Rx audio crashes with DNF

Denny WB8K

Found an interesting 'bug' or maybe a safety feature. Ftdx101MP with original software (V01-14)
Noticed on 160 meters but duplicated on all bands. With radio set on Ant = IPO, Att=Off,  AGC=Off and DNF=on and set to level 1.
With no antenna, all is fine but when switching to an active antenna (Inverted L on 160) the rx audio stops, no audio at all. All other display items are normal. The only way I could get rx audio back to normal was
to turn the radio off and then back on again. So, is this a bug with the DNF =on or some  safety feature to protect the radio from an overload of sorts? I also noted that this happens if a loud static crash with the DNF on .
Denny - WB8K

Lou W7HV

Perhaps related, but DNR level 1 caused very bad distortion on big CW sigs with 202004.  202104 fixed it, and I find DNR to work much better overall on CW.  With 202004, I just didn't use it as it distorted the CW signal too much.  Now I find it quite useful and often using it at level 6 or 8 on CW.

Rejean Leveille

AGC OFF depending the signal + noise floor, this is possible to overload the SDR receiver and going to a lock-up situation not able to calculate. To be careful

AGC OFF only for very weak signals detection like below S-0  in CW mode. I did it for few occasions on 160 m with narrow APF with BOG + preamp.

Rejean, va2am

Lou W7HV

Seems like we're talking about two different things, the beneficial used of the RF Gain control and the rig locking up. The rig shouldn't lock up no matter, so that's a bug.  In my experimentation, AGC off too much RFG caused very bad distortion, but it never locked up, but IDK if that was done in conjunction with DNR level 1, which distorted on big CW sigs irrespective.

Turning down RFG also decreases the slope of the AGC, so in my experience turning it off may not be helpful anyway if you first turn down RFG. Generally, I listen to the band noise, and turn down RFG, turn on IPO and/or add attenuation if it's much bigger than the noise floor of the rig as heard with the antenna switched off.  IPO and atten work similarly in reducing the level of noise the RX has to deal with.  RFG then affects how it deals with what's there sig and noise wise.

Denny WB8K

Yes, RFG control is necessary with AGC=off otherwise there can be a large amount of distortion. Unfortunately when trying to optimize best s/n on a weak signal AGC= off and adjusting the RFG works better than AGC=on. The only problem with this is a loud static crash or a very loud signal can distort desired signal.  However this is not what I am concerned with. I just happened to note that with DNF= on and AGC=off the RX audio crashes wit a loud noise and then the radio must be reset to return to normal. This only happens with DNF=ON.
So far I have not found much benefit to using DNF so for now I leave it off.

Denny - WB8K