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ADC Clip when Transmitting

Jim Fuller
 

Hardware: FDM-DUO with DUO-ART.

Maybe I have just noticed it, but whenever I transmit the red ADC clip indicator on SW2 comes on. Also the "PK" on the FDM DUO starts flashing. I have made both SSB and digital contacts under these conditions. Checked and it still happens at .1W output. My QTH is a pretty quiet environment so the lights never come on in receive mode.

Has anyone else seen this?

If not any idea as to the cause?

Jim - KC4JNW

Thomas McQuiggan <m7mcqio83ro@...>
 

Hi Jim, it's strange that you should post this message, because I was JUST about to post the same question! When I transmit (FDM DUO & DUO-ART), I see the PK light come on and it stays on for a few seconds after I stop transmitting. No idea why.

Tom - M7MCQ

David
 

Can confirm that the red ADC clip indicator comes up on my SW2 PC display when transmitting on my FDM-DUO.  I’ve had my FDM-DUO for around 4 years, but didn’t notice anything until May, when I’d hardly used it for 2 years because I’d being using an IC7300.  

Sole rig is now FDM-DUO + ART120.

I’m clearly not very observant, because I didn’t notice that the PK indicator was also flashing until Jim reported it!

Both indicators are suppressed on transmit if the receive Attenuator is active.  Indicators do not come up on receive whether or not attenuator active.  Short, screened usb leads in use and all leads have clip on ferrites.


David.   G8IIC


On 21 Nov 2019, at 15:11, Thomas McQuiggan <m7mcqio83ro@...> wrote:

Hi Jim, it's strange that you should post this message, because I was JUST about to post the same question! When I transmit (FDM DUO & DUO-ART), I see the PK light come on and it stays on for a few seconds after I stop transmitting. No idea why.

Tom - M7MCQ

Neil Smith G4DBN
 

Totally expected behaviour as the radio is full duplex, so when you are not using the attenuator, you will see some peaks above the -10dBm overload level.  It certainly does it on the 0dBm output. The indicators stay active for a while after being triggered.

It isn't anything to worry about, you can always set DUO Menu 50 ATT ON TX to "ON" to stop it if you don't mind the additional clicking of the attenuator relay on PTT.

Neil G4DBN

On 21/11/2019 16:01, David via Groups.Io wrote:
Can confirm that the red ADC clip indicator comes up on my SW2 PC display when transmitting on my FDM-DUO.  I’ve had my FDM-DUO for around 4 years, but didn’t notice anything until May, when I’d hardly used it for 2 years because I’d being using an IC7300.  

Sole rig is now FDM-DUO + ART120.

I’m clearly not very observant, because I didn’t notice that the PK indicator was also flashing until Jim reported it!

Both indicators are suppressed on transmit if the receive Attenuator is active.  Indicators do not come up on receive whether or not attenuator active.  Short, screened usb leads in use and all leads have clip on ferrites.


David.   G8IIC


On 21 Nov 2019, at 15:11, Thomas McQuiggan <m7mcqio83ro@...> wrote:

Hi Jim, it's strange that you should post this message, because I was JUST about to post the same question! When I transmit (FDM DUO & DUO-ART), I see the PK light come on and it stays on for a few seconds after I stop transmitting. No idea why.
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Thomas McQuiggan <m7mcqio83ro@...>
 

Thanks Neil. Another great response.

Tom

Jim Fuller
 

Thanks - I just got my ART back after repairs so I am questioning anything that appears different.

Jim - KC4JNW

David
 

Thanks, Neil.

David

On 22 Nov 2019, at 12:01, Jim Fuller <jfull550@...> wrote:

Thanks - I just got my ART back after repairs so I am questioning anything that appears different.

Jim - KC4JNW