{Collins} Re: "Abjuer" ???



I think one of the best reasons for not using UHF series connectors lies not in its constant impedance properties, but in the fact that they are notorious intermod devils.  The dissimilar metals contribute to this, unless the Ag-plated versions are used, and even if assembled properly, the assembly process can be tough on the dielectric, unless one uses Teflon coax.  All in all, it think they are connectors to avoid, I convert all of my equipment to type N, or TNC.

Scott
---- John Painter <johnpainter@xxxxxxxxxxx> wrote: 
> Gentlemen (& any ladies present):
> 
> This ain't microwaves we're talking about.
> 
> That is, the question about how electrically good PL-259s and SO-239s are must consider the frequencies being used. I personally wouldn't use them above 30 Megacycles, but below that frequency, i.e.. in the HF bands, they are perfectly good electrically, in my opinion. And, my opinion is fairly well educated (300+ semester-hours of college. Yes, I was a slow learner :).
> 
> The "impedance" of a connector is not a lumped-component property. It is a transmission-line property. And, there are fairly simple equations by which the "impedance" of a connector (plug + socket) may be calculated. But, what we are really interested in is whether or not the plug/socket combination changes the impedance, looking into the transmission line (RG-58 or RG-8). And, the transmission-line equations can be manipulated to give us this answer, directly [1].
> 
> The change of impedance, going through the connector is a matter of how long it is, with respect to the wavelength. That length is measured in electrical degrees (phase shift). At 30-Megacycles, the electrical length of a 1-inch connector is 0.91 degrees or 0.016 radians. What this means at 30-Megacycles and below is that the PL-259/SO-239 connector combination, which is about 1-inch long, contributes no imaginary part to the characteristic impedance of the following 50-ohm transmission line. If the insulating material of the connector is Teflon, then its attenuation coefficient is alpha=0.00015, and the connector has absolutely no effect on the transmission-line impedance, seen through it. Even with the much lossier Plexiglas insulation (alpha~0.014), the effect is less than a tenth of a percent on the impedance seen. So, we don't have to worry about these connectors messing up the impedance of the transmission line at H.F.
> 
> Given that the PL-259/SO-239 combo is electrically OK at H.F., the argument comes down to its mechanical properties. My own opinion is that if a coax connector is going to be subject to stress, i.e.. a length of cable hanging on it, then the "UHF" connector set is the best we've got (for RG-8 and 9913), including Type-N. In my own VHF/UHF antenna installation, I have to go to great lengths to unstress the Type-N connectors, for the reason that Charlie has stated. But, for my HF antennas, I never worry about pulling the Type-UHF connectors apart. 
> 
> [1]. Reference Data for Radio Engineers - 4th Edition, ITT Corporation, 1956, pp. 67, 558.
> 
> John Painter
> W5LQS
> Stuck in the '50s.
> (There ain't been any decent music, since.)
> 
> ----- Original Message ----- 
> From: "Charlie" <pincon@xxxxxxxxx>
> To: <COLLINS@xxxxxxxxxxxxx>
> Sent: Tuesday, December 12, 2006 3:57 PM
> Subject: {Collins} "Abjuer" ???
> 
> 
> Sorry, I don't have the foggiest idea what "abjure" means, but I can guess 
> from the other words that I DO understand that you don't like UHF 
> connectors.
> 
> Why is this??  I have run 2 kW thru them from HF to 2 meters and never had a 
> problem.  (I do realize they create an impedance bump, so I hold my nose and 
> use N connectors on 220 and up.)   They're cheap, easy to install and will 
> take legal limit power, so what's the beef with them?  I disconnect all my 
> antennas when not in use in the summer, so the couple UHF connectors on the 
> HF antennas have been screwed on and off hundreds of times and they're fine.
> 
> Just curious....by the way, how do you keep the center pin from pulling out 
> of an "N" connector when there's any strain on the cable?  Never had that 
> problem with an PL-259 however.
> 
> 73' Charlie k3ICH
> 
> 
> ----- Original Message ----- 
> From: "Keith Carlsen" <kc21130@xxxxxxxxxxx>
> To: <COLLINS@xxxxxxxxxxxxx>
> Sent: Tuesday, December 12, 2006 12:24 AM
> Subject: {Collins} Re: Why no UHF connectors???
> 
> 
> >
> >
> >>A better question is:  Why Art had such a dislike of SO-239, UHF 
> >>connectors?   They jumped from the dinky "phono" connector to the overkill 
> >>"N" types, but NEVER an easy UHF connector.  I've heard some rumors about 
> >>some sort of conflict with the OEM Amphenol, but does anybody who the real 
> >>reason???
> >>
> >
> > I abjure, loathe and detest SO/PL-239s myself. Real radio equipment uses 
> > N's or BNC or TNCs! Including that coming out of Cedar Rapids today.
> >
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