fair amount of variation from
band to band. But that has nothing to do with what the difference is
between S7 and S8, S8 and S9, etc.

Isn't there a school of thought which says that, above 1000MHz, an
S-point is 3dB? [Don't ask me why!]

there are "Many Schools of thought".... but unless someone rewrites the
Laws of Physics, and increase in Tx Output will show and Increase of Rx
Input, on the same path, period. S-meters are NOT necessarily actually
showing Rx Receive Signal Strength, and they are rarely, either linear,
or even Logrythmnic in presentation of what they do represent. In the
Microwave Field if you measure a path, and also calculate that path,
comparing the two will show that they are very close, if you did it
right....

In message , You
writes
In article ,
Ian Jackson wrote:

In message , Roy Lewallen
writes
Sal M. Onella wrote:
I've heard the same thing, but the reality is that the S-meter
usually
follows the AGC and the signal for S9 could be different for every design.
But Flex radio and others define S9 as 50 uV. . .

Adjusting the S-meter to read a specific value for one signal strength
is simple, and there's often an adjustment for doing it. I think it's
fairly common to find S9 to be around 50 uV -- on one band at least --
although I wouldn't be surprised to see a fair amount of variation from
band to band. But that has nothing to do with what the difference is
between S7 and S8, S8 and S9, etc.

Isn't there a school of thought which says that, above 1000MHz, an
S-point is 3dB? [Don't ask me why!]

there are "Many Schools of thought".... but unless someone rewrites the
Laws of Physics, and increase in Tx Output will show and Increase of Rx
Input, on the same path, period.

I'm not sure what statement you are arguing against. Has anyone said
otherwise?

S-meters are NOT necessarily actually
showing Rx Receive Signal Strength

So what DO they 'show'? OK, they may not 'show' it very accurately, and
the way they work is usually a very indirect way of 'measuring' the
signal power or voltage at the receiver input, but I'm sure that this is
what the do 'show'.

For convenience, most S-meters use the AGC voltage to provide an
indication of incoming signal level. However, some FM-only CB sets have
no AGC, and have to pick off an input level dependent voltage from
somewhere else in the circuit. These are usually VERY inaccurate. What
alternative methods do you suggest?

, and they are rarely, either linear

No one is disagreeing. S-meters are renowned liars. Mind you, I have a
CB set (which has an AGC line) which is converted to 10m, and this has
an S-meter which has remarkably consistent 6dB S-points between S2 and
S9 +20dB.
,
or even Logrythmnic

No one's disagreeing.

in presentation of what they do represent. In the
Microwave Field if you measure a path, and also calculate that path,
comparing the two will show that they are very close, if you did it
right....

You are undoubtedly correct. But did anyone say that this was not the
case?
--
Ian

No one is disagreeing. S-meters are renowned liars. Mind you, I have a CB set
(which has an AGC line) which is converted to 10m, and this has an S-meter
which has remarkably consistent 6dB S-points between S2 and S9 +20dB.

Even considering an ideal S-meter having a perfect one-S point-per-6 dB
response, the answer to the original question is that only in theory doubling
the transmit power turns into a 3-dB increase in S-meter reading.

In practice what the S-meter "measures" is the sum of the "wanted" signal power,
plus the background noise power (which on e.g. 160 meters could be quite high),
plus possibly the power other signals falling in the receiver bandwidth. If the
wanted signal is not strong enough to overwhelm al other contributions, doubling
the transmit power will not turn into a 3-db S-meter reading increase.

73

Tony I0JX, Rome Italy


:

If we double the power
radiated by an antenna (+3 dB), how does it translate on the S-meter
at a receiver 'far' away..

On Wed, 22 Jul 2009 18:34:46 +0200, "Antonio Vernucci"
wrote:

Even considering an ideal S-meter ... If the
wanted signal is not strong enough to overwhelm al other contributions, doubling
the transmit power will not turn into a 3-db S-meter reading increase.

It would have to. Any additional power to the general spectrum is
going to raise the power in the spectrum - even if you cannot
distinguish it. That is, afterall, how the spectrum gets to become so
noisy. If you are tuned to the radiator that has gone through a power
boost, then your S-Meter should indicate it.

73's
Richard Clark, KB7QHC

Even considering an ideal S-meter ... If the
wanted signal is not strong enough to overwhelm al other contributions,
doubling
the transmit power will not turn into a 3-db S-meter reading increase.

It would have to. Any additional power to the general spectrum is
going to raise the power in the spectrum - even if you cannot
distinguish it. That is, afterall, how the spectrum gets to become so
noisy. If you are tuned to the radiator that has gone through a power
boost, then your S-Meter should indicate it.

73's
Richard Clark, KB7QHC

Yes, but not quite 3dB when transmit power is doubled. A 3-dB increase would
only occur if the "wanted" signal would be alone in the receiver bandwidth (viz
no background noise, no interfering signal).

73

Tony I0JX

On Wed, 22 Jul 2009 19:35:40 +0200, "Antonio Vernucci"
wrote:

Yes, but not quite 3dB when transmit power is doubled.

It would be dependent upon S+N/N, yes.

73's
Richard Clark, KB7QHC