Unfortunately the S-meter reference plane is not the antenna connector,
but the AGC voltage at a convenient, but unstated set of conditions re
attenuator, preamp, frequency, etc. The key word here is "convenient"
not 'accurate' or 'consistent'. In this regard, ORION is better than
some in that an effort is made to calibrate S9 (under unspecified
conditions) to a consistent 50 microvolts (per Collins) and to maintain
a 6 decibel S-unit interval under those same conditions.
The comments about requiring information about antenna gain and line
loss are correct, but beyond the knowledge and means of most amateurs to
specify accurately.
Why is S-meter accuracy not better, you ask? Not much demand for a
measurement which is generally regarded as subjective rather than
scientific. Most amateur radio receivers are not intended as measuring
instruments for RF power, frequency, and bandwidth. A competitive
marketplace mitigates against a higher level of measurement than is
necessary to pursue a hobby.
Hope this helps....
73, Allan, W1AEL, Sevierville, Tennessee.
orion-request@contesting.com wrote:
Send Orion mailing list submissions to
orion@contesting.com
To subscribe or unsubscribe via the World Wide Web, visit
http://lists.contesting.com/mailman/listinfo/orion
or, via email, send a message with subject or body 'help' to
orion-request@contesting.com
You can reach the person managing the list at
orion-owner@contesting.com
When replying, please edit your Subject line so it is more specific
than "Re: Contents of Orion digest..."
Today's Topics:
1. S meter (Martin Ewing)
2. RE: S meter (Richard Detweiler)
----------------------------------------------------------------------
Date: Mon, 29 Mar 2004 16:08:55 -0500
From: Martin Ewing <martin@aa6e.net>
To: orion@contesting.com
Subject: [Orion] S meter
Message-ID: <40689067.8010909@aa6e.net>
Content-Type: text/plain; charset=us-ascii; format=flowed
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Precedence: list
Message: 1
The discussion about S meter calibration reminds me of a question I have for all
the grey beards out there.
If S9 = 50 uV is standard, and 6 dB per S unit (or is it 5 dB?), my question is
what is the "reference plane" for the measurement?
The useful reference, to me, should be the input connector. If that were true,
the S meter reading should NOT CHANGE when switching the preamp on or off or
changing the attenuator. This is clearly not the case with the Orion - or with
many (all?) rigs I've used.
Except for history, we would be better served by power measurements -- "Your
sigs today are -120 dBm, old man". Or maybe, "Your sig is 10 dB above my noise
level."
Accurate S readings (or power for that matter) aren't very meaningful if you
don't know the antenna/feed line gain/loss. Frequently I am getting 589 or 599
when my Orion's meter shows S4 for the other guy.
Oh well, it's a hobby!
73, Martin AA6E
p.s. Nice S meter stuff at http://www.geocities.com/ja1vbn2000/etc/S-unit.html
------------------------------
Date: Mon, 29 Mar 2004 15:32:20 -0600
From: "Richard Detweiler" <rdetweil@hotmail.com>
To: orion@contesting.com
Subject: RE: [Orion] S meter
Message-ID: <BAY1-F1650DYWutQxl500011817@hotmail.com>
Content-Type: text/plain; format=flowed
MIME-Version: 1.0
Precedence: list
Message: 2
Hi Martin,
To add to the confusion, When Aligning the S-Meter, I find the S-Meter is
only calibrated for a particular frequency as well.
Usually 20 Meters about 14.250
I often wonder if the S-meter has any real meaning of units as it can be off
by alot from radio to radio and from frequency to frequency.
They all seem to have about the same gain needed to move up one S unit of
6db though.
Lets see, to go from S3 to S5 is a 12db gain, so, if the transmitter was at
100 Watts out at S3, then be Transmitter would have to be 1600 watts out
to make S5.
73's
Rich
K5SF
From: Martin Ewing <martin@aa6e.net>
To: orion@contesting.com
Subject: [Orion] S meter
Date: Mon, 29 Mar 2004 16:08:55 -0500
The discussion about S meter calibration reminds me of a question I have
for all the grey beards out there.
If S9 = 50 uV is standard, and 6 dB per S unit (or is it 5 dB?), my
question is what is the "reference plane" for the measurement?
The useful reference, to me, should be the input connector. If that were
true, the S meter reading should NOT CHANGE when switching the preamp on or
off or changing the attenuator. This is clearly not the case with the
Orion - or with many (all?) rigs I've used.
Except for history, we would be better served by power measurements --
"Your sigs today are -120 dBm, old man". Or maybe, "Your sig is 10 dB
above my noise level."
Accurate S readings (or power for that matter) aren't very meaningful if
you don't know the antenna/feed line gain/loss. Frequently I am getting
589 or 599 when my Orion's meter shows S4 for the other guy.
Oh well, it's a hobby!
73, Martin AA6E
p.s. Nice S meter stuff at
http://www.geocities.com/ja1vbn2000/etc/S-unit.html
_______________________________________________
Orion mailing list
Orion@contesting.com
http://lists.contesting.com/mailman/listinfo/orion
_________________________________________________________________
Check out MSN PC Safety & Security to help ensure your PC is protected and
safe. http://specials.msn.com/msn/security.asp
------------------------------
_______________________________________________
Orion mailing list
Orion@contesting.com
http://lists.contesting.com/mailman/listinfo/orion
End of Orion Digest, Vol 6, Issue 18
************************************
_______________________________________________
Orion mailing list
Orion@contesting.com
http://lists.contesting.com/mailman/listinfo/orion
|