Will Martin <wmartin@STL-06SIMA.ARMY.MIL> (01/16/90)
>(While I was there in the store, a customer who was watching me look at >different kinds of cable told me that there was another type of cable >made by Belden which had two layers of shield, separated by an >insulator, and used both braid and foil; he said he used it at home, and >that it was very low-loss, and was commonly used for satellite downlinks >(which is what I am using this cable for). Unfortunately, he couldn't >remember the part number for the cable, and the people in the store had >never heard of it.) It would seem logical to start this sort of investigation, and to try to identify what that other person was referring to, by looking in the Belden catalog. While other wire companies have useful catalogs, none seem as comprehensive as Belden's, and I view it as sort of a reference handbook. You can get one by calling 1-800-BELDEN-4, or (317) 983-5200, or writing Belden at PO Box 1980, Richmond, IN 47375. (The reply card I have here also has an address for Belden's "Data Services Center" at PO Box 3064, Cedar Rapids, IA 52406; that may be somebody who processes these survey cards and not really be Belden, though.) There are also a number of regional sales offices in the US and worldwide, from which catalogs can be requested. The catalog lists a number of dual-shield coax cables, with both foil and braid. However, it appears that the types with insulation between the layers of shield are called "triaxial" instead of coax; I think the inner "shield" is actually used as a conductor instead of a shield in these applications, though I'm sure you can use it as a shield if you want. The things nearest to the description furnished are Belden 9232 or 9267. The percentage of shield coverage cited in the catalog is lower than some of the other multi-shield types, though I assume this is referring to using the middle layer as a conductor and not as a shield. It might come out far better when using both as shields. Hope this is of help. Regards, Will Martin