[eagle] Re: CAN-Do noise problem is proving to be a difficult one to fix

Jim Sanford wb4gcs at amsat.org
Fri Jun 15 14:16:08 PDT 2007


Juan:
My thoughts:
1.  We must stop the radiated noise.  Let's try obtaining and placing a 
shielded inductor on the CAN-Do! module.
2.  I just read a great suggestion from Lou, amplified by a phone call I 
just had with Rick, regarding three terminal filter devices.  Seems like 
a good start.
3.  I agree that we need to review the bidding on packaging.  That will 
probably be the LAST of these issues we take on.

Thanks & 73,
Jim
wb4gcs at amsat.org


Juan Rivera wrote:

> All,
>
>  
>
> Please see my write-up here 
> <http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshooting.htm>.
>
>  
>
> The CAN-Do noise is not lending itself to an easy cure.  I think this 
> whole subject of RFI/EMI needs to be looked at closely.  Every payload 
> will be affected by noise on its inputs and can affect other payloads 
> by creating noise that is propagated back out from within its module 
> chassis.
>
>  
>
> With the current scheme, of having a CAN-Do module located in the same 
> case as the main payload, there are several issues that need immediate 
> attention:
>
>  
>
> 1)    The CAN-Do module provides dirty power - both the +13 VDC output 
> and the ground are noisy
>
> 2)    The CAN-Do's switching power supply inductor, L3, radiates noise 
> that can affect sensitive circuits several inches away.
>
>  
>
> Both of these factors are adversely impacting the 70 cm breadboard 
> receiver in the form of 5 kHz spurs on the IF output.  As I mentions 
> earlier, Rather than work to clean up the CAN-Do module immediately, 
> we should focus on making the receiver function In the presence of 
> this noise.  This approach will result in a more robust design.  The 
> CAN-Do module needs to be cleaned up, but for now it acts as a great 
> real-world noise generator.
>
>  
>
> I'm currently out of ideas.  I'd like to hear what you all have to say.
>
>  
>
> 73,
>
>  
>
> Juan
>
> WA6HTP
>
>------------------------------------------------------------------------
>
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>  
>
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