<HTML>Dennis, this is not likely to be a standard part you can just buy or trade for. You'll need to either contact an avionics shop to make one for you, or you'll have to go to an electrical/radio supply house and purchase sufficient RG-58U and the appropriate end-connectors (most likely BNC types.) You could start out by measuring the length you need, and call Aircraft Spruce and Specialty (877/477-7823) to order the cable. (PN RG-58AU at 24 cents per foot.) They can help you with the connectors as well.</HTML>
<HTML>I'm not sure why, but I believe I recall reading somewhere that RG-58A/U is no longer suitable for installation in certificated airplanes.
When I upgraded the instrument panel in my '63 172 last year, the FSDO inspector insisted that any new coax installed be RG-400/U. The original avionics antenna cables (installed in 1963) were all RG-58A/U, but some time between then and now, the FAA decided that RG-400/U had to be used. Funny thing is, they both have the same impedance (50 ohms), the same outside diameter (.195"), and nearly the same center conductor diameter (RG-58A/U is 19 strand .0071" and RG-400/U is 19 strand .0077"), but RG-58A/U uses poly dielectric and cover whereas RG-400/U uses Teflon dielectric and cover, and while RG-58A/U has a single braid shield, RG-400/U has a double braid shield.
Oh, and one other thing: RG-400/U is nearly $2.00 per foot, while RG-58A/U is $.24 per foot!
The only thing I can think of for the change is that Teflon is more fire retardant than poly, and the double braid is less "leaky" (R.F. wise) than the single braid.</HTML>
<HTML>I'm not an expert, but I believe rg400/u is required for certain applications now. I recently upgraded some avionics, but don't recall if this high dollar coax is required for everything, or just transmission antennas, such as com, transponder, etc. In additon to less RF loss, RG400/u may be less toxic (cyanide release) during meltdown (fire). Any decent avionics shop can answer this with just a phone call, as well as being able to make the cable for a nominal cost.</HTML>
<HTML>RG-400U meets new specifications for coaxial radio installations. If you are making a new installation and meeting TSO requirements of a particular installation,...Or simply wanting the latest standards for your coax,...then RG-400U is the stuff to use as it meets later fire standards. Since Dennis was apparently simply replacing an existing (older) cable, then using the exact replacement part (RG-58A/U) seemed appropriate and is certainly less expensive. No argument from me that RG-400U is a higher grade material,....although not from a performance standpoint,...only from an onboard fire standpoint. (Although I'm not sure how a 1/4 inch diameter cable located in the tailcone of a 150 poses such a hazard.)
But it's a good and valid point that Stan and "empire" make.</HTML>
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