Freq calibration

[owenduffy]

I have downloaded and installed the latest firmware to date.

I am trying to calibrate the frequency, and the menu options are different to the various descriptions I find online.

Can you point me to a reliable reference for calibrating freq on this current firmware.

Owen

[Erik]

Go to CONFIG/EXPERT CONFIG/FREQ COR
Enter the frequency correction in part per billion

[owenduffy]

Hi,

I had tried that.

So in detail, I set the device to sign gen mode at 10MHz output and measured 9.999986MHz which is 1400ppb low.

I tried entering -2000ppb and it changes the freq to 9.999992MHz, somewhat short of the calculated value (whereas I expected it to increase to 10.000006MHz).

Successively changeing this value to -1000,-2000, -3000, -4000 results in rather large steps in output freq. The next step was to 10.000032MHz.

I do not seem to be able to set it between 9.999992MHz and 10.000032MHz.

I do not seem to be able to adjust freq calibration in sufficiently small steps to get it close to say 1e-7.

Is there an issue with the firmware?

Owen

[Erik]

No
The PLL can only tune in either 28 or 56 Hz steps so 8 Hz low is excellent.

[owenduffy]

You say 28Hz steps... is that at 10MHz, is it more generally 2800ppb?

Should I be doing the cal at a higher freq, eg 100MHz?

Owen

[Erik]

Same step at any frequency so best to calibrate
frequency at highest frequency

[owenduffy]

Thanks... that worked better. I achieved error of 60ppb using 200MHz output. I expect its stability is worse than that.

Owen

BTW, do you think people often use the µ and m multiplier buttons? Perhaps k would be useful?

[Erik]

Ah, yes, for PPB k is better