Somewhat deaf D4D


Dr. Pedro E. Colla (LU7DID)
 

Hello,

I've been using the D4D as part of my FT8/WSPR beacon and monitoring station for several months now, very good performance I must say.

However, recently, it stopped working.

It was not able to either transmit nor receive. Replacing the NE602 restored transmission back to life, and reception is working as well.

Transmission chain seems to be Ok. monitoring the signal yield a strong level, or at least compatible with what used to be.

However testing the reception it's able to hear and decode another transmitter at the shack in FT8 with only 4 dB SNR (normal yield should be more like 15 dB), and in fact isn't hearing anything else, even strong signals present in the band.

Any suggestion on a trace and/or test to perform in order to identify which other component might be operating in a faulty way?

Thanks in advance, Pedro, LU7DID


Adam Rong
 

Hi Dr. Pedro,

Please measure relay contacts with ohm meter. Also, please short the crystal in front end with a 103 or 104 cap to see if it improves. Also please check the contact of the audio out jack and cable.

Thanks,
Adam

在 2020年4月12日,上午2:21,Dr. Pedro E. Colla (LU7DID) <lu7did@...> 写道:

Hello,

I've been using the D4D as part of my FT8/WSPR beacon and monitoring station for several months now, very good performance I must say.

However, recently, it stopped working.

It was not able to either transmit nor receive. Replacing the NE602 restored transmission back to life, and reception is working as well.

Transmission chain seems to be Ok. monitoring the signal yield a strong level, or at least compatible with what used to be.

However testing the reception it's able to hear and decode another transmitter at the shack in FT8 with only 4 dB SNR (normal yield should be more like 15 dB), and in fact isn't hearing anything else, even strong signals present in the band.

Any suggestion on a trace and/or test to perform in order to identify which other component might be operating in a faulty way?

Thanks in advance, Pedro, LU7DID


Dr. Pedro E. Colla (LU7DID)
 

Hi Adam,

Thank you for your kind reply.

Relay seems to be good. Will try during the afternoon the other two tips.

73 de Pedro, LU7DID


Dr. Pedro E. Colla (LU7DID)
 

Hi Adam,

Short circuiting X1 did it. The receiver is back to life with the usual performance.

Regards, Pedro LU7DID