[Lowfer] TCXOs,

[Dale Rice]

12.8 MHz is exactly what I have been looking for to try and improve the
stability of my IC-735. A good oscillator should make it a bit better,
although the other oscillator ( the VCXO) will still cause some trouble. If
no one has a better use, I could use one, although I am a newbie on this
list. BTW what kind of cellphone uses that freq.? I have torn open a lot of
(US) phones and haven't found that one.

Dale Rice
KC7YKU
Williams, Oregon
Hifer:  DER on  13561.8


>
> Hi all,
>
> I recently acquired some temperature compensated oscillators that
> might be useful for improving the frequency stability of your beacon
> or receiver.  There are about seven left over; if one would help your
> rig, let me know and I'll mail it out.
>
> Obviously, if your present oscillator is GPS-locked, Rb, or oven
> controlled, this is not for you.  But if you are using a cheap
> clock module or a homebrew crystal circuit, and would like better
> stability, then read on.
>
> These units are KTXO-18 DIP modules by Kyocera, intended for use in
> cellular handsets.  Comments below are based on the manufacturer's
> spec, as well as my tests on one part from the lot.
>
> Nominal frequency is 12.8 MHz.  Output is AC coupled, but can drive
> HCMOS or LSTTL by just connecting two resistors to the output.
>
> There is a manual trimmer but no electrical frequency control.
> Kyocera spec is +/- 3 ppm minimum adjustment, but the actual range is
> about +/- 20 ppm, in the usual 180 degrees, so it takes a while to set
> it better than 0.1 ppm.  Before adjustment, the test unit measured
> 12.8000121 MHz at 20 deg. C.
>
> Frequency versus voltage is pretty good.  Spec is +/- 0.3 ppm over a
> +/- 5% change in supply.  Actual shift was only 1 Hz for 200 mV
> change.  I would guess that most systems would exhibit a supply
> voltage change of less than 10 mV during a half hour transmission;
> this would be less than 1 mHz at LF.
>
> Temperature stability, however, is not so great.  Claimed is +/- 3 ppm
> from -20 to +60 C.  But the curve has at least two inflections, and
> the slope is about 0.05 ppm per degree at say, 15 C.  If you consider
> decent lowfer stability to be 0.01 Hz over a half hour transmission,
> then the temperature would need to change no more than 2 C per hour.
> Most indoor living spaces conform, but many shacks are in locations
> that don't.
>
> Long term drift spec is 1 ppm per year.  The test unit has been
> connected to a counter for the past month.  During the first week,
> frequency fell about 0.1 ppm, and then started to rise.  It's
> presently increasing about 0.01 ppm per week.
>
> I found an interesting PIC-based timer that uses this oscillator at
> http://www.picfun.com/equipj39.html .  The above page has a spec,
> picture, and schematic showing how to drive a PIC.  If you have Win 2k
> or XP, there should be no trouble viewing the page, otherwise you may
> need Japanese fonts or language pack.
>
> I was unable to find the official spec for this part on the web.  It
> is obsolete, since current handsets use surface mount parts.  However,
> I believe that the KT18 series is electrically almost identical.  At
> http://global.kyocera.com/frame/product/electro/ec/english/tmn/index.html
> you can download a TCXO catalog in English.
>
> Let me know if you would like one of these parts.
>
> 73,
>
> Stewart KK7KA
>
>
>
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