On 4/24/2012 8:07 PM, Don Wilhelm wrote: > Below 100 MHz, the UHF connector is perfectly adequate.
The notion that PL-259 and mating SO239 connectors are not good at VHF (and even low UHF) because their impedance isn't close enough to 50 ohms is one of those myths that is not based on fact. A few years ago, I spliced together 1,300 ft of Commscope 3227 (like LMR400, but with a solid #10 copper center) that cut into 100 ft lengths for a DX trip. There were a total of about 24 PL-259s and about half that number of barrels, all Amphenols. The loss at 500 MHz measured by substitution using HP test gear, was a dB or so less than the published spec for the cable. What folks seem to miss is that 1) while there may be a SMALL difference in the Zo, the length of the connector is also small as a fraction of a wavelength, and 2) the tendency of loss in ANY transmission line to bring the VSWR back to unity. Both of these factors tend to render any small discontinuity meaningless below 1 GHz or so. What matters FAR more is the QUALITY of the connectors used. Most of the deficiencies blamed on UHF connectors (and on BNC connectors) are the result of the use of no-name JUNK connectors. I use nothing but Amphenols. They cost a bit more, but I've been bitten far too often (and badly) when I've used anything else. Nothing like having a connector fall apart, or melt because it's made of thin metal, or because wide tolerance parts don't mate securely, or a dielectric that melts when you try to solder the connector. And a junk connector that fails 80 ft up in the air can be both difficult to diagnose and VERY costly to replace! 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
