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Re: DB'S per s-units on 847



Ed,

Looks like your values agree nicely with mine at an approximate 3 dB per
S-Unit. Thanks for the data above S6!

I just did some crude sun noise measurements using TRX-Meter and my 847. It
has a scale of dBm for doing antenna plots. I pointed the antenna at the
sun, took 9 noise samples ...then moved it to a quiet spot and took 9 more
samples. Each "sample" is actually several mini-samples, representing,
perhaps five or ten samples averaged for each "sample"...this value is then
reported by the program.

This is what I got:

(125 AZ, 34 EL)

At Sun   Away from Sun (dBm)
-95        -104
-96        -103
-96        -104
-95        -104
-95        -104
-95        -103
-95        -104
-95        -103
-95        -104
-95        -103

Looks like 8 to 9 dB of Sun Noise...although this is a very crude method.
The one thing that is nice, is I"m seeing clear sun noise, whatever it's
absolute value. The results are quite repeatable.

HyperLink Tech 39" BBQ, UEK-3000, 80' LMR-400, FT-847 Internal Preamp ON.

73

(I have a nice *.bmp of the plot that I can make into a jpeg if you want a
copy, Ed)

hasan schiers, N0AN

schiers@netins.net
or use amsat.org or arrl.net remailer
----- Original Message -----
From: "Edward R. Cole" <al7eb@ptialaska.net>
To: <amsat-bb@AMSAT.Org>
Sent: Wednesday, September 19, 2001 9:41 AM
Subject: Re: [amsat-bb] DB'S per s-units on 847


> >From: "Luc Leblanc (VE2DWE)" <luclebla@sorel-tracy.qc.ca>
> >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)
>
> Luc,
>
> Back in June I asked myself the same question and so calibrated my FT-847
> with an IFR-500 service monitor thru a 23 dB attenuator from S-1 to S-9:
>
> FT-847 state: internal preamp-ON, DSP-OFF, USB-mode, AGC-slow
> -153.0 dBm produced a trace on AO40.RCV and I consider the MDS*
> -114.5 S-1
> -113.0 S-2
> -111.0 S-3
> -109.0 S-3.5
> -108.0 S-4
> -107.0 S-4.5
> -103.0 S-5
> -101.0 S-6
> -98.0  S-7
> -88.0 S-9
>
> As you can see it is a very inconsistent and non-linear curve.  I plan to
> repeat this for both internal preamp-ON/OFF.  Also I can take the radio to
> work and repeat this using an IFR-120 which has better resolution of
output
> signal [0.1 dB vs. 0.5 dB].  I could also compare this with an external
> step attenuator, but they have only 1 dB steps.  {but in truth it is hard
> to resolve less than a half s-unit on the FT-847 s-meter}
>
> I generalize and say that the meter runs about 3dB/s-unit.  Obviously that
> is a gross oversimplification.
>
> *From memory, the internal preamp adds approx. 15 to 20 dB gain, so MDS
> without the preamp on is loosly about -133 dBm {Yaesu claims sensitivity
> -122 dBm}.  In fact my ears need another ten dB so I guess they agree with
> Yaesu {but probably means personally I need an S/N of 10 dB to hear a
signal}.
>
> Not a lab quality test, but that's what I found.
> Ed
>
> Ed
>
> ----
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>

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