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

Ian DXer

Hi Youssef & all,

Recently I purchased a Leo Bodnar Mini GPS clock. One of the reasons for the purchase was for accurate (or improved) frequency calibration on my Airspy HF+ DP & measurements of Aussie x-band stations (more on that later). A number of issues have surfaced. I'll just deal with one in this message for the moment.

Problem: Seemingly (?) incorrect x-axis (spectrum frequency) display when sampled frequency carrier wave zoomed-in with low sample rate, pertains to display of frequency in SDR# left of the LeoBodnar GPS clock frequency generated carrier. (eg 248MHz in this case)

In regard to SDR# eg R1732 using the setup below

1. Windows 10 64bit
2. SDR# R1732
3. Sample rate 16kbps
4. Frequency: 248,000,000Hz (label H & G)
5. SDR# Display Resolution 32768 / Blackman Harris 4
6. LeoBodnar Mini GPS Clock set to output: 248,000,000Hz GPS & PLL locked
7. CW demodulation
8. Although Free Tuning mode shown in image. Carrier is centred on screen & issue occurs with Centre Tuning.

Refer to attached diagram to "see" the issue.

Basically, referring to diagram & the labels I've drawn. It seams to me that frequency labels on the spectrum display; labels B to F should be displaying 247.9999 rather than 248.000
, Label A is correct. This display anomaly only occurs when using the zoom display slider control at a significant zoom level, a low sample rate makes this all the more obvious.

Comparing this with SDR Console 3.0.20, SDR Console whilst it does have a x-axis display with an extra significant digit bit eg 247.999.98 vs 247.9999(SDR#), SDR Console is displaying carrier position correctly along the frequency x-axis correctly at high zoom levels.

Can you comment &/or investigate this Youssef?  

Thanks very much.


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