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Re: DB'S per s-units on 847



Lue,

It depends on a LOT of things and making generalizations is going to be very
iffy. There are variations among modes, and variations between different
847's, is the 847 internal preamp ON or OFF? All of these things will impact
any informaton anyone provides to you. So, it's not going to be easy to
answer your question...at least with any sense of accuracy.

I can give you a "ballpark" figure for some of it, but I sure wouldn't put
ANY FAITH IN IT AT ALL. I'll put a calibrated attenuator in line and give
you some readings, but the "real" solution is to buy a calibrated attenuator
yourself and do the measurements on your own radio. MFJ makes a cheap step
attenuator that is very useful. That is what I'm going to use to produce the
readings below:

I could only start with a max signal of S6 with noise from my downconverter
and the internal RF amp in the 847 ON. Maybe I can get a higher reading
pointing at the sun later today.

S-Meter Change      dB Used     dB per S-Unit

S6 > S5                   3 dB            3 dB
S5 > S4                   6 dB            3 dB
S4 > S3                   9 dB            3 dB
S3 > S2                  12 dB          3 dB
S2 > S1                  14 dB          2 dB
S1 > S0                  17 dB          3 dB

S0 = last dot on S-meter flickers about 50% of time.
Conclusions:

1. Surprisingly linear at about 3 dB per S-Unit from S1 to S6.

2. This means NOTHING from S6 and above. There is no reason whatever to
believe that this 3 dB per S-Unit will hold from S6 to S7, much less from S7
to S8 and S8 to S9. DON'T MAKE THIS MISTAKE!

3. Notice that the 847 only has numbers at 1,3,5.7,9...interpolating the
even numbers in between is another source of obvious error. (Although I used
a separate program TRX-Meter to read my S-Meter digitally to the computer
from the 847, both in uV and dBm). Eye-balling the S-meter was much more
accurate than I had thought it might be.

The answer to your question?

On my radio on 2m USB with RF amp on: about 3 dB per S-Unit from S6 down to
S0.

hasan schiers, N0AN

schiers@netins.net
or use amsat.org or arrl.net remailer
----- Original Message -----
From: "Luc Leblanc (VE2DWE)" <luclebla@sorel-tracy.qc.ca>
To: <amsat-bb@AMSAT.Org>
Sent: Wednesday, September 19, 2001 4:33 AM
Subject: [amsat-bb] DB'S per s-units on 847


>
>
> Anyone knows how many DB'S per S-UNITS the 847 meter has been factory
calibrated under S9 mark?
>
> Thank's
>
> Luc Leblanc VE2DWE (AMSAT 33583)
> SITE WEB:http://www.sorel-tracy.qc.ca/~luclebla/
> C.P.341
> Sorel
> J3P 5N6
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

----
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