K3 question--TCXO or another filter?

[Steve Ward]

Greetings all,

I'm getting pretty close to the time I'm expecting to see a Katiegram,
and I'm thinking about adding either the TCXO or the 6KHz filter to my
order.

I do a lot of PSK-31 and I'm wondering if most folks find the stock
oscillator sufficiently stable for digital or if the TCXO is better to have?

Thanks for your advice,

Steve
AD7OG

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[michael taylor-3]

On Mon, Aug 4, 2008 at 10:53 AM, Steve Ward <[hidden email]> wrote:
>
> I'm getting pretty close to the time I'm expecting to see a Katiegram, and
> I'm thinking about adding either the TCXO or the 6KHz filter to my order.
>
> I do a lot of PSK-31 and I'm wondering if most folks find the stock
> oscillator sufficiently stable for digital or if the TCXO is better to have?

Given that the regular oscillator in the K3 is better than many if not
most amateur radio HF transceivers, I do not believe you will see a
noticeable improvement with the higher quality TXCO. As far as I know
the typical HF user will not notice any improvement by having the TCXO
in standard (sane?) operating conditions at HF to 6 meter frequencies.
So in short, the stock K3 is more than adequate for PSK-31 operating.

The stock XO is  +/- 5 ppm (0-50 C) TCXO standard (@49.380 MHz). The
upgrade is to +/- 1ppm. The average user won't notice the +/- 4Hz
improvement. I believe many users would have issues accurately
calibrating their K3 to +/- 1ppm. As far as I know _reception_ of
WWV/CHU's HF (or WWVB LF) signals are not that accurate. A GPSDO (GPS
disciplined ovenized oscillator) would be typically used to in that
situation.

My understanding is that beside amateur metrologists (e.g. time-nuts),
and the typical users of the upgraded TCXO are microwave perhaps
mobile/rover VHF operators who use transverters to multiply the K3 HF
output to the higher operating frequency, where you want minimal error
(i.e. drift, jitter) in the K3's oscillator, because this error will
be magnified (multiplied) by transverter as well.

-Michael, VE3TIX
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[Dave, G4AON]

The difference between TCXOs is 4ppm not 4 Hz. The standard TCXO can be
+/- 250 Hz at 50 MHz, the optional one can be +/- 50 Hz at 50 MHz or
perhaps +/- 25 Hz once the firmware is changed to allow the supplied
calibration table to be used. Using the optional 1ppm TCXO in my K3
results in a typical accuracy of within 20 Hz at 50 MHz, under normal
shack temperatures. I run a home brew GPS derived standard for
calibration purposes.

The K3 is one of the few transceivers that can be adjusted for frequency
without taking a cover off or needing a trim tool, it can be easily
calibrated every hour, every day or whatever - if that's what floats
your boat. Whether you need the higher accuracy is only something you
and your wallet can decide.

73 Dave, G4AON
K3/100 #80
-----------------
"The average user won't notice the +/- 4Hz
improvement"
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[michael taylor-3]

On Tue, Aug 5, 2008 at 1:44 AM, Dave G4AON <[hidden email]> wrote:
> The difference between TCXOs is 4ppm not 4 Hz. The standard TCXO can be +/-
> 250 Hz at 50 MHz, the optional one can be +/- 50 Hz at 50 MHz or perhaps +/-
> 25 Hz once the firmware is changed to allow the supplied calibration table
> to be used. Using the optional 1ppm TCXO in my K3 results in a typical

Thank you Dave (and others who corrected me in private), you are
correct I did make a mistake, the 5ppm / 1ppm ( 5E-6 / 1E-6) is
relative to the oscillator's frequency, 49.380 MHz, so the actual
expected frequency error (tolerance / stability) is as Dave gave
above.

-Michael, VE3TIX
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