SEEK behaviour related to band limits #165
Description
Discussed in #164
Originally posted by G8PTN June 23, 2025
Hi,
This is not necessarily a firmware bug, but a possible feature of how the SI4732-A10 works.
A user in another forum noticed an interesting issue with the hardware seek behaviour on the SI4732-A10.
The seek frequencies appear to be based on the seek spacing and the lower band limit.
goshante/ats20_ats_ex#44 (comment)
I replicated the issue on the ATS-MINI firmware which actually has a fixed AM seek spacing of 5kHz.
Example 1:
Lower band limit = 531 kHz
Manual tune to a frequency on a 5kHz boundary, e.g. 600 kHz.
With a debug print statement added in void showFrequencySeek, start “Seek Up”.
Although not all frequencies get printed, they all follow 531kHz + (5kHz x n), where n is an integer value.
606
611
621
626
636
641
651
656
666
676
681
Repeating the same test where the lower band limit is on a 5kHz boundary.
Example 2:
Lower band limit = 150 kHz
Manual tune to a frequency on a 5kHz boundary, e.g. 200 kHz and start "Seek Up"
Again, although not all frequencies get printed, they all follow 150kHz + (5kHz x n), where n is an integer value.
210
215
225
230
240
245
255
265
270
280
The workaround implemented by the user was to set the lower band limit to a common multiple of the seek spacings available.
Example:
Assuming available seek spacings of 1kHz, 5kHz, 9kHz. 10kHz, a lower band limit of 450 kHz would be valid for all spacings.
I have not seen any direct reference to this in the application notes, although it is possibly implied by the recommended ranges and spacings,
Notes
The SI4732-A10 seek behaviour seems to depend on the configured lower band limit as well as the seek spacing. It may be the case that the upper band limit also influences the behaviour.
If the lower band limit is not on a valid boundary for the spacing, then the tuned seek frequencies, will not be as expected.
All tests with effectively the same patch applied in the latest ats-mini firmware related to the SI4755 library SI4735::seekStationProgress
I noticed that there are additional patches in the Chinese firmware (SI4735 library) relating to adjusting the frequency based on the step. I think this is covered in the ats-mini firmware (stepAdjust) and do believe it solves the hardware seek issue identified above.
The behaviour in FM mode may be the same? Not tested.
73, Dave