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Re: [TowerTalk] Castastrophic Consequences of Connector Failure?

To: Pat Barthelow <>
Subject: Re: [TowerTalk] Castastrophic Consequences of Connector Failure?
From: John Elsik <>
Date: Wed, 21 May 2008 13:32:59 -0600
List-post: <">>
Check out the Telepost Inc. LP-100A digital Wattmeter.
It has user settable SWR alarm points that will open a PTT line to the 
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.

> Date: Wed, 21 May 2008 11:16:24 -0400> From:> To: 
>> CC:> 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 k
 now 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, o
 r 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)> 
_______________________________________________> > > > 
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