[eagle] Re: 70 cm Receiver IF Spurs - Problem Solved

Juan Rivera juan-rivera at sbcglobal.net
Sun Jun 17 11:06:45 PDT 2007


Chuck,

I don't want to tear into the CAN-Do module.  I feel like it is a loaner and
not mine to modify.  It would be interesting to disconnect the switch and
the current monitor from the CAN-Do power input and move it to those user
pins as you suggest.  That might just work, but I also know they don't want
to have multiple versions of the module floating around and this would be
one.

We also can't loose sight of the radiated noise from that inductor.  I can
see signs of EMI if it gets within 2 inches of the sensitive areas of the
receiver.

73,

Juan


73,

Juan

-----Original Message-----
From: Chuck Green [mailto:greencl at mindspring.com] 
Sent: Sunday, June 17, 2007 9:18 AM
To: juan-rivera at sbcglobal.net
Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved

Hi Juan,

I am impressed with your testing and analysis. 

I find it curious that you were unable to filter the power from the 
CAN-Do! .  But switching noise is notorious for being difficult to 
filter.  So maybe that is something to just forget. But in a total 
system (satellite) it may not be possible to forget.  We may need to 
find a way to filter the power for sensitive modules even if not using 
power from the CAN-Do! ; in which case, such a filter may also filter 
the noise from the CAN-Do! .

If your analysis is correct, and it certainly seems to be, then it would 
also seem possible to remove the switch from the CAN-Do! (not just 
bypass it) and rout your clean power source through the CAN-Do! current 
measurement circuit thus saving having to do this in the module.

Great work!  And thanks.

Chuck



Juan Rivera wrote:
> Hi Chuck,
>
> Bad news I'm afraid.  See my report for details...  I've sent out a link
to
> the group.
>
> 73,
>
> Juan
>
> -----Original Message-----
> From: Chuck Green [mailto:greencl at mindspring.com] 
> Sent: Saturday, June 16, 2007 8:57 AM
> To: juan-rivera at sbcglobal.net
> Cc: eagle at amsat.org; David Smith; Dave Black (Work); Dave Black (Home);
> Samsonoff at Mac. Com; Juan.Rivera (Work)
> Subject: Re: [eagle] 70 cm Receiver IF Spurs - Problem Solved
>
> Hi Juan,
>
> This is fantastic! 
>
> Please try one more experiment.  Pass the module current through the 
> current measuring circuit on the CAN-Do! while bypassing the switch 
> transistor (you could just short across the switch transistor) and see 
> if the problem reappears. 
>
> If you end up having to use the user pins, you will need to add current 
> measuring circuitry to your module.  While this is no big deal, its one 
> more thing you might not have to do.
>
> Chuck
>
> Juan Rivera wrote:
>   
>> All,
>>
>>  
>>
>> The 70 cm Receiver spur problem has been solved.  Click here 
>>
>>     
>
<http://www.juanr.com/pages/hobbies/ham_radio/Eagle/CAN-Do_Noise_Troubleshoo
> ting.htm> 
>   
>> for details.
>>
>>  
>>
>> 73,
>>
>>  
>>
>> Juan
>>
>> WA6HTP
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Via the Eagle mailing list courtesy of AMSAT-NA
>> Eagle at amsat.org
>> http://amsat.org/mailman/listinfo/eagle
>>   
>>     
>
>
>
>   




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