understanding the frequency accuracy

Hi all,

I have a question concerning the frequency reference accuracy of SA44B.
In general this is 1ppm that equals 1×10 -6th power.
so if I want to measure around 440 Mhz I have the result only as exact as +- 440 Hz right?
If I need that to be more exact I will have to attache an external frequency reference.
I have a GPS one that performs with a minimum of 1×10 -9th Power which equals 1ppb.
Would that mean the SA44B is as accurate as +- 1.44Hz?
(1 Hz + 0.44 Hz as stated in the specs)

thank you for your help

Sebastian

The actual frequency error for sweeping is (reference error + 1 sample), so if you have a sweep with a “bin size” of 10 Hz (around 40 Hz RBW), and a 1 ppb timebase, your marker should read within 10.44 Hz of the actual frequency.
You can calculate bin size as (span / number of points).
If you are using the frequency difference meter or the modulation analysis tool center frequency on a CW, the frequency error should be very small, as long as your signal to noise level is good. With the frequency difference meter, I typically see something like 0.01 ppb error.

Hi Justin,

thank you for your quick response.
So if I want to align a the TX of a DMR TRX @ 440 Mhz f.e. or maybe show that it is not meeting the specs I would use the SA44B in frequency difference meter mode or I think better Modulation analysis with my 1ppb Timebase and that would lead me to an accuracy of about +- 0.01ppb = 0.0044 Hz of the TX´s center frequency and the corresponding 4FSK points?

sorry for being a pain but Im just getting into Spectrum analysis –
I understand the ingredients but still cant bake the cake

thank you

Sebastian

The frequency difference meter would be good for CW signals. I don’t know how it’ll perform with 4FSK. You might try our modulation analyzer in zero span for that. I think I’ve seen around 1 Hz typical error on readings there with time bases locked.
For a CW, using the frequency difference meter, a typical accuracy would be 0.01 ppb plus time base error, so in your case, +/- 1.01 ppb. At 440 MHz, +/- 0.4444 Hz.
Adding modulation complicates things a lot.

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