I think I will continue to use crimps and proper rubber seal wrap .
>From: Burt Lang <[EMAIL PROTECTED]> >Reply-To: [email protected] >To: [email protected] >Subject: Re: [Repeater-Builder] LMR feedline revisited and revised! >Date: Fri, 23 Mar 2007 01:12:41 -0400 > >Hi folks > >I have heard that the military will not allow BNCs on RF connections >because the bayonet connection on the outside shell allows the ground >side of the cable to vary (wiggle) and be noisy. BNCs appear to be used >for data and low freq but TNCs are specified for RF use. > >Some years ago a local club was having trouble with their homebuilt >duplexor that used BNC connectors on the cable connections. The >duplexor became noisy intermittantly. Move the cables and it would >quiet down for a few days but would always return. I suppled them with >equivalent TNC connectors for the duplexor and they never had trouble >again from that source. > >The standard PL259/SO239 combo has an impedance of approximately 35 >ohms. If the insulation is removed from the SO239, the impedance is >close to 50 ohms. I did see a Japanese wattmeter (I think it was Yaesu) >that had insulatorless SO239s on it. > >One problem with the PL259 that I have not seen mentioned is that it is >not weatherproof and the ground connection is problematic at best. It is >very easy to tighten the shell and then find it loose because the >"teeth" on the PL259 were not bottomed into the notches in the SO-239. > >Just my 2c for what it is worth. > >Burt VE2BMQ>> > >Eric Lemmon wrote: > > 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 > > > > _________________________________________________________________ Advertisement: Its simple! Sell your car for just $20 at carsales.com.au http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fsecure%2Dau%2Eimrworldwide%2Ecom%2Fcgi%2Dbin%2Fa%2Fci%5F450304%2Fet%5F2%2Fcg%5F801577%2Fpi%5F1005244%2Fai%5F838588&_t=754951090&_r=tig&_m=EXT
