Hi guys, some practical comments: * 50 Ohms transmission lines are much easier to fabricate on standard 4, 6, or 8 layer PCB's. 75 Ohms traces are very thin and thus have issues in manufacturing accuracy. * Feeding a 50 Ohm source into a 75 Ohm load gives a VSWR of 1.5, a mismatch loss of only 0.177dBm, and a return loss of -13.98dBm, so not much power is lost due to the mismatch loss. Of course at high power the -14dB return is a problem. * 50 Ohm connectors are mechanically more stable and easier to manufacture. 75 Ohm BNC for example removes the internal dielectric and leaves the center pins "floating" in free air so they can break more easily. * 75 Ohms requires thicker dielectrics, or higher dk dielectrics - tougher to manufacture. * 75 Ohms cables usually use dirt-cheap and flaky F-connectors. These get jammed easily, and every F-Connector I have seen so far has a different center pin length. Whoever designed F-Connectors (and S-Video connectors!!) should be held accountable in my opinion. There are so many better ways to design a (cost-effective) connection. bye, Said
************************************** See what's free at http://www.aol.com. _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
