Re: D4D mods

Steven Weber

I would remove the diode in series with the 5V to the SA602. The minimum operating voltage for the SA602 is 4.5V and performance degrades quickly below 4.5V.



Thank you, Steve. Your diode mod is effective. In my test, the carrier leakage improved by about 5 dB, as a side effect, both USB and LSB signals increased about 1 dB which is a surprise to me. I also applied the BH4DCL diode mod, and it improved the carrier leakage further for another 3 dB, and there was no noticeable difference on the USB and LSB signal level.

I did try to change the emitter resistor from 1.5k to half and it won't help too much, so I will not change it.

So, my recommendation is that we apply both diode mods, hihi.





On Wed, Jul 31, 2019 at 4:36 AM Steven Weber <steve.kd1jv@...> wrote:

Yes, Q1’s collector should stay above 5V when 12_V is applied.




From: Adam Rong
Sent: Tuesday, July 30, 2019 10:33 AM
Subject: Re: [crkits] D4D mod


Hi Steve,

Thanks for your sharing. I will test them. One thing to confirm: If we add a diode between +5V and the collector of Q1, when 12V_R is present, the diode will be reverse biased? If not, I suppose it will mute the audio output.





Adam Rong


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