XG3 Calibration from 10MHz Standard?

[MaverickNH]

I'm not quite sure how to calibrate my XG3 against the 10MHz output of a GPSDO. Appreciate help on correct tab, button, etc, on the XG3 Utility and how best to connect the GPSDO to XG3, or through my K3S which is connected to the GPSDO.

Thanks, Bret/N4SRN

[ng7m]

Hi, normally, you would drive a frequency counter with your 10mhz GPSDO output... i.e. you need to have a frequency counter that accepts a 10mhz input as a reference.  Then you would measure the output of the XG3 for any given frequency and adjust the parameters in the software that programs the crystal offset in the XG3 firmware.  You can find some good deals on an HP 5384A on flea-bay for example... if you look around.

Just make sure you don't over drive your frequency counter based on the peak to peak voltage output from the XG3.  The same holds true for the output from your GPSDO into your frequency counter... make sure the PVP output meets the frequency counter specification.

Max NG7M

[Don Wilhelm]

If you do not have a frequency counter, there is another way.
Use XG3 Utility to set the XG3 to provide a 10 MHz output.
Listen to the 10 MHz reference in your receiver in CW mode and peak the
signal at your sidetone pitch.  Then listen to the XG3 without touching
the receiver.  Adjust the XG3 software parameters to produce a signal at
*exactly* the same sidetone pitch.

73,
Don W3FPR

On 9/18/2016 5:25 PM, ng7m wrote:

> Hi, normally, you would drive a frequency counter with your 10mhz GPSDO
> output... i.e. you need to have a frequency counter that accepts a 10mhz
> input as a reference.  Then you would measure the output of the XG3 for any
> given frequency and adjust the parameters in the software that programs the
> crystal offset in the XG3 firmware.  You can find some good deals on an HP
> 5384A on flea-bay for example... if you look around.
>
> Just make sure you don't over drive your frequency counter based on the peak
> to peak voltage output from the XG3.  The same holds true for the output
> from your GPSDO into your frequency counter... make sure the PVP output
> meets the frequency counter specification.
>
> Max NG7M
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/XG3-Calibration-from-10MHz-Standard-tp7622599p7622634.html
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[ng7m]

Bret, Don brings up a great point if you don't have a frequency counter.

Per Don's suggestion you could even get very close if you zero beat your K3 to a WWV carrier on 10, 15 or 20 mhz.  This is really easy to do with the K3 reference offset setting in the Config menu...

Tune into the WWV 10mhz carrier for example on CW and switch back and forth from CW to CW-R... i.e. from side band to side band with the Alt option on the K3 panel... as you do this, make sure you are in the REFCAL K3 menu and tune the offset until you can't hear a difference between the side band tones via switching from CW to CW-R(eversed).  If you have a good ear, you can be very accurate.  Oh, make sure you K3 is nice and warmed up before you do this.

Once you have the K3 REFCAL set as close as you can tell to a WWV carrier, you will be even closer if you follow Don's suggestion about listening to the 10mhz output of the XG3 on your K3 receiver.  Pretty easy to get very, very close.

Now if you really want to get anal!  As in time-nuts anal, you could pick up a used HP Agilent 8657 (or similar) frequency generator.  Drive it with your GPSDO and use the output in place of the XG3.  And then take it to another level of anal and get a nice used power meter to set the output of the frequency generator to as close as you can to the right power level to calibrate your S meter and power output on your K3. :)  It's a evil slippery slope of buying older lab grade equipment in an anal effort to have a very accurate signal reference and power output reference.  For a used power meter, I would look at the HP 438A series or even the newer version, but the thing that will set you back are the power sensors... they can pricey and still demand a premium on flea-bay.  Something like a HP 8484A to go along with your power sensor.  Make sure you know what you are getting for the HF range of power sensors etc.. and know what kind of power you are pumping into the power sensor.  If you don't attenuate the level input and adjust accordingly, you can fry the power sensor really quick and turn it into a several hundred dollar brick. ;)

Anyway, this kind of stuff is fun... you will find yourself buying all kinds of stuff just to have fun calibrating your gear.

Max NG7M

[Paul Saffren N6HZ]

Please realize that while the XG3 can be calibrated, it does not employ a temperature compensated or ovenized crystal oscillator as is found in higher end test equipment.  The unit can be  susceptible to temperature swings, holding it in your hand for several minutes, for example,  will affect the output frequency by a few Hertz.  

73,

Paul n6hz
XG3 PM

[MaverickNH]

I have a Rigol DG1022A Arbitrary Waveform Function Generator that has a counter that can measure 1 Hz to 200 MHz at 200 mVpp to 5 Vpp. My GPSDO is within this range for 10 MHz output (5 Vpp knocked down 3 dB). Seems the XG3 and XG3 should work fine, eh?

[briancom]

Hi Maverick,

The accuracy of the DG1022A stinks with the internal oscillator. Counter
likewise is inaccurate. Look at the specs -- something like 50 ppm.

I had one and measured how bad it really was.  In all other respects, it
was a decent product.  Apparently waveform synthesis is cheap and easy
but including a decent reference oscillator isn't at the Rigol's price
point.

When I tried to lock it to a Rb source and it was much better but still
off (low) a small amount.  To make it accurate, I had to use as
super-stable reference oscillator at slightly greater than 10 MHz
(10,000,000.175Hz) to get the RIGOL to be accurate.

73 de Brian/K3KO



On 9/19/2016 22:23 PM, MaverickNH wrote:

> I have a Rigol DG1022A Arbitrary Waveform Function Generator that has a
> counter that can measure 1 Hz to 200 MHz at 200 mVpp to 5 Vpp. My GPSDO is
> within this range for 10 MHz output (5 Vpp knocked down 3 dB). Seems the XG3
> and XG3 should work fine, eh?
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/XG3-Calibration-from-10MHz-Standard-tp7622599p7622667.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
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[Edward R Cole]

I've used the XG3 as signal source for testing/aligning VHF to mw
gear and do not worry about its accuracy/stability.  Instead I use my
EIP538 counter which is good to 26.5 GHz using either the internal
TCXO or my Rb source into the counter reference port.  At turn-on the
XG3 drifts quite a bit but after 20-min or so is slow enough for
aligning Rx front ends.  I have some heated xtal signal sources that
act the same way but operate at mw frequencies.

Its a fine piece of test equipment for its size/cost and generates
useful signals up to 1296-MHz.  Above 200-MHz the output level is
uncalibrated as you are using a harmonic of the output which will be
lower level.  So not real accurate for testing receiver MDS, still it
can make a ballpark test of a receiver (is it good, mediocre, or
bad).  For HF thru 2m quite good for measurements.

If you do not have a counter its harder to check its frequency.  Good
suggestions have already been made.  EIP538 is one of the best $500
investments I've made.  HP141T is another.

73, Ed - KL7UW
http://www.kl7uw.com
     "Kits made by KL7UW"
Dubus Mag business:
     [hidden email]

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