[vna] measurement of quartz crystal

[Koji Terai]

Hi Tom,

Thanks for the input. I understand that you have a lot of work to do for
the new version of the software.
You have been working on creating a model of the directional coupler ripple,
does this means that your effort will improve accuracy of S11 measurement?

  Best 73,
      Koji/ JA3XNO

----- Original Message ----- 
From: "Tom McDermott" <tom.mcdermott4 at verizon.net>
To: "'TAPR/Ten-Tec VNA Users List'" <vna at lists.tapr.org>
Sent: Tuesday, December 27, 2005 11:44 PM
Subject: RE: [vna] measurement of quartz crystal


Hi Koji,

Thanks for the report. I saw the bug one time, but have not looked
carefully for it yet. I did find a couple of errors in how the frequency
grid is computed, and that is being revised in the new release. I think it
may address the problem, but will test it first. The major effort in the new
release is modeling the directional coupler ripple, and it's been difficult.
I hope to have something available this week. Will probably release a beta
since there are many changes in the new code.


-- Tom, N5EG






> -----Original Message-----
> From: vna-bounces at lists.tapr.org
> [mailto:vna-bounces at lists.tapr.org] On Behalf Of Koji Terai
> Sent: Monday, December 26, 2005 10:04 AM
> To: TAPR/Ten-Tec VNA Users List
> Subject: Fw: [vna] measurement of quartz crystal
>
>
> Hi Tom,
>
> Have you acknowledged the bug that I reported on my former
> e-mail below? I wonder when new version of the software comes up?
>
> Best 73,
>
>   Koji
>
>
>
>
> ----- Original Message ----- 
> From: "Koji Terai" <kj_terai at ybb.ne.jp>
> To: "TAPR/Ten-Tec VNA Users List" <vna at lists.tapr.org>
> Sent: Tuesday, December 06, 2005 5:04 PM
> Subject: Re: [vna] measurement of quartz crystal
>
>
> > Hi, Tom!
> >
> > Thank you for your agile res.
> >
> > Yes, I knew the phase detector is not capable to determine
> measuring
> > parameters at a lot of attenuation as the manual already addresses,
> > and I just tried it with a crystal with little hope. I
> think that to
> > measure a crystal is one of most difficult
> > trials and I might be too demanding.
> >
> > I understand that frequency sweep will take a longer time when
> > measuring a
> > network
> > which has long-delay such as very narrow width B.P.F.s.
> >
> > While measuring crystals, I found a strange thing that I tried to
> > place a
> > marker on a curve displayed
> > but the marker did not appear on the right place where I
> clicked on, and I
> > am
> > wondering if this strange thing relate to the software bugs
> you found.
> >
> > The VNA has just been released, and I hope that the VNA will be
> > brushed up
> > by you developer
> > and other users in terms of software and hardware from now on.
> >
> > I will be happy if I have a notification when a new version of the
> > software is released.
> >
> >
> > 73 w/ best regards,
> >
> >  Koji/ JA3XNO
> >
> > ----- Original Message -----
> > From: "Tom McDermott" <tom.mcdermott4 at verizon.net>
> > To: "'TAPR/Ten-Tec VNA Users List'" <vna at lists.tapr.org>
> > Sent: Tuesday, December 06, 2005 11:36 AM
> > Subject: RE: [vna] measurement of quartz crystal
> >
> >
> > Hi Koji:
> >
> > The phase detector of the VNA is not capable of measuring correctly
> > when
> > the
> > input signal is attenuated a large amount (both S21 and S11
> measurements).
> >
> > I have also found some bugs in the software that affect crystal
> > filters:
> >
> > * Severe S21 measurement error when the time delay of the
> network is
> > high (the VNA sweeps too fast for long-delay networks).
> >
> > * Error in the frequency generation routine that causes the VNA
> > software
> > to
> > have a stop_frequency error for very narrow sweeps (few kilohertz),
> > grid=1020, and it also forgets to set the frequency error from the
> > detector
> > calibration.
> >
> > I have fixed these errors, they will be incorporated in the next
> > software release on the TAPR website.
> >
> >
> > -- Tom, N5EG
> >
> >
> >
> >
> >
> >> -----Original Message-----
> >> From: vna-bounces at lists.tapr.org
> [mailto:vna-bounces at lists.tapr.org]
> >> On Behalf Of Koji Terai
> >> Sent: Monday, December 05, 2005 2:07 AM
> >> To: TAPR/Ten-Tec VNA Users List
