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• ## Re: [olivia] new crest factor figures - new MT63 test

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• ... The symbols in Olivia are shaped. See http://homepage.sunrise.ch/mysunrise/jalocha/mfsk_spec.html -- Tomi Manninen / OH2BNS / KP20JF74
Message 1 of 25 , Mar 15, 2005
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On Tue, 2005-03-15 at 16:18, Mark Miller wrote:

> Question for the group: Why does Olivia have a 7.22 dB crest factor?

The symbols in Olivia are shaped. See

http://homepage.sunrise.ch/mysunrise/jalocha/mfsk_spec.html

--
Tomi Manninen / OH2BNS / KP20JF74
• ... True, but not *that* much shaping... Here are my numbers: mfsk_tx random.dat random.mfsk sox -t raw -sw -r8000 random.mfsk -t wav /dev/null stat Maximum
Message 1 of 25 , Mar 15, 2005
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Tomi Manninen wrote:
> On Tue, 2005-03-15 at 16:18, Mark Miller wrote:
>
>
>>Question for the group: Why does Olivia have a 7.22 dB crest factor?
>
>
> The symbols in Olivia are shaped. See
>
> http://homepage.sunrise.ch/mysunrise/jalocha/mfsk_spec.html
>

True, but not *that* much shaping...

Here are my numbers:

mfsk_tx random.dat random.mfsk

sox -t raw -sw -r8000 random.mfsk -t wav /dev/null stat

Maximum amplitude: 0.538757
Minimum amplitude: -0.538757
Midline amplitude: 0.000000
Mean amplitude: 0.000000
RMS amplitude: 0.329407

.538757 / .329407 = 1.63522

20 log (1.63522) = 4.27 dB ... which needs
to be dropped by 3 dB since we're comparing an RMS
voltage to an instantaneous peak (rather than the RMS
value of the signal at the peak).

That puts it down to about a 1.63 dB crest factor...

e.g. if you're running 50 watts RMS output, your
PEP will be 67 watts... which seems reasonable for
what I've experienced.
• ... I used the meter and scope method and came up with 1.56 dB, pretty close isn t it Paul. I have posted the oscilloscope picture at:
Message 1 of 25 , Mar 15, 2005
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At 05:28 PM 3/15/2005, you wrote:
>That puts it down to about a 1.63 dB crest factor...

I used the meter and scope method and came up with 1.56 dB, pretty close
isn't it Paul. I have posted the oscilloscope picture at:

http://home.comcast.net/~mdmiller7/crest_factor/olivia_peak.jpg

73,

Mark N5RFX
• ... Jose, I agree. When I use FSK I don t see any crest factor. When I use AFSK with MixW I do see a very small envelope. 73, Mark N5RFX
Message 1 of 25 , Mar 15, 2005
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At 11:13 AM 3/15/2005, you wrote:
>There SHOULD BE no difference with FSK, if you are
>just shifting frequencies and not doing any amplitude
>modulation. Frequency modulation just shifts energy
>from the carrier to the sidebands, but total energy
>should remain the same.

Jose,

I agree. When I use FSK I don't see any crest factor. When I use AFSK
with MixW I do see a very small envelope.

73,

Mark N5RFX
• ... What do you see if you hook the sound card output up to the scope or other measurement device -- an envelope or just changing frequency? I see varying
Message 1 of 25 , Mar 15, 2005
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Mark Miller wrote:
> I agree. When I use FSK I don't see any crest factor. When I use AFSK
> with MixW I do see a very small envelope.

What do you see if you hook the sound card output up to the 'scope or
other measurement device -- an envelope or just changing frequency?

I see varying output depending on frequency when I run 250 Hz Olivia,
since it puts everything in the 500-1000 Hz audio range going into
the mic jack. Unfortunately, the audio response of my rig isn't flat -
it starts dropping off about 700 Hz or so (although not badly until

73,

-ps
• ... I used the meter and scope method and came up with 1.56 dB, pretty close isn t it Paul. I have posted the oscilloscope picture at:
Message 1 of 25 , Mar 15, 2005
View Source
At 05:28 PM 3/15/2005, you wrote:
>That puts it down to about a 1.63 dB crest factor...

