Whats the logic for using DIGU instead of USB for FT8. If you use usb with a 4K filter you can see t

DIGU removes any transmit audio processing or shaping, providing a nice clean, flat response for your digital operation. In receive you can also use wider bandwidths - I use 5 kHz on HF.

I find the "wide graph" contained within the FT8 program to be much more useful in finding a free transmit frequency than attempting to use the SSDR screen.

Sorry, I didn’t see the earlier reply.

Al
DIGU / DIGL, and USB / LSB modes on a Flexradio, differ only in the fact that DIGU and DIGL modes bypass any, and all, DSP processing effects. You don't want any EQ-ing, or noise filtering being done on the signals your trying to decode. USB / LSB modes don't bypass those. Think of it as quick, convenient way to ensure that your sending unadulterated signals to the Digital Application your using. The choice is yours though, you can use USB / LSB and disable all the effects manually.

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Al

Also, the bandwidth filters are optimized for digital applications when using DIGU, they will either all use a 1500Hz center frequency or will be wide filters that start at 0 Hz and then go up to some useful upper cutoff point, like 3k or wider. Whereas USB filters are optimized for voice operations.

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