I'm measuring the 300 MHz Cal output like it states, and it's about 80 Hz off.
I do the following -
3. Press the following analyzer keys.
PRESET
FREQUENCY, -2001, Hz
CAL, More 1 of 4, More 2 of 4, More 3 of 4
SERVICE CAL, CAL TIMEBASE
4. A number will be displayed in the active function block of the
analyzer display. This is the setting of the DAC (0 to 255) which
controls the frequency of the internal time base. Use the knob or
keyboard to change the DAC setting until the frequency counter
reads 300 MHz ±75 Hz (±0.25 ppm).
But no change I make to the DAC values makes any change in the Cal frequency whatsoever.
What am I doing wrong?
Does it have option 004, maybe?
Does it have option 004, maybe?
Thanks for responding.
No, it does not. I did read about that option adjustment in the procedures. It doesn't list that option on the back with the other options it has. Seems strange that it would give the DAC control and not have it do anything if it was meant to have it adjusted internally.
Do you think I should inspect the unit inside for that adjustment?
Check in the software. There's a way to display the options, maybe it was added later and not added to the list on the back. Or you can open it and look inside.
Check in the software. There's a way to display the options, maybe it was added later and not added to the list on the back. Or you can open it and look inside.
Yea I'll get in there and see what I can find. I'm going to a local Hamfest this morning but will report back later ...
Well you were right - it does have the 10 MHz Precision Frequency Reference. Here are some before and after pics of the adjustment. Frequency counter is referenced to my GPSDO. Everything is spot-on now.
I have the same SA and I also have a GPSDO that I just finalized recently. I remembered that some time ago I adjusted the reference oscillator in the SA using just a Ublox GPS module set to output a 10MHz frequency and watching the drift on an oscilloscope. I was curious what's the result of that adjustment now that I have a reliable GPSDO.
Here's the result after about 4 - 5 hour warm-up. It was within 3 - 4 counts after about 2 hours.
I have the same SA and I also have a GPSDO that I just finalized recently. I remembered that some time ago I adjusted the reference oscillator in the SA using just a Ublox GPS module set to output a 10MHz frequency and watching the drift on an oscilloscope. I was curious what's the result of that adjustment now that I have a reliable GPSDO.
Here's the result after about 4 - 5 hour warm-up. It was within 3 - 4 counts after about 2 hours.
That's great. The manual says to let the ref. osc. warm up for 24 hours before adjustment, but after an hour it wasn't moving so I went ahead and adjusted mine. After less than 10 m warmup now it is good to go @ 300.000000 MHz.
