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

Chuck Green greencl at mindspring.com
Sun Jun 17 17:51:16 PDT 2007


Hi Juan,

One of the purposes of the CAN-Do! was to provide a standard interface 
so that a module couldn't do something nasty and take out the entire 
satellite.  So custom mods to the CAN-Do! are not allowed.  Having said 
that, we have always assumed that a jumper across the CAN-Do! power 
switch would be installed for those modules that needed to be powered up 
no-matter-what.

Chuck

Juan Rivera wrote:
> 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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