[eagle] Re: 70 cm Receiver Spur Source Found

Jim Sanford wb4gcs at amsat.org
Sun Jun 10 17:44:38 PDT 2007


Juan:
Can you "sniff" the various lines from CAN-Do! to get an idea of which 
is the source?

Also, my memory is that we still have an open issue with the passband 
ripple -- or did that get resolved and I missed it?

Again, thanks for all you're doing.

73,
Jim
wb4gcs at amsat.org


Juan Rivera wrote:

> All,
>
>  
>
> The source of the spurs in the 70 cm prototype receiver is the CAN-Do 
> module.
>
>  
>
> *This is the receiver IF output as designed*
>
> *(powered from pins 39 and 40 of the CAN-Do Module)*
>
>  
>
>  
>
> *This is the receiver running off of a separate power source*
>
> *(bypassing the CAN-Do Module +13 volt output on pins 39 and 40)*
>
> * *
>
>  
>
> *This is the same configuration as above, but with the CAN-Do module 
> shut down*
>
>  
>
> From the above it appears that:
>
>  
>
> 1.    The CAN-Do module is the source of all the spurs that I see
>
> 2.    None of the spurs are being generated by the receiver's internal 
> power supplies
>
> 3.    Some, but not all, of the noise is entering the receiver via the 
> switched +13 volt CAN-Do output on pins 39 and 40
>
> 4.    The remainder of the noise could be entering the receiver on 
> other CAN-Do pins, or being radiated to receiver components or traces 
> in close proximity
>
>  
>
> See my log for all the intermediate steps I took to reach these 
> conclusions.
>
>  
>
> Remaining RF issues:
>
>  
>
> 1.    Phase noise
>
> 2.    Microphonics
>
>  
>
> 73,
>
>  
>
> Juan
>
> WA6HTP
>
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