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[Orion] Re: Orion Digest, Vol 6, Issue 18

To: orion@contesting.com
Subject: [Orion] Re: Orion Digest, Vol 6, Issue 18
From: Allan Henry Kaplan <w1ael@mindspring.com>
Date: Tue, 30 Mar 2004 16:09:30 -0500
List-post: <mailto:orion@contesting.com>
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.


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Today's Topics:


   1. S meter (Martin Ewing)
   2. RE: S meter (Richard Detweiler)


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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>
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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>
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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

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End of Orion Digest, Vol 6, Issue 18 ************************************



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