Allan, That's a good question! Both "N" and "BNC" connectors vary the dielectric thickness, and the spacing and diameter of the center and shield elements, so that the swept impedance seen by a Time-Domain Spectrometer (TDR Test Set) shows no variation in characteristic impedance through the connector. When a "Constant-Impedance" connector is installed <CORRECTLY> in a transmission line, its presence will not be revealed when swept with a TDR Test Set.
The infamous PL-259 plug, when mated with the matching SO-239 jack, is far from constant impedance. Even the most basic TDR Test Set can detect the impedance "bump" where UHF connectors are used. Where the impedance is not constant, unwanted parasitic oscillations can occur, which means that intermodulation and spurious signals have a fertile breeding ground. Moreover, the ideal RF transmission system comprises cable and connectors that present a uniform 50-ohm impedance, without any significant bumps or dips. This cannot be achieved with RF connectors that do not have constant impedance. 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of allan crites Sent: Thursday, March 22, 2007 7:57 PM To: [email protected] Subject: RE: [Repeater-Builder] LMR feedline revisited and revised! I sure would like to hear what you all mean by " constant impedance ". Allan Crites, WA9ZZU