I used the meter and scope method and came up with 1.56 dB, pretty close
isn't it Paul. I have posted the oscilloscope picture at:

http://home.comcast.net/~mdmiller7/crest_factor/olivia_peak.jpg

73,

Mark N5RFX
• ... I see a very tiny envelope. It is so tiny that when I photograph it, it looks like only changing frequency. 73, Mark N5RFX
Message 1 of 25 , Mar 15, 2005
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At 09:10 PM 3/15/2005, you wrote:
>What do you see if you hook the sound card output up to the 'scope or
>other measurement device -- an envelope or just changing frequency?

I see a very tiny envelope. It is so tiny that when I photograph it, it
looks like only changing frequency.

73,

Mark N5RFX
• Tomi I do not agree with your interpretation of the Crest-factor. You will find anywhere that the crest-factor of a pure sinewave is 1.414... -this is the peak
Message 1 of 25 , Mar 16, 2005
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Tomi
I do not agree with your interpretation of the Crest-factor.
You will find anywhere that the crest-factor of a pure sinewave is
1.414...
-this is the peak voltage value, divided by the RMS voltage value

If you keep thinking in terms of voltage values converting to dB
gives 20log1.414 = 3dB
A pure sinewave has a 1.414 or 3dB crest factor...

In practice any modulation will have a crest-factor equal(pure-FSK)
or superior to 3dB...

Now forget about the crest factor and just consider what is
interesting for us: mean to peak power values -both being "average
power values"- (average power being the square of the RMS voltage
- In this case the peak (avg) power is the wattmeter reading when
you "tune" or when you send a RTTY mark
- the mean (avg) power would be a thermical-wattmeter (bolometer)
reading... (a normal wattmeter may indicate anything between mean and
peak depending among other things on the instrument technology...)

I don't have a bolometer, but my conclusion from waveform analysis
(and from temperature elevation of my IC706 !)is that the "mean to
peak" for Olivia is in the 4dB area, which is something similar to
CW... So about 40W with a 100W rated transceiver.

(*)As mentionned in ARRL handbook RMS-power is a mathematical
curiosity whcih has no physical significance. In practice you'll see
everywhere references to RMS-power, but it should be called "average
power" (the product of RMS-voltage by RMS-current). The english
terminology is extremely confusing...

--- In oliviadata@yahoogroups.com, Paul L Schmidt <k9ps@a...> wrote:
> Tomi Manninen wrote:
> > On Tue, 2005-03-15 at 16:18, Mark Miller wrote:
> >
> >
> >>Question for the group: Why does Olivia have a 7.22 dB crest
factor?
> >
> >
> > The symbols in Olivia are shaped. See
> >
> > http://homepage.sunrise.ch/mysunrise/jalocha/mfsk_spec.html
> >
>
> True, but not *that* much shaping...
>
> Here are my numbers:
>
> mfsk_tx random.dat random.mfsk
>
> sox -t raw -sw -r8000 random.mfsk -t wav /dev/null stat
>
> Maximum amplitude: 0.538757
> Minimum amplitude: -0.538757
> Midline amplitude: 0.000000
> Mean amplitude: 0.000000
> RMS amplitude: 0.329407
>
> .538757 / .329407 = 1.63522
>
> 20 log (1.63522) = 4.27 dB ... which needs
> to be dropped by 3 dB since we're comparing an RMS
> voltage to an instantaneous peak (rather than the RMS
> value of the signal at the peak).
>
> That puts it down to about a 1.63 dB crest factor...
>
> e.g. if you're running 50 watts RMS output, your
> PEP will be 67 watts... which seems reasonable for
> what I've experienced.
• Sorry Tomi, this was a reply to Paul s post, not to your... Patrick ... and ... see ... called average
Message 1 of 25 , Mar 16, 2005
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Sorry Tomi, this was a reply to Paul's post, not to your...
Patrick

