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

Tue Mar 30 16:09:30 EST 2004

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 at contesting.com wrote:
> Send Orion mailing list submissions to
> 	orion at 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 at contesting.com
> 
> You can reach the person managing the list at
> 	orion-owner at 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 at aa6e.net>
> To: orion at contesting.com
> Subject: [Orion] S meter
> Message-ID: <40689067.8010909 at 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 at hotmail.com>
> To: orion at contesting.com
> Subject: RE: [Orion] S meter
> Message-ID: <BAY1-F1650DYWutQxl500011817 at 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 at aa6e.net>
>>To: orion at 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 at 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 at contesting.com
> http://lists.contesting.com/mailman/listinfo/orion
> 
> 
> End of Orion Digest, Vol 6, Issue 18
> ************************************
> 