Invest limit bw ssb to 3 k

[Brumi-2021]

Second official attemp PR to try to close that issue #2180 (but all this week , we had several testing trial fw's between)
Special thanks to ly2ss , for his patience and deep checking support ,and for finding several bugs. Hopefully this time , all should be OK ,

We are correcting previous aliasing folding effect , when sending an audio sweep signal.
And we are also addressing a proper BW SSB limitation. And moreover, we added the feature to be able to set up that BW , (but that user change settings , should be applied at PTT_OFF time . It is not a hot on the fly change . It will need PTT OFF ,setting change and PTT ON .

Here you can see all the three consecutive freq. limit changes 2k,3k,4khz in USB / LSB test transmission , saturating the mic with audio air blow noise , at very low local dBm level .

Let's wait for final test of ly2ss , and thanks in advance.

Pls. ly2ss, you can add the related comments here , after evaluating the latest fw , that I uploaded to the test-drive,

Cheers,

[ly2ss]

The TX band with is limited to 2kHz and 3kHz in LSB/USB modes correctly.
While sweeping, no "folding" effect is noticed.

[Brumi-2021]

Thanks @ly2ss !
I will have a look later in the 4k option .
And if it is a silly error I will correct it . But if it is an issue that needs long invest with proper cable , I will remove that option by now
Later I will check it and lets decide .
Cheers

[Brumi-2021]

Ok , I checked 4khz implementation and apparently seems well coded.
I could not see an obvious error.
Then as we agreed with @ly2ss , we can proceed with that merge ,(just removing that 4khz -pending to be investigated later)
I already removed 4k option from the menu. (once I handmade the special cable , I will investigate about those folding alias effect on 4khz , now without proper settings , very hard to debug)
.
So please, let's proceed with its merge, ALREADY VALIDATED by @ly2ss ,

Thanks to all,

Cheers.

[gullradriel]

Good to go