--- In oliviadata@yahoogroups.com, "Patrick" <f6irf@f...> wrote:
>
> Tomi
> I do not agree with your interpretation of the Crest-factor.
> You will find anywhere that the crest-factor of a pure sinewave is
> 1.414...
> -this is the peak voltage value, divided by the RMS voltage value
>
> If you keep thinking in terms of voltage values converting to dB
> gives 20log1.414 = 3dB
> A pure sinewave has a 1.414 or 3dB crest factor...
>
> In practice any modulation will have a crest-factor equal(pure-FSK)
> or superior to 3dB...
>
> Now forget about the crest factor and just consider what is
> interesting for us: mean to peak power values -both being "average
> power values"- (average power being the square of the RMS voltage
> divided by the load (*))
> - In this case the peak (avg) power is the wattmeter reading when
> you "tune" or when you send a RTTY mark
> - the mean (avg) power would be a thermical-wattmeter (bolometer)
> reading... (a normal wattmeter may indicate anything between mean
and
> peak depending among other things on the instrument technology...)
>
> I don't have a bolometer, but my conclusion from waveform analysis
> (and from temperature elevation of my IC706 !)is that the "mean to
> peak" for Olivia is in the 4dB area, which is something similar to
> CW... So about 40W with a 100W rated transceiver.
>
> (*)As mentionned in ARRL handbook RMS-power is a mathematical
> curiosity whcih has no physical significance. In practice you'll
see
> everywhere references to RMS-power, but it should be
called "average
> power" (the product of RMS-voltage by RMS-current). The english
> terminology is extremely confusing...
>
>
>
>
>
>
>
> --- In oliviadata@yahoogroups.com, Paul L Schmidt <k9ps@a...> wrote:
> > Tomi Manninen wrote:
> > > On Tue, 2005-03-15 at 16:18, Mark Miller wrote:
> > >
> > >
> > >>Question for the group: Why does Olivia have a 7.22 dB crest
> factor?
> > >
> > >
> > > The symbols in Olivia are shaped. See
> > >
> > > http://homepage.sunrise.ch/mysunrise/jalocha/mfsk_spec.html
> > >
> >
> > True, but not *that* much shaping...
> >
> > Here are my numbers:
> >
> > mfsk_tx random.dat random.mfsk
> >
> > sox -t raw -sw -r8000 random.mfsk -t wav /dev/null stat
> >
> > Maximum amplitude: 0.538757
> > Minimum amplitude: -0.538757
> > Midline amplitude: 0.000000
> > Mean amplitude: 0.000000
> > RMS amplitude: 0.329407
> >
> > .538757 / .329407 = 1.63522
> >
> > 20 log (1.63522) = 4.27 dB ... which needs
> > to be dropped by 3 dB since we're comparing an RMS
> > voltage to an instantaneous peak (rather than the RMS
> > value of the signal at the peak).
> >
> > That puts it down to about a 1.63 dB crest factor...
> >
> > e.g. if you're running 50 watts RMS output, your
> > PEP will be 67 watts... which seems reasonable for
> > what I've experienced.
• ... Patrick, Take a look at this article. http://rfdesign.com/mag/radio_crest_factor_analysis/ Toward the bottom of the article you will see two definitions
Message 1 of 25 , Mar 16, 2005
View Source
At 03:13 AM 3/16/2005, you wrote:
>Tomi
>I do not agree with your interpretation of the Crest-factor.
>You will find anywhere that the crest-factor of a pure sinewave is
>1.414...
>-this is the peak voltage value, divided by the RMS voltage value

Patrick,

Take a look at this

Toward the bottom of the article you will see two definitions for crest factor.

Peak crest factor

Next the peak crest factor for the RF signal, W(t), is addressed:

This is the ratio of the instantaneous peak voltage squared to the average
output power, but for translated signals (IF or RF) it is customary to
consider the crest factor for the envelope signal. Because most RF devices
are characterized with sinusoidal signals at either specified or measured
power levels, having the crest factor as a function of a sinusoidal
signal's power level is more appropriate.

