Re: next ubitx

Ashhar Farhan
 

There are several ways to do this. ALC is just one way. An easier approach is to do it in software. This needs a software that can control the 'mic volume'. you could set the value differently for each band.

there is another pay-off with software mic gain, it can make a major difference to the tx IMD. At voice peaks, the tx linear chain compresses. The gain is not constant between low and high levels of modulation. This is what the in-channel IMD is. Now, if we have a look up table that amplifies the peaks more than the lows, we can 'correct' the gain back to being linear.  This simple concept goes by the name of 'pre-distortion' in the SDR world.

-f

On Thu, Apr 18, 2019 at 9:21 AM Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io> wrote:
If you want to electronically adjust TX power out on the uBitx, talk to John, VK2ETA

He's got that working with no hardware mods for SSB:
    https://groups.io/g/BITX20/message/45781
and now with some minor mods for CW:
    https://groups.io/g/BITX20/message/67981
    
Jerry, KE7ER

On Wed, Apr 17, 2019 at 07:49 PM, Adrian Chadd wrote:
Honestly though, if we had an ALC input to drive low to decrease TX gain and thus output, we could create our own power control loopbacks and SWR protection. It'd make 100W operation less.. crazy.
 
(I'd like to do this, but I'm still diagnosing the basics on the v4 board; I'd like the TX drive out to be clean before i feed it into an amp and waste more power..)
 
 
-adrian

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