Re: Spectrum Frequency Axis display issue in R1732 - with low sample rate

Ian DXer
 

On Mon, Mar 16, 2020 at 03:16 AM, prog wrote:
When not using the maximum sample rate, the receiver switches to Low-IF mode. This means the actual LO you are calibrating is not at the center of the spectrum, but rather at the upper edge. That's definitely not going to help with the calibration.
The solution is to use the max sample rate, tune near the center and set a very high FFT resolution. 
Thanks Prog. Very much appreciate this information.
I won't be able to achieve better results on MW X-band at present, but if I wish to attempt better freq accuracy in VHF band/channel(s) in future I'll remember your notes.
In fact I've now entered them in my own calibration doc

Prog> Also, it is recommended to calibrate at a higher frequency in the high VHF
Yes noted earlier.

Prog> or the L-Band (yes, the receivers also ~work between 1200 and 1700 MHz).
Thanks for the reminder re availability of this band. Must have a listen/play up there later :-)

jdow> what is the step size of the frequency synthesizer in the HF+ models AND the other "calibrated" SDRs? If you want extreme accuracy get to know your instruments intimately so you know their sources of error.

Absolutely! Couldn't agree more :-)  All those factors were thought of.
Back in my college years at the school of Electronics Engineering one of the expectations of our teachers were for students to account for all possible sources of error & their contribution/influence on the results in our concluding
remarks in our lab reports. Mind you having a 100kW TV transmitter tower right next door to the classrooms & student lab equipment (especially when 'some' test equipment leads were unshielded) really didn't help with some of 
results. I look back & smile ;-)





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