Envelope crest factor

To determine the envelope crest factor, first determine the power of a
sinusoidal signal that has the same peak voltage as the modulated signal's
peak voltage. This value is then divided by the average power of the
modulated signal. The result is defined as the translated signal's envelope
crest factor.

Also you will find that peak power does not always mean the peak voltage
squared. Sometimes it means RMS voltage squared. Take a look at the
Alliance for Telecommunications Industry Solutions Web page. It is nicely
laid out.

http://www.atis.org/tg2k/t1g2k.html

crest factor http://www.atis.org/tg2k/_crest_factor.html
peak to average ratio http://www.atis.org/tg2k/_peak-to-average_ratio.html
peak power http://www.atis.org/tg2k/_peak_power_output.html

As you can see peak power is defined as the peak average power.

73,

Mark N5RFX
• ... Yes. I didn t look at the figures that closely. My quick tests with gMFSK and octave seem to agree with your figures. -- Tomi Manninen / OH2BNS / KP20JF74
Message 1 of 25 , Mar 16, 2005
View Source
On Tue, 15 Mar 2005, Paul L Schmidt wrote:

>> The symbols in Olivia are shaped. See
>>
>> http://homepage.sunrise.ch/mysunrise/jalocha/mfsk_spec.html
>
> True, but not *that* much shaping...

Yes. I didn't look at the figures that closely. My quick
tests with gMFSK and octave seem to agree with your figures.

--
Tomi Manninen / OH2BNS / KP20JF74
• Yes Mark, we agree that the terminology is not very clear... http://www.dliengineering.com/downloads/crest%20factor.pdf http://www.tinaja.com/glib/muse125.pdf
Message 1 of 25 , Mar 16, 2005
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Yes Mark, we agree that the terminology is not very clear...

http://www.tinaja.com/glib/muse125.pdf

Even "peak power" may be used to talk about different things (the
debate is as old as SSB - i.e. PEP). Not to mention again the use
(or abuse) of RMS-power... and/or the frequent confusion between
average and mean... (in french we use "puissance efficace" for
average power, and "puissance moyenne" for mean power... which I
think is less confusing)

Why I suggested to forget about the crest-factor, and focus on what
is really interesting for us:

the ratio between
-peak average power (the "tune" wattmeter reading)
-mean average power (the bolometer reading)

What I called "mean to peak" ratio, which is a about 10dB (10%) for
MT63, 6dB (or 25%) for uncompressed-SSB, about 4dB (40%) for CW, and
close to 0dB (100%) for FSK.
The percentage values are often referred as "duty cycle" by equipment
manufacturers, but I also find this appellation a bit confusing...

Patrick

--- In oliviadata@yahoogroups.com, Mark Miller <kramrellim@c...>
wrote:
> At 03:13 AM 3/16/2005, you wrote:
> >Tomi
> >I do not agree with your interpretation of the Crest-factor.
> >You will find anywhere that the crest-factor of a pure sinewave is
> >1.414...
> >-this is the peak voltage value, divided by the RMS voltage value
>
>
> Patrick,
>
> Take a look at this
>
> Toward the bottom of the article you will see two definitions for
crest factor.
>
> Peak crest factor
>
> Next the peak crest factor for the RF signal, W(t), is addressed:
>
> This is the ratio of the instantaneous peak voltage squared to the
average
> output power, but for translated signals (IF or RF) it is customary
to
> consider the crest factor for the envelope signal. Because most RF
devices
> are characterized with sinusoidal signals at either specified or
measured
> power levels, having the crest factor as a function of a sinusoidal
> signal's power level is more appropriate.
>
> Envelope crest factor
>
> To determine the envelope crest factor, first determine the power
of a
> sinusoidal signal that has the same peak voltage as the modulated
signal's
> peak voltage. This value is then divided by the average power of
the
> modulated signal. The result is defined as the translated signal's
envelope
> crest factor.
>
> Also you will find that peak power does not always mean the peak
voltage
> squared. Sometimes it means RMS voltage squared. Take a look at
the
> Alliance for Telecommunications Industry Solutions Web page. It is
nicely
> laid out.
>
> http://www.atis.org/tg2k/t1g2k.html
>
> crest factor http://www.atis.org/tg2k/_crest_factor.html
> peak to average ratio http://www.atis.org/tg2k/_peak-to-
average_ratio.html
> peak power http://www.atis.org/tg2k/_peak_power_output.html
>
> As you can see peak power is defined as the peak average power.
>
> 73,
>
> Mark N5RFX
• As stated before, I m not really concerned with what the ratio is called -- I m concerned that John Q. Ham knows how to adjust his power in order to (a)
Message 1 of 25 , Mar 16, 2005
View Source
As stated before, I'm not really concerned with what the ratio
is called -- I'm concerned that John Q. Ham knows how to adjust
his power in order to (a) transmit cleanly, and (b) not fry his rig.

