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Re: FDC cableing



Hi Joe,
	I think that should be fine from an electrical point of view. The drain 
wire is certainly needed to make good contact with the foil shield. The 
braid, is maybe more for mechanical protection than anything else. Since 
we're not pulling the cable through pipes (right?) I would think it is 
probably redundant.
	For any changes that affect the electrical performance of the cable, 
i.e., I think we can safely exclude the jacket color and thickness - but 
braided or not, and type of dielectric (PVC or other) can certainly make 
a difference, for any such changes I really hope that the first cables 
we get already have the intended final design. I will need to make 
measurements on them and tune the ADC board to compensate for the cable 
losses, and of course we'll be using these first cables for the full 
scale prototype tests. I'm sure you had this in mind already, but I'm 
mentioning it anyway.
	Thanks,

	Gerard

p.s. I do have that 20-pair halogen-free sample still. I can probably 
set up a test to see how much (if any) difference it makes to have the 
braid or only the foil shielding the cable. As I said I bet the 
difference is small, but let me try it out. Don't wait for me though!


Joe Beaufait wrote:
> I am glad we have decided to go ahead and purchase a sample of the 25 
> pr. cable. This cable is going to be the standard for much of the data 
> acquisition system and it would be very nice to see how hard it is to 
> work with.
> 
> On that note, there were some comments made at the Wednesday FDC meeting 
>  concerning the possible redesign of the cable. Daniel mentioned that we 
> might ask to make the outer jacket thiner and I promised to look into it 
> but, while looking at the cable diagram I also noticed that this cable 
> is double shielded. It has an aluminized mylar layer with drain wire, 
> and a copper braid. I believe we could do away with the copper braid and 
> reduce the copper in the cable by at least half.
> 
> I would like comments from the group on whether or not you would like me 
>  to pursue this.
> 
> Thanks
> Joe
>