Tiger Mountain (WA) master antenna catches on fire

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DaveSt
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Location: UK

Re: Tiger Mountain (WA) master antenna catches on fire

Post by DaveSt » Thu Nov 22, 2018 12:57 am

Failure of a single antenna in a 32 antenna system may not have have caused enough of a VSWR fault to cause a shut down anyway. Apart from that, VSWR protection may not be fast enough to detect arcing anyway.

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kkiddkkidd
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Re: Tiger Mountain (WA) master antenna catches on fire

Post by kkiddkkidd » Thu Nov 22, 2018 8:57 am

DaveSt wrote:
Thu Nov 22, 2018 12:57 am
Failure of a single antenna in a 32 antenna system may not have have caused enough of a VSWR fault to cause a shut down anyway. Apart from that, VSWR protection may not be fast enough to detect arcing anyway.
Interesting. I have exactly one client with combined antenna and it is a simple 2 station 6-bay ERI with less than 5kw total. It has a Bird Watcher on the output that seems to trigger on lightning strikes etc but has never had an antenna problem during my tenure.

Otherwise, I have _seen_ a few large combiners (Empire, Hancock and the big system in OKC) but never worked around them at all.

I had also incorrectly assumed that the radome material wasn't flammable but I guess it at least WAS moreso than I imagined.

Later,
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
http://www.kkbc.com

DaveSt
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Re: Tiger Mountain (WA) master antenna catches on fire

Post by DaveSt » Thu Nov 22, 2018 1:37 pm

kkiddkkidd wrote:
Thu Nov 22, 2018 8:57 am


I had also incorrectly assumed that the radome material wasn't flammable but I guess it at least WAS moreso than I imagined.
I was surprised to read that too. The radomes I see are invariably fibreglass and do not burn.

sallen
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Re: Tiger Mountain (WA) master antenna catches on fire

Post by sallen » Fri Nov 23, 2018 9:38 am

This was a dual feed antenna, a top and bottom section so there would have to been two VSWR detectors for each transmission line going up the tower to the antenna. Another question is why was there no pressure monitor on each transmission line along with a run monitor on the pressurization system. If I lost pressure on a large transmission line I would shut down the transmitter.

A better master antenna monitor system that not only looks at VSWR but line pressure, along with fire proof radomes, could have limited damage. Even if you can't get to the site for two hours, the immediate feed back from a good monitor system on the master antenna can still provide enough information to start to address the issue like turn off all the transmitters and go to the backup site. ERI pretty much admits this in the article.

Looks like between ATC and ERI they have some humble pie for Thanksgiving.

DaveSt
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Re: Tiger Mountain (WA) master antenna catches on fire

Post by DaveSt » Fri Nov 23, 2018 12:09 pm

sallen wrote:
Fri Nov 23, 2018 9:38 am
...Another question is why was there no pressure monitor on each transmission line along with a run monitor on the pressurization system. If I lost pressure on a large transmission line I would shut down the transmitter.
It must be top of the list of replacement items...
sallen wrote:
Fri Nov 23, 2018 9:38 am
Looks like between ATC and ERI they have some humble pie for Thanksgiving.
Yes.

Kelly
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Re: Tiger Mountain (WA) master antenna catches on fire

Post by Kelly » Fri Dec 14, 2018 12:57 pm

sallen wrote:
Fri Nov 23, 2018 9:38 am
This was a dual feed antenna, a top and bottom section so there would have to been two VSWR detectors for each transmission line going up the tower to the antenna. Another question is why was there no pressure monitor on each transmission line along with a run monitor on the pressurization system. If I lost pressure on a large transmission line I would shut down the transmitter.
ERI installed an elaborate microprocessor-controlled monitoring system that didn't work. As I understand it, there was a line pressure monitoring system that sent an alarm when the one bay burned through and fell off the tower. I believe that was the first indication of something going wrong about 6:45AM that morning.
sallen wrote:
Fri Nov 23, 2018 9:38 am
A better master antenna monitor system that not only looks at VSWR but line pressure, along with fire proof radomes, could have limited damage. Even if you can't get to the site for two hours, the immediate feed back from a good monitor system on the master antenna can still provide enough information to start to address the issue like turn off all the transmitters and go to the backup site. ERI pretty much admits this in the article.
Most broadcasters are hesitant to have multiple reasons that a monitoring system would kick them off the air, if anything because of the risk of nuisance trips. Say the line blew out of a coupling to the dehydrator, would you really want everyone to shut down? If it were me, I'd consider sudden loss of pressure to be a critical alarm condition, not something that would trip all the stations interlocks.
Skype:kellyalford Twitter: @KellyAlford

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