The term "crest factor" is apparently ambiguous - the definition
that is useful in this case (the one that uses the average power
at the peak of the envelope) is the one that makes sense for the
stated purpose. If everyone understands what is meant by
"crest factor" in this context -- fine. If there is too much
ambiguity, call it PEP to Average ratio. Or the previously-
suggested "SpongeBob's ratio" (anyone else out there have preschool
kids?)

73,

-ps

Patrick wrote:
>
> Sorry Tomi, this was a reply to Paul's post, not to your...
> Patrick
>
> --- In oliviadata@yahoogroups.com, "Patrick" <f6irf@f...> wrote:
>
>>Tomi
>>I do not agree with your interpretation of the Crest-factor.
>>You will find anywhere that the crest-factor of a pure sinewave is
>>1.414...
>>-this is the peak voltage value, divided by the RMS voltage value
>>
>
• ... Patrick, This is a very good article. I have always enjoyed reading Don Lancaster s work. I miss him from the Radio Electronics days. 73, Mark N5RFX
Message 1 of 25 , Mar 16, 2005
View Source
At 04:40 AM 3/16/2005, you wrote:
Patrick,

This is a very good article. I have always enjoyed reading Don Lancaster's
work. I miss him from the Radio Electronics days.

73,

Mark N5RFX
• ... Gotta love it. Pre-school kids! I am a SpongeBob fan too! 73, Mark N5RFX
Message 1 of 25 , Mar 16, 2005
View Source
At 05:09 AM 3/16/2005, you wrote:

>SpongeBob's ratio

Gotta love it. Pre-school kids! I am a SpongeBob fan too!

73,

Mark N5RFX
• ... I was thinking Squidwards clarinet-factor... No, no preschool kids, my son is only 1Â½ years old but that doesn t prevent _me_ from watching SpongeBob. ;)
Message 1 of 25 , Mar 16, 2005
View Source
On Wed, 16 Mar 2005, Paul L Schmidt wrote:

> Or the previously-
> suggested "SpongeBob's ratio" (anyone else out there have preschool
> kids?)

I was thinking Squidwards clarinet-factor... No, no preschool kids,
my son is only 1Â½ years old but that doesn't prevent _me_ from watching
SpongeBob. ;)

--
Tomi Manninen / OH2BNS / KP20JF74
• Paul Looking again at your figures below, at the oscillogram, and at the tone shaping, I would say that you are probably right... Can t explain yet why the
Message 1 of 25 , Mar 16, 2005
View Source
Paul
Looking again at your figures below, at the oscillogram, and at the
tone shaping, I would say that you are probably right...
Can't explain yet why the audio sample I used is giving me such
figures (see in file section) but something is not correct
somewhere... 4.22dB "mean to peak" looks too much...
Looking at it in the frequency domain, I can see that the frequency
response of my audio-sample between 500 and 1500 is not flat but that
the lower frequencies are attenuated by some 8dB, so it is probably
why I am finding this wrong value...

Patrick

PS: the same happened to my first MT63 sample, so I think I did
something wrong when recording...
By the way I would also prefer the tones to be in the 1000-2000 range
rather than 500-1500...

