[Ham-Mac] CI-V interface noise

[Don Agro]

Hi Chris,

On 15-Apr-07, at 4:03 PM, EZ Rhino wrote:

> This is driving me bonkers.  There has got to be someone else on  
> this list with this problem besides me.
>
> Problem:  When I connect my iMac to my Icom 746pro (USB from  
> computer to "data" port on radio), I get a LOT of noise appear in  
> the radio.
>
> Equipment:  PowerPC iMac, running Tiger.  MicroHam USB interface  
> II.  Icom 746pro.  I use MacLoggerDX and CocoaModem.
>
> Specifics:  Click the "Radio VFO" box on MLDX, and the noise  
> appears. Click it again and the noise goes away.  It is worst  
> (unacceptable) on 15 meters;  also present on 20m and 17m.   Before  
> I went to my current interface (MicroHam) I was using a Black Cat  
> USB Ci-V interface with the same problem, but it wasn't as noisy as  
> my current interface.  I mostly solved the problem before by  
> wrapping the USB cable from the computer through a large toroid.   
> (transformer E core, to be precise.)  When I put the MicroHam  
> interface on, I put an additional E core on the cable, and still  
> can't reduce the noise to what I consider acceptable levels.  I've  
> tried grounding the iMac, grounding the interface, etc. to no  
> avail. (Where the heck are you supposed to ground an iMac anyways?  
> I pulled the back cover off and attached a braid to a case  
> screw.)   I am annoyed that using interfaces with supposed  
> "isolation" still doesn't eliminate the noise.  Anyone have any  
> suggestions for something I haven't already tried?
>
> Thanks in advance,
>
> Chris
> KF7P

I know this probably isn't going to be of much help to you - but the  
only two times I have had noise problems on HF they have been due to  
a terminally ill power supply in my older MDD PPC desktop Mac.

I have replaced the power supply twice and will probably have to do  
it again (design flaw). The HF noise serves as an 'early warning'  
system for me that the power supply is going.

What I am suggesting is the possibility that the noise may be  
originating in the iMac switching power supply and the USB/CI-V is  
just acting as an electrical conduit ?


73 Don Agro VE3VRW

D o g   P a r k   S o f t w a r e   L t d .

email: dagro at dogparksoftware.com
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