I was dumping 900 watts of RF into a dummy load, but I wanted to see it on an oscilloscope so I got out my trusty homebrew line section and put it in. It's nothing but an aluminum project box with UHF jacks on the ends, a copper tube inside between them, and a BNC on one side connected to an AWG 14 wire going in and running parallel to the copper tubing. After 10 minutes I killed the RF and pulled out the line section and set it aside. A few days later I saw the line section on a table and noticed one of the UHF jacks looked odd. Upon inspection the dielectric looked carbonized, and the opposite end jack was starting to show signs of heat stress as well. Let's take a look at an assortment of jacks to see what happened. First are the bad jacks. These were once nice pretty items for sale at some hamfest. They appeared to have silver plating, Teflon dielectric, and pin cups that appeared to be gold plated. They looked great sitting in a bin on a vendor's table at a hamfest. What could go wrong? In reality these were poor off-shore junk. Now the jacks wearing white hats: On the left is a genuine Amphenol jack. You can't go wrong with this one. It's dielectric is PBT polyester, and it's nickel plated zinc and takes solder easily, but it is machined perfectly to mate with a UHF plug, and the pin cup has four fingers that really grip the plug pin. It will handle power indefinitely or at least, indefinitely in ham time. The Teflon dielectric jacks are made off-shore and closely resemble the bad jacks, but look closely and you'll see that the pin cup inner diameter isn't quite as wide, allowing them to also make fairly good pin contact (but I'm throwing them out anyway because fairly good isn't good enough). In the case of the bad jacks, what happened is that the machining of the pin cup was so sloppy and inferior that it didn't grip at all. I put a plug in one without screwing on the collar, and held the assembly vertically with the jack facing down and watched the plug fall out and hit the floor. Amphenol jacks provide such a tight grip they easily pass this test. A poor grip of course means resistance, which means heat, and after 10 minutes of continuous RF, that means a carbonized dielectric. I learned my lesson and have been going through the irritating process of rooting out the bad jacks in my homebrew gear and replacing them with Amphenols. The next time you are at a hamfest and see the nice pretty and inexpensive jacks, think twice. At least, carry a UHF male with you to check the seating of the pin in the females before purchase.