--- In oliviadata@yahoogroups.com, Paul L Schmidt <k9ps@a...> wrote:
> Tomi Manninen wrote:
> > On Tue, 2005-03-15 at 16:18, Mark Miller wrote:
> >
> >
> >>Question for the group: Why does Olivia have a 7.22 dB crest
factor?
> >
> >
> > The symbols in Olivia are shaped. See
> >
> > http://homepage.sunrise.ch/mysunrise/jalocha/mfsk_spec.html
> >
>
> True, but not *that* much shaping...
>
> Here are my numbers:
>
> mfsk_tx random.dat random.mfsk
>
> sox -t raw -sw -r8000 random.mfsk -t wav /dev/null stat
>
> Maximum amplitude: 0.538757
> Minimum amplitude: -0.538757
> Midline amplitude: 0.000000
> Mean amplitude: 0.000000
> RMS amplitude: 0.329407
>
> .538757 / .329407 = 1.63522
>
> 20 log (1.63522) = 4.27 dB ... which needs
> to be dropped by 3 dB since we're comparing an RMS
> voltage to an instantaneous peak (rather than the RMS
> value of the signal at the peak).
>
> That puts it down to about a 1.63 dB crest factor...
>
> e.g. if you're running 50 watts RMS output, your
> PEP will be 67 watts... which seems reasonable for
> what I've experienced.
• I wonder how much of an affect the sound card has on the figures. I use a SoundBlaster Live! and can tell you that its output is not linear and its third
Message 1 of 25 , Mar 16, 2005
View Source
I wonder how much of an affect the sound card has on the figures. I use a
SoundBlaster Live! and can tell you that its output is not linear and its
third order IMD when using a two tone test signal is in the -30dB range. I
also have a USB SoundBlaster that does a worse job decoding digital modes,
than the internal SoundBlaster Live!.

Does anyone know of a low noise, low IMD, excellent decoding sound card?

73,

Mark N5RFX

At 06:37 AM 3/16/2005, you wrote:

>Paul
>Looking again at your figures below, at the oscillogram, and at the
>tone shaping, I would say that you are probably right...
>Can't explain yet why the audio sample I used is giving me such
>figures (see in file section) but something is not correct
>somewhere... 4.22dB "mean to peak" looks too much...
>Looking at it in the frequency domain, I can see that the frequency
>response of my audio-sample between 500 and 1500 is not flat but that
>the lower frequencies are attenuated by some 8dB, so it is probably
>why I am finding this wrong value...
• You are saying basically what I said back on the 13th. I STILL say that the best way to ensure a clean signal is to scope the output of the transmitter. Since
Message 1 of 25 , Mar 16, 2005
View Source
You are saying basically what I said back on the 13th.

I STILL say that the best way to ensure a clean signal is to scope the
output of the transmitter. Since all transmitters have a limited output,
simply use a scope to observe the peak voltage that the transmitter can
produce with CW. Then when using the digi modes set the output at just
below this for the peak signal. Your transmitter is now set where it
should be clean. Use the audio control, not the RF power output control.
This could be the mic gain, or the output of the soundcard. Make sure
any processing is also off.

Steve/WM5Z

Patrick wrote:

