[RTTY] AFSK Splatter

[Joe Subich, W4TV]

> Andy Swiffin, GM8EOG wrote: 
>
> There is one area where clipping occurs which caught me out, and I
> didn't spot it as a problem until I started using PSK.
> 
> This is in the audio stage _before_ the mic gain.  I had been using
> rtty afsk for a while with no bad reports (everyone too kind?) but 
> when I started using PSK I was getting bad IMD reports.  The rig 
> (TS830) was not showing any ALC and even when I reduced power using 
> the Mic gain IMD was still bad.  

This is another reason to insert AFSK and PSK audio at the Accessory 
jack instead of the microphone jack.  With most radios, the Accessory 
input is after the microphone preamplifier and requires about 20 dB 
more drive.  Many radios automatically defeat the transmitter audio 
compression and clipping circuits when the accessory input is used. 
Finally, the higher level makes the accessory input more resistant 
to RF feedback.  

73, 

    ... Joe, W4TV