[DSP-10] microphonics !!! and noise pickup

[dsp-10@mailman.qth.net]

In a message dated 2/28/02 6:50:26 AM Pacific Standard Time, 
cupido@mail.ua.pt writes:


> Also I have quite a large pickup of digital noise, that is comming
> from the DAC out connections to the RF board. Noise that seems
> to exist in the EZKIT already... So looks that is nothing we can do
> about this ...  Any idea.
> 

I had a similar problem. I solved it by reworking the cabling INSIDE the 
EZLite box. My noise was RS-232 based data induced noise. I routed the ADC 
and DAC cables to the far(I'll call it North, nearest the J2 J3 end). Each 
DAC/ADC conductor is the inside of a small mini coax. the outer shield is 
soldered at the copper box very close to the feed thru. Total of 6 I think, 2 
conductor and 1 return each.

I also did the same thing with the RS-232 cabling, running the digital signal 
as the inner conductor of a mini coax and the outer shield connected at the 
copper box. This cable bundle(4 I think) runs thru the center/south center of 
the ezlite board, staying as far away from the ADC/DAC circuits as possible. 
The control FL0, etc lines are in small teflon on the (South) end of the 
board.

Replaced the RS-232 from the EZlite box to the outer DB9 connector with mini 
coax in similar fashion.

Got rid of the "zing" I could hear with each data burst from the DSP-10.

Hope this helps, Cheers

de Phil

KF8JW


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