>
> Tomi
> I do not agree with your interpretation of the Crest-factor.
> You will find anywhere that the crest-factor of a pure sinewave is
> 1.414...
> -this is the peak voltage value, divided by the RMS voltage value
>
> If you keep thinking in terms of voltage values converting to dB
> gives 20log1.414 = 3dB
> A pure sinewave has a 1.414 or 3dB crest factor...
>
> In practice any modulation will have a crest-factor equal(pure-FSK)
> or superior to 3dB...
>
> Now forget about the crest factor and just consider what is
> interesting for us: mean to peak power values -both being "average
> power values"- (average power being the square of the RMS voltage
> divided by the load (*))
> - In this case the peak (avg) power is the wattmeter reading when
> you "tune" or when you send a RTTY mark
> - the mean (avg) power would be a thermical-wattmeter (bolometer)
> reading... (a normal wattmeter may indicate anything between mean and
> peak depending among other things on the instrument technology...)
>
> I don't have a bolometer, but my conclusion from waveform analysis
> (and from temperature elevation of my IC706 !)is that the "mean to
> peak" for Olivia is in the 4dB area, which is something similar to
> CW... So about 40W with a 100W rated transceiver.
>
> (*)As mentionned in ARRL handbook RMS-power is a mathematical
> curiosity whcih has no physical significance. In practice you'll see
> everywhere references to RMS-power, but it should be called "average
> power" (the product of RMS-voltage by RMS-current). The english
> terminology is extremely confusing...
>
>
>
>
>
>
>
> --- In oliviadata@yahoogroups.com, Paul L Schmidt <k9ps@a...> wrote:
> > Tomi Manninen wrote:
> > > On Tue, 2005-03-15 at 16:18, Mark Miller wrote:
> > >
> > >
> > >>Question for the group: Why does Olivia have a 7.22 dB crest
> factor?
> > >
> > >
> > > The symbols in Olivia are shaped. See
> > >
> > > http://homepage.sunrise.ch/mysunrise/jalocha/mfsk_spec.html
> > >
> >
> > True, but not *that* much shaping...
> >
> > Here are my numbers:
> >
> > mfsk_tx random.dat random.mfsk
> >
> > sox -t raw -sw -r8000 random.mfsk -t wav /dev/null stat
> >
> > Maximum amplitude: 0.538757
> > Minimum amplitude: -0.538757
> > Midline amplitude: 0.000000
> > Mean amplitude: 0.000000
> > RMS amplitude: 0.329407
> >
> > .538757 / .329407 = 1.63522
> >
> > 20 log (1.63522) = 4.27 dB ... which needs
> > to be dropped by 3 dB since we're comparing an RMS
> > voltage to an instantaneous peak (rather than the RMS
> > value of the signal at the peak).
> >
> > That puts it down to about a 1.63 dB crest factor...
> >
> > e.g. if you're running 50 watts RMS output, your
> > PEP will be 67 watts... which seems reasonable for
> > what I've experienced.
>
>
>
>
>
> The ARRL now lists Olivia as a "valid" digital mode for
> http://www.arrl.org/FandES/field/regulations/techchar/
>
>
>
>
>
> <http://us.ard.yahoo.com/SIG=1297543l5/M=298184.6018725.7038619.3001176/D=groups/S=1705063108:HM/EXP=1111050841/A=2593423/R=0/SIG=11el9gslf/*http://www.netflix.com/Default?mqso=60190075>
>
>
>
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• Mark You may browse the RTTY archive on contesting.com... I remember that the subject has been discussed several times. With my previous PC I was using a
Message 1 of 25 , Mar 16, 2005
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Mark
You may browse the RTTY archive on contesting.com... I remember that
the subject has been discussed several times.
With my previous PC I was using a "guillemot home studio pro 64"
which had "low noise inputs and outputs"... It was excellent, but it
was an ISA card !
Now I just use the default card which is on the motherboard.
To be honnest I never did IMD measurements before, but as it was an
excellent idea, I immediately did it...

- generated a closed-spaced 2 tones file using cool edit DTMF
generator (1100 and 1200 Hz)
- played it with the windows player
- recorded it using pathsim as digital recorder

I have uploaded the result in the file section... no IMD product
higher than -85dB...
NB I did not use the line input, but I looped the signal internaly
using "out mix" as recorder input. It may be a bit worst looping
externaly with an audio cable, but honnestly don't think that 30dB is
something normal... for a transceiver yes, but definitely not for an
audio device...

