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Re: Beacon Strength



Jim,
I did a similar exercise on my 736 2 metre module some time
back and they show a similar trend to  your results.
My results are in the RH column. I also noted that above S9
the 20dB values were correct.
It would appear each radio has it own characteristics.
My measurements were made at 145.35 which is where I receive
the 2.4 GHz beacon. I did note that there were variances across
the range 144 to 148 which is why elected to calibrate at 145.35.
I have been an amateur for 40 years and one of my erstwhile
mentors (now a silent key) always refers to S Meters as GUESS
meters. Never forgotten that comments which was made many
years ago when commercial equipment started to become available
and the publicity always included the capabilities of S Meters.
The bottom line. Nothing has changed. HI!!
Colin VK5HI

     "S" units        db change

       1-2            2            1.5
       2-3            2            2.0
       3-4            1            2.5
       4-5            2            2.5
       5-6            2            3.0
       6-7            2            3.5
       7-8            3            5.0
       8-9            5            5.0

----- Original Message -----
From: "Dr. Jim Akers" <jakers@ECE.MsState.EDU>
To: "ALberto Helmfelt" <lu2fgn@yahoo.com.ar>
Cc: "AMSAT-BB" <amsat-bb@AMSAT.Org>
Sent: Thursday, December 13, 2001 4:14 PM
Subject: Re: [amsat-bb] Beacon Strength


> Alberto,Hilton and all,
>
> I guess I may as well throw in my two cents worth.
>
> A number of years ago, one of the HF RX manufacturers tried to standardize
> his receivers with a 6 db increment between "S" units.  There was a lot of
> interest in the ham community at the time.  It never worked out. I think
> for several reasons.  First he couldn't assembly line produce receivers
> that had this quality. Second none of the other manufacturers would go
> along with the idea.  Third there was no real benefit to having such a
> standard.  But the MYTH of 6 db between "S" meter increments was born.  I
> cannot remember which company tried this but Hallicrafters comes to
> mind...but maybe not.
>
> Several years ago, maybe ten or fifteen or so, I measured my HF RX "S"
> meter units to see how it stacked up. This was a TS-440s.  It was no where
> near 6 db per "S" unit.  In fact, it wasn't even constant between units.
> Out of curiosity, I decided to measure the 2m section of the FT-736R I was
> using on AO-13.  It was no where near 6 db and it was not linear either.
> About a year or so ago, in an idle moment, I decided to repeat these
> measurements on the same FT-736.  They were essentially the same as
> several years ago.  I have not tried this on either the 70 cm or the 1.2
> Ghz modules in the 736 but I would suspect I would get different results
> on each one.  In fact, I suspect that I could measure two 736 on 2 m and
> get different results.  Unless you measure your own "S" meter and know
> what the increments mean, comparisons are just not valid.
>
> Here are the results of my measurements.
>
>     "S" units        db change
>
>       1-2            2
>       2-3            2
>       3-4            1
>       4-5            2
>       5-6            2
>       6-7            2
>       7-8            3
>       8-9            5
>
> I find this useful now to determine when I am approximately 10 db below
> the beacon.
>
> 73 and Merry Christmas to all.
>
> Jim...W5VZF.
>
>
>
>
> Dr. Jim Akers
> Dept. of Electrical
> and Computer Engineering
> Miss. State Univ.
>
>
> On Thu, 13 Dec 2001, ALberto Helmfelt wrote:
>
> > Hi Hilton..
> >
> > Your right, One S unit equals 3 db this is doubled power this is the
> > reasong for this relation.
> > Also I have the same values for noise flor and max beacon S7, my antenna
> > 1,6 mtrs and DEMI with squint around 3/5 if there was a biger dish the
> > signal diference will bee grater.
> >
> > Best Regards.
> >
> > Alberto LU2FGN
> >
> >
> >
> > At 01:23 p.m. 13/12/01 +1300, you wrote:
> > >For some time I have been observing what would appear to be somewhat
> > >extravagant claims for the strength of the AO40 Beacon. It is my
> > >understanding that the best level the Beacon can reach above the noise
> > >floor is perhaps 27 or 28 dB.  Another source measured this as around
21dB.
> > >My question is how can claims be made for S9+ levels when the standard
S
> > >point unit is 6dB?   I would suggest that a more realistic level claim
> > >would be dB above the noise floor if this can be determined. With my
modest
> > >set-up using an FT847 with attenuator on, pre-amp off and noise floor
at
> > >under S1 on the meter, the beacon at best reaches S7.  Signals that
don't
> > >upset Leila are around S4 or 5 which in IMHO would equate to 12 or 15
dB
> > >above the noise floor.  The S unit on the FT847 would seem to be 3dB?
> > >Regardless of the size of the antenna if you can detect the noise floor
you
> > >have reached the practical limit of signal level?  I would appreciate
some
> > >input from more learned persons on this, thank you.
> > >Hilton Meyer  ZL2MN
> > >
> > >
> > >----
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> > >
> >
> >
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>
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