> >> Subject: Re: [vna] measurement of quartz crystal
> >>
> >>
> >> Hi Tom,
> >>
> >> Thank you for your res and suggestions.
> >>
> >> So far, I had no chance to use VNAs, but I read some books before
> >> that described importance
> >> of defining measurement planes and consistency of a
> >> testfixture to be used. Any way I have just started to use
> >> the VNA and I have to learn more about
> >> measurement
> >> by the VNA.
> >>
> >> The way I tried was that I measured crystals in S12 mode
> and tried to
> >> read out f(o) and f(a)
> >> from curves of magnitude and phase, but as for f(o), I had
> to expand
> >> frequency pitch
> >> to read the frequency very precisely then the peak was
> >> displayed very flat,
> >> almost it turned a line
> >> and I could not find where the peak was. So I gave up reading
> >> our f(o) from
> >> a magnitude and I
> >> read f(o) from a curve of phase instead, but as for f(a), a
> >> curve of phase
> >> changed in every sweep
> >> so that I could not determine f(a). I think that a crystal
> >> exhibits great
> >> attenuation at f(a) and the VNA
> >> is not able to determine phase change at around f(a) due to
> >> the limitation
> >> of the phase detector of
> >> the VNA. I am not sure the way I tried was correct or not, or
> >> there are some
> >> better way to measure
> >> a crystal at this moment.
> >>
> >> Koji/ JA3XNO
> >>
> >>
> >> ----- Original Message -----
> >> From: "Tom McDermott" <tom.mcdermott4 at verizon.net>
> >> To: "'TAPR/Ten-Tec VNA Users List'" <vna at lists.tapr.org>
> >> Sent: Sunday, December 04, 2005 8:08 AM
> >> Subject: RE: [vna] measurement of quartz crystal
> >>
> >>
> >> Hi Koji:
> >>
> >> The TAPR VNA can be calibrated against an external reference
> >> oscillator for good frequency accuracy. However in order
> to determine
> >> accurately the 4 motional parameters (Ls, Rs, Cs,
> >> Cp) of the crystal requires extreme precision of the fixture stray
> >> reactances. I am not an expert in crystal filters, but I think the
> >> 4-parameter model is used pretty extensively in filter
> modeling. 100
> >> Hz frequency accuracy is not a problem, but stray reactances are a
> >> problem.
> >>
> >> I think Agilent has a software package to extract the motional
> >> parameters from swept S parameters. The TAPR unit does not
> have this
> >> software, but it perhaps could be an interesting exercise;
> certainly
> >> for those who enjoy working on software.
> >>
> >> Key to measurement is that the fixture parallel
> measurement will be
> >> contaminated by fixture parallel capacitance. This will rotate the
> >> series resonance frequency away from R + j Zero X and must be
> >> compensated. The parallel anti-resonance will have the same issue.
> >> S-parameters will show the crystal resistance as compared
> to 50 ohms
> >> but the fixture will rotate the phase angle. The fixture
> perhaps can
> >> be calibrated out of the measurement if the crystal is
> replaced with
> >> a 50 ohm resistor, but I have never tried it.
> >>
> >> -- Tom, N5EG
> >>
> >>
> >>
> >>
> >>
> >>
> >> > -----Original Message-----
> >> > From: vna-bounces at lists.tapr.org
> >> [mailto:vna-bounces at lists.tapr.org]
> >> > On Behalf Of Koji Terai
> >> > Sent: Saturday, December 03, 2005 9:14 AM
> >> > To: vna at lists.tapr.org
> >> > Subject: [vna] measurement of quartz crystal
> >> >
> >> >
> >> > Hi, everyone! I would like to know if the VNA is able to
> determine
> >> > resonant frq. and antiresonant frq. of a quartz crystal in
> >> accuracy of
> >> > 100 Hz. I plan to construct Cohn type crystal filters, and
> >> I tried to
> >> > measure crystals but I was not able to measure these two
> >> frequencies
> >> > definitely, especially ant frequency measurement was very
> >> critical. I
> >> > am looking forward to a good solution for this.
> >> >
> >> >  Koji
> >> >
> >> >
> >> >
> >> > _______________________________________________
> >> > vna mailing list
> >> > vna at lists.tapr.org
> >> https://lists.tapr.org/cgi-bin/mailman/listinfo/vna
> >> >
> >>
> >>
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> >>
> >>
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> >
> >
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