K3/P3 issue

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K3/P3 issue

NK7Z
Perhaps I missed the answer to this...

My SVGA external monitor shows signals about 1/2 to one S unit lower
than my P3 does on the native screen...  What am I missing?

If I use Peak Hold, there is a clear 1/2 to one S-Unit difference in teh
display height...
--
Thanks and 73's,
For equipment, and software setups and reviews see:
www.nk7z.net

For MixW support see;
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For Dopplergram information see:
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For MM-SSTV see:
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Re: K3/P3 issue

Paul Saffren N6HZ
Hi David,

Check your inbox/spam folder, I emailed you directly on this.  

-Paul
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Re: K3/P3 issue

NK7Z
Nothing, but THANK YOU...  Can you remail me please...
--
Thanks and 73's,
For equipment, and software setups and reviews see:
www.nk7z.net

For MixW support see;
http://groups.yahoo.com/neo/groups/mixw/info
For Dopplergram information see:
http://groups.yahoo.com/neo/groups/dopplergram/info
For MM-SSTV see:
http://groups.yahoo.com/neo/groups/MM-SSTV/info


On Thu, 2015-10-01 at 13:36 -0700, Paul Saffren N6HZ wrote:

> Hi David,
>
> Check your inbox/spam folder, I emailed you directly on this.  
>
> -Paul
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/K3-P3-issue-tp7608605p7608606.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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Re: K3/P3 issue

Alan Bloom
In reply to this post by NK7Z
For a continuous CW tone, the level should be the same on the P3 and the
external monitor.  For SSB, the SVGA display should read 1/2 S-unit lower.

The reason is that, unlike CW, an SSB signal is spread out in frequency.
  Since the SVGA monitor has twice the frequency resolution than the P3
main screen, each display point only covers half the bandwidth.  So you
would expect it to read 3 dB lower (half the power), which is half an S
unit.

Alan N1AL


On 10/01/2015 01:11 PM, David Cole wrote:
> Perhaps I missed the answer to this...
>
> My SVGA external monitor shows signals about 1/2 to one S unit lower
> than my P3 does on the native screen...  What am I missing?
>
> If I use Peak Hold, there is a clear 1/2 to one S-Unit difference in teh
> display height...
>
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Re: K3/P3 issue

David Pratt
In a recent message, Alan <[hidden email]> writes
>So you would expect it to read 3 dB lower (half the power), which is
>half an S unit.

This is something that has always puzzled me, Alan. I agree that -3dB is
half the power (in watts), but S-meter calibration is related to
(micro)voltage.   It is often assumed that doubling ones power increases
the signal at the receiving end by one S-point.  But what is the
technical explanation of this?

73

David G4DMP

--
  + - - - - - - - - - - - - - - - - +
  | David M Pratt, Kippax, Leeds.   |
  | Website: http://www.g4dmp.co.uk |
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Re: K3/P3 issue

Guy Olinger K2AV
3 dB?

I've seen an S unit described as 6 dB -- double the *voltage*, or four
times the power. Or in recent years some radios do 5 dB -- keep a linear
string of LED's where over S9 is in 5 dB increments and below S9 is in 5 dB
S units.

Your assertion is the first time I have ever heard an S unit described as 3
dB.

But to be truthful, there is no metric system authority that sets an S
unit. There are recomendations from radio organizations, all stating 6 dB.
To see S units way back in the beginning, here is a photo of the front of a
1936 RME-69 receiver.

http://www.virhistory.com/ham/spkrs/RME_007.jpg

If you look at the meter labeled "Carrier Level Indicator," below the scale
marks you will see S1 through S9. Above the scale marks you will see dB,
originally spelled DB, from 0 to 72, in 6 dB steps. The S1 through S9 use
the same marks as 0 through 48 on the dB scale. S1=0dB, S2=6dB, ...
S9=48dB. Very clearly S units on this pre-WW2 classic radio are 6 dB.

This predates a 1939 National HRO receiver manual that explains S-units as
6 dB.

So history says S units are 6 dB, with each S unit a doubling of the
voltage of the prior S unit.

An earlier version of the signal strength meter on the RME-69 was
calibrated in dB on one side of the scale and microvolts on the other,
without S units.

Most S meters are notoriously inaccurate and might not tell you any more
than signal A is louder than signal B. Whether the RME-69 could function as
a frequency selective microvolt meter with a decent degree of accuracy is
anyone's guess. I suspect that they could not make the old tube circuits
and the manufacturing tolerances actually match a microvolt scale across
manufactured units, and so they went relative with S units.

Everything you never wanted to know about an S-unit.   :>)

73, Guy K2AV



On Fri, Oct 2, 2015 at 2:43 AM, David G4DMP <[hidden email]> wrote:

> In a recent message, Alan <[hidden email]> writes
>
>> So you would expect it to read 3 dB lower (half the power), which is half
>> an S unit.
>>
>
> This is something that has always puzzled me, Alan. I agree that -3dB is
> half the power (in watts), but S-meter calibration is related to
> (micro)voltage.   It is often assumed that doubling ones power increases
> the signal at the receiving end by one S-point.  But what is the technical
> explanation of this?
>
> 73
>
> David G4DMP
>
> --
>  + - - - - - - - - - - - - - - - - +
>  | David M Pratt, Kippax, Leeds.   |
>  | Website: http://www.g4dmp.co.uk |
>  + - - - - - - - - - - - - - - - - +
>
> ______________________________________________________________
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>
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