Does this Hellp ? Re: [Yaesu] FT-1000(X) S-meter calibration

[WD8ARZ]

After reviewing the FT1000MP Service manual, I can provide the following
information about what Yaesu calibration procedure directs.

On page 3-1 in a note it says: Signal levels in dB referred to in alignment
are based on 0 dBu=0.5uv.

On page 3-8 it says for S-meter full scale: Connect the RF signal generator
to the antenna jack, and inject a +100dBu signal. Tune for peak indication
on the S-meter. Adjust VR2002 for S9+60dB on the S-meter.

There are earlier steps for setting the S-meter segments to just being off,
and just being full scale for minimum and maximum settings of the rf gain
control. Rf and if stages have also been calibrated prior to the S-meter.

If this information is valid (main manual is dated august of 95, but I am
sure some updates have occured on some of the pages), then unless I am
missing something, full scale is 100dB for +60dB over S9.

With just a 40 foot peice of wire, I have seen +60dB over S9 on some
shortware stations. Such as on 5.070 Mhz out of Nashville Tn. If a FT1000MP
is always reading too low on the S-meter, and there is not a rig problem,
then it needs to be calabrated. Also note that some of the calibration for
this radio is part of the hidden 9-x menu options. Making changes to those
settings will affect calibration and must be done correctly with elaborate
calibrated test equipment.

Band noise on 80 meters most nights routinely hold the s-meter over S9. If
anything on my rig, I find the receivers to be hot and quite often have the
IPO off and a attenuater value switched in. (this improves audio quality on
strong signals and the signal to noise ratio)

Hope this helps.

73 from Bill Stamps - WD8ARZ
E-Mail Reply to:
wd8arz@null.net

----------
> From: peca@galeb.etf.bg.ac.yu
> To: yaesu@contesting.com; 1000mp-list@jehosophat.com
> Subject: Re: [Yaesu] FT-1000(X) S-meter calibration
> Date: Monday, November 10, 1997 10:21 AM
> 
> Tyler Stewart wrote:
> > 
> > The MP is full scale at S9 + 60 DB, which Yaesu sets for +100dbu.  
> > That would make S9 a +40dbu, which tranlates to 50 microvolts 
> > on a 50 ohm sig. gen.
> > 
> 
> 	Could someone please explain this ????
> It is my job to know things about dBu, dBm, uV, etc, but this conversion
> is totally unclear to me!
> 
> Isn't it dBu = 20log(U/1uV) ?
> where:
> U is expressed in volts, 
> 1uV is what it looks like it is:) and
> 'log' is a base ten logarythm.
> 
> So, 50uV/1uV = 50 -> 20log(50) = 33.979dBuV
> And +40dBuV would be:   10^(40dBuV/20)*(1uV) = 10^2 = 100uV
> If you write it down on paper it's much more clear.
> And for power it's dBmW = 10log(P/1mW)
> 
> Hmm...unless you mean dBuW when you say dBu ? (which almost sure doesn't
> fit into my definition, too :)
> 
> 73 de YT1ZKB
> zoran
> kn04ft


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