[TowerTalk] Castastrophic Consequences of Connector Failure?

[John Elsik]

Check out the Telepost Inc. LP-100A digital Wattmeter.
It has user settable SWR alarm points that will open a PTT line to the amplifier.
I think the Array Solutions version does this also, not sure.
I ordered a LP-100A this week.
I saw this feature as an added bonus to having a fancy wattmeter.
John
wa5zup



> Date: Wed, 21 May 2008 11:16:24 -0400> From: K8RI-on-TowerTalk at tm.net> To: aa6eg at hotmail.com> CC: towertalk at contesting.com> Subject: Re: [TowerTalk] Castastrophic Consequences of Connector Failure?> > Pat Barthelow wrote:> > Folks,> >> > When deciding on the reliability factor in your antenna construction, especially when running high power, or with modern solid state finals, I wonder what the probability of expensive damage is if an antenna connector, or adapter has a "hard" failure, i.e. an open or short circuit/flashover, etc. > This should be a concern even when using the best of connectors. Sooner > or later something in the feed line or antenna *will* fail. In Over the > last 10 years I've had a number of such failures. One, N type connector > shorted in the feed line to a center fed half wave sloper. The wire > between one side of a balun and another sloper broke at the balun > connector. There's no way to gracefully remove the old connector and > replace it. Don't know why it broke as there as a loop to take out > tension. These were hooked to a tuner and the output of the Alpha 76 > and 756 Pro. I had water get into a coax due to an abrasion in the > jacket. It was hanging in open space so I don't know what caused the > abrasion. That one was between a 40 meter, half wave, center fed sloper > and the Tokyo Hy-Power HL-1.5Kfx. SWR looked ok, but it'd give an > immediate shutdown due to SWR when much over 500 watts. I had the bees > get into the AV640 matching network, which caused high SWR shutdowns of > the HL-1.5Kfx and ruined about 6 or 8 feet of coax. And finally (as far > as I can remember "at the moment") the Hygain HDR-300 went past the > stops, tearing up the rotator loops to the tri-bander and the 7L 6-meter > Yagi.> > I have experienced few TX failures through the years, due to SWR faults caused by various antenna system faults. With a high power tube amp, I have heard of fatal damage inflicted to tubes, or to bandswitches, or output network components. On the other hand, I guess we can be lucky, and sometimes survive an antenna fault without damage to QRO active or passive path. > I don't know how many times I've heard an arc in either the tuner or > Alpha. Never any damage though.> > If the probability is high of expensive damage caused by antenna faults, perhaps it is worthwhile to achieve higher reliability by using higher quality and care with connector components.> > > That should be a given, but even with the best it's still going to > happen far more often than expected.> > Also, I often wondered that it might be a good widget to have a "trip relay" in an inline > In the old days it was not uncommon to see a "crowbar" using either an > SCR or relay to short the PS. The though of those shorting the PS always > bothered me, but they worked fine.> > meter accessory to quickly, but not instantaneously remove TX power under fault SWR occurances. I know Bird, has such in the commercial market. Is damage inflicted to the TX RF chain components by an antenna fault, usually quicker than a relay could remove/reduce RF power?> > > Many newer amps, both SS and tube, have protection circuitry built in. > To home brew it's time consuming and adds noticeably to the expense of > commercial amps, but is well worth it.> > 73> > Roger (K8RI)> _______________________________________________> > > > _______________________________________________> TowerTalk mailing list> TowerTalk at contesting.com> http://lists.contesting.com/mailman/listinfo/towertalk