[TenTec] Audio Hum on Omni-VII

[Dudley Hurry]

Jim,

Could be, but not in all occasions..   Example, the Jupiter's audio 
output is isolated ground,  audio ground is not chassis ground,  
therefore you can not bond the audio ground to chassis ground,  
isolation or matching transformers is the only way to make a good audio 
connection.    This becomes a problem if you mix a Jupiter in with 
another brand radio using a common ground switch.     Not sure what 
laptop you are using, but some are running above ground,  there might 
not even be a ground on the power supply,  and some don't take kindly 
being grounded in the wrong place due to the switching powersupply.   
Try this,  take a voltmeter and check the laptop metal ground to your 
station ground,  you might be surprised at what you find.. 

I use a Furman Isolation panel to help here in my shack.. 


73,
Dudley

WA5QPZ



Jim Brown K9YC wrote:
> On Wed, 17 Sep 2008 22:32:00 -0500, Dudley Hurry wrote:
>
>   
>> You have a ground loop to the laptop..  I bet that you will lose the hum 
>> if you break the ground from the radio to/from the laptop sound card..   
>> Better isolation from the radio to the sound card.  
>>     
>
>   
>> You might even try an extra ground from the laptop to station ground,  
>> but it is most likely a audio loop,  isolation transformers should take 
>> care of it.. 
>>     
>
> I'm an audio systems design consultant and consultant on EMC in audio 
> systems (that is, hum, buzz, and RFI). There is much misunderstanding 
> about the unbalanced interconnection of ham gear. Much of what is written 
> about it is WRONG, including in some ARRL publications. You do NOT need 
> "isolation," you need simple BONDING between the laptop and the radio. 
>
> To see what's REALLY going on with your hum and buzz, and to fix your 
> problems without a transformer and using nothing more than plain ordinary 
> copper wire, see 
>
> http://audiosystemsgroup.com/HamInterfacing.pdf 
>
> and the Chapter on Solving Problems in the Shack in 
>
> http://audiosystemsgroup.com/RFI-Ham.pdf
>
> 73,
>
> Jim Brown K9YC
> Audio Systems Group, Inc. 
> Chair -- AES Technical Committee on EMC
>
>
>
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