Patrick

--- In oliviadata@yahoogroups.com, Mark Miller <kramrellim@c...>
wrote:
> I wonder how much of an affect the sound card has on the figures.
I use a
> SoundBlaster Live! and can tell you that its output is not linear
and its
> third order IMD when using a two tone test signal is in the -30dB
range. I
> also have a USB SoundBlaster that does a worse job decoding digital
modes,
> than the internal SoundBlaster Live!.
>
> Does anyone know of a low noise, low IMD, excellent decoding sound
card?
>
> 73,
>
> Mark N5RFX
>
> At 06:37 AM 3/16/2005, you wrote:
>
>
> >Paul
> >Looking again at your figures below, at the oscillogram, and at the
> >tone shaping, I would say that you are probably right...
> >Can't explain yet why the audio sample I used is giving me such
> >figures (see in file section) but something is not correct
> >somewhere... 4.22dB "mean to peak" looks too much...
> >Looking at it in the frequency domain, I can see that the frequency
> >response of my audio-sample between 500 and 1500 is not flat but
that
> >the lower frequencies are attenuated by some 8dB, so it is probably
> >why I am finding this wrong value...
• Hmmmm. Interesting finding. I am using a Creative Labs CT4750 (\$29.00 US) which produces aproximately 1.25 volts peak output. It is designed to drive amplified
Message 1 of 25 , Mar 16, 2005
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Hmmmm. Interesting finding. I am using a Creative Labs CT4750 (\$29.00
US) which produces aproximately 1.25 volts peak output. It is designed
to drive amplified speakers, no power amp on board. These boards are
equal to the SB-64, but no speaker driver.

The board was set up to sample at 11025. The single tone distortion is
less than .005% per my HP334A distortion analyzer. Using 2 tones, and an
CT Systems audio spectrum analyzer (NOT FFT), set up with 10 Hz
bandwidth and 100 second sweep my only artifacts are anti-aliasing
errors that are just at -54dB. The dynamic range of this spec-an is
limited to 60 dB. Can not see any IMD within the audio passband of 10 to
8000 hz. The ailising errors are all above 18Khz.

BTW, I did these tests to proof these boards for a project for the US
Army. My samples are all date coded 8/27/04 and the quantity tested is
5. I also tested 3 onboard soundcards using the ASUS P4VP-MX
motherboards. These are Realtek ALC655 sound decoders. My findings there
were very comprable, though the output level max was slightly lower (1.1
Vpeak) The single tone distortion is .007% and the IMD just shows up at
-63 dB. There was no visible anti-aliasing errors.

In all tests, the termination of 600 Ohms was in place, and no
transformer is used between the HP334A and the computer. The case of the
PC was connected to my system ground, and the HP334A was floated which
minimized overall noise. The audio spectrum analyzer was connected to
the output of the HP334A, and also the TERM was engaged on the spec-an.

The test audio was derived from a testfile (SNDTSTxx.WAV) that I have
that comes from a NAB broadcast CD aquired a few years ago. It has
several files at various frequencies, 400Hz, 1000Hz, 2000Hz etc.
single tone. It also has a two-tone test file of 1030 Hz and 900. Note
that these files are WAV files and not just playing through the CD
output. I get the same whether I play the sound files from the CD or
from the hard drive.

I did no tests recording the audio, so can not comment on that. If I get
some time I will set up a PC with one of these and do some tests on the
recording input. Would be interesting.

Hope this helps you.

Steve/WM5Z

Mark Miller wrote:

> I wonder how much of an affect the sound card has on the figures. I
> use a
> SoundBlaster Live! and can tell you that its output is not linear and its
> third order IMD when using a two tone test signal is in the -30dB
> range. I
> also have a USB SoundBlaster that does a worse job decoding digital
> modes,
> than the internal SoundBlaster Live!.
>
> Does anyone know of a low noise, low IMD, excellent decoding sound card?
>
> 73,
>
> Mark N5RFX
>
> At 06:37 AM 3/16/2005, you wrote:
>
>
> >Paul
> >Looking again at your figures below, at the oscillogram, and at the
> >tone shaping, I would say that you are probably right...
> >Can't explain yet why the audio sample I used is giving me such
> >figures (see in file section) but something is not correct
> >somewhere... 4.22dB "mean to peak" looks too much...
> >Looking at it in the frequency domain, I can see that the frequency
> >response of my audio-sample between 500 and 1500 is not flat but that
> >the lower frequencies are attenuated by some 8dB, so it is probably
> >why I am finding this wrong value...
>
>
>
>
> The ARRL now lists Olivia as a "valid" digital mode for
> http://www.arrl.org/FandES/field/regulations/techchar/
>
>
>
>
>
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