In article <2269@cs.Buffalo.EDU> bowen@cs.Buffalo.EDU (Devon E Bowen) writes: >With all this discussion of ethernet being used as coax, I'm wondering >about the cable numbering system. Can someone give a brief explanation of >the differences in coax types (like RG8U, etc) and their characteristics? > Got out the Belden catalog. Far as I know, the RG numbers look random. Probably assigned by a clerk in the Pentagon during WW2. (call Belden at 800-BELDEN1 and ask for a catalog) Below is a short table of the various coaxes and the more important characteristics. RG# impedence attenuation 50Mhz per 100' velocity max voltage RMSkv RG6U 75 1.5 dB 78% (foam) 0.6kv RG8U 52 1.2 66 (polyethlene) 5kv RG8U 50 1.1 78 (foam) 0.6 RG11U 75 1.3 66 (poly) 5 RG11U 75 1.0 78 (foam) 0.6 RG58U 53 3.1 66 (poly) 1.9kv RG58U 50 3.2 78 (foam) 0.2kv RG59U 73 2.4 66 (poly) 2.3 RG62U 93 1.9 84 (air & poly) 0.7kv RG59U 75 2.1 78 (foam) 0.3kv RG71U 93 1.9 84 (air & poly) 0.7 RG122U 50 4.5 66 (poly) 1.9 RG141U 50 2.1 69 (teflon) 1.9 RG142U 50 2.7 69 " 1.9 RG178U 50 10.5 69 " 1.0 RG179U 75 8.5 69 " 1.2 RG180U 95 4.6 69 " 1.5 RG187U 75 8.5 69 " 1.2 RG188U 50 9.6 69 " 1.2 RG196U 50 10.5 69 " 1.2 RG303U 50 2.1 69 " 1.9 RG316U 50 9.4 69 " 1.2 RG174U 50 6.6 66 (poly) 1.5 RG213U 50 1.6 66 " 5 RG214U 50 1.6 66 " 5 RG223U 50 3.1 66 " 1.9 RG9U 51 1.6 66 " 5 ethernet 50 1.2 78 (foam) 0.6 22B/U 95 2.1 twisted pair 66 (poly) ? twin lead 300 0.8 (worse when wet!) 80 (poly) ? these are all the RG#'s I found. The attenuation curves generally follow a straight line when drawn on log-log graph paper. The slope is such that a coax with 2dB at 50Mhz will be 0.8 at 10Mhz. Most coaxes have about the same slope. So, one need only look at the same freq when comparing attenuations when selecting which coax you're gonna use from under the shack table (not strictly true, but close enough for "goverment" work! :-) ). Voltage ratings: note that foam dielectric cannot take as much voltage as solid dielectric. 73 de WA2ISE (I tried posting this when the virus happened, and it turns out that we had a failure of the UUCP connection at about the same time. Don't know if this posting ever made it out to the outside world, so my apologies if this posting turns out to be redundant.)