[Coco] Re: [Color Computer] Is this a discussion about a new Coco?

[j_e_daggett]

--- In ColorComputer at yahoogroups.com, "James Diffendaffer"
<jdiffendaffer at y...> wrote:
 
> > I am also very well aware of what the equiptment
> > needed to test will cost.  You can figure $2500 easily to have a board
> > tested at a lab.
> 
> That is way cheaper than what we were quoted.  There must be more
> competition now and the change to the approval process probably helped. 
>
*********

Local Universities are a nice source for stuff like this. Large
companies tend to help in the funding to get a price break on the
testing. Private labs  have far more overhead. 


> Any idea how much you have to pay the FCC for an approval these days?
> Just curious.
> 
> > to plunck down the cash to go to a certified testing facilities. If
> > you do proper board layout at the speeds the Coco runs at there is
> > little chance of getting into major issues. 
> 
> Well, I'm a software engineer that knows dit about analog and RF. 
> Digital logic I can handle.
> 
*******

I am a Analog/RF engineer that dabbles in software on ocassions.

******* 
> I do remember if you don't have the shielding to an external Amiga
> drive properly grounded you can hear noise on an AM/FM radio a good 15
> ft or more away.  Especially when the length of  the cable was about
> the length of an AIR drive cable. 
> Anyone with an AIR drive can verify this if they want... NONE of the
> AIR drives have the cable shielding attached to ground.
******* 

The biggest radiation from external computing devices is the cabling.
That nice ribbon cable from the computer to the external device is
radiation just waiting to happen. IF you cut it at the right length, 
it can tear up the FM band very quickly. Generally speaking the faster
the clock lines are and the greater the impeadance mismatch between
the source and load the greater chances for cabling to radiate. I have
also found the the low order address lines tend to radiate more than
the higher order bits. A0 and A1 lines tend to be real noisy. They
tend to switch more often. 

james






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