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KFI - glitch? brief drop of carrier? what happened?

P

pianoplayer88key

Hi guys.

I was listening to Leo Laporte's Tech Guy show this afternoon, and while transitioning to a newscast at 1:30pm, the signal from KFI briefly dropped out. I wonder what this could have been? The signal strength indicator on the radio in the video linked below shows 26 dBµ briefly during the dropout, otherwise is about 59-60dBµ during normal operation.

Video here: http://www.youtube.com/watch?v=rfOoq9iiVEE (And yes this post is almost a copy of the description box in the video, with maybe a few "augmentations".)

KFI is normally 50kW ND fulltime, so I'm not sure why they would have dropped out. I've heard them do it before, quite often on Saturdays, so that's why I was able to be prepared to record it. Several weeks ago I heard them drop out several times in the space of a couple minutes, one of those times being for a good 3 or 4 seconds or so.

They do have a backup transmitter and tower on the site, but it's a lower power transmitter (25kW max, but I've read it sometimes has run at only 10 or 5 kW) with a much shorter less-efficient tower. If they were using the backup system KFI would be much weaker here.

I don't think they were switching to/from their backup rig, though, as the signal strength before and after the carrier dropping out was about the same. Any idea what could have happened?
 
Yes, I heard that A Flock of Seagulls was in the La Mirada / Buena Park area this afternoon and a few of them could have flown into the taller tower. BZZZZZZTTTTT!!!!
 
Wny is this important to even post?

Simple answer. It was a pre-cursor to an LA Zombie Apocolypse, of course.

Waste of time for a half second.
 
KFI has a protective cage around the transmitter -- that "cuts" electric power -- when the cage is opened -- when someone is working near the transmitters. This has been the case for many years. One Sunday evening -- while Dave Diamond was "on the air"
back in the 70's -- the power went off and then back on -- for about an hour. New staff had not been informed of the cage.
 
ercjncpr said:
isnt there an engineering techie forum on this board that is better suited to the OP's question
Click to expand...

I'm aware of one, but it's more general, I think. KFI is an L.A. station and this is an L.A. board so that's why I asked here. I've also seen at least one person (DavidEduardo) who knows a lot of the technical aspects of radio posting on this board frequently, and I was thinking even if he never ventures into this thread, there would be others. I figured that if I asked in the engineering board, there'd be less of a chance of someone knowing KFI in intimate detail like an engineer who lives in the L.A. area would.
 
pianoplayer88key said:
ercjncpr said:
isnt there an engineering techie forum on this board that is better suited to the OP's question
Click to expand...

I'm aware of one, but it's more general, I think. KFI is an L.A. station and this is an L.A. board so that's why I asked here. I've also seen at least one person (DavidEduardo) who knows a lot of the technical aspects of radio posting on this board frequently, and I was thinking even if he never ventures into this thread, there would be others. I figured that if I asked in the engineering board, there'd be less of a chance of someone knowing KFI in intimate detail like an engineer who lives in the L.A. area would.
Click to expand...

This is really a non-issue.

I can think of a half-dozen reasons why there might be a brief carrier cut on a regularly operating station...

... checking the operation of the switching between a main and auxiliary transmitter of the same power.

... static discharge or lightening hit sufficient to bridge the tower spark gap and short the RF to ground briefly.

... same as above, but long enough to trip the transmitter off the air and then reset / activate auxiliary transmitter.

... loss of power due to electric company failure (someone hit a power post, transformer failure, localized blackout, etc) while generator kicks in (often around 15 seconds).

... Transient caused transmitter to recycle (go off the air to protect itself, then go back on the air if it appears safe to do so). Power surge, computer glitch, etc.

... exercising the emergency generator by bring it up to speed, killing the carrier, switching to the generator and putting transmitter on air. This is done to test the transfer switch, check the generator comes on and to make sure the geny can take the load. They might run a half hour or more on the generator to additionally charge battery, burn off residue, etc., etc.

... someone hit a button they shouldn't have and recognized it immediately. Can happen while training someone on the remote control, etc.

... crispy critters. A snake, rat, mouse or other varmint crawled / walked / wiggled over a pair of contacts somewhere and caused a momentary short. Like aliens on the Syfy channel, the critters tend to be vaporized quite quickly.

... ghosts or zombies. S--t happens, sometimes with no explanation and with no forensic evidence left behind. Definitely not vampires, however, as those creatures are very sensitive to RF.*

Other, more dramatic issues could be switching to an auxiliary tower and transmitter to allow maintenance on the other tower on the ATU, tower lighting, painting, etc.

This sort of stuff, and lots of other things, happen all the time. The systems today are so fast in recovering we don't notice most of them.


* I know this because in over 50 years, I have never seen a vampire at a transmitter site.
 
Thanks, David.

The interesting thing was ... a few weeks ago it happened several times during Leo Laporte's and Neil Saavedra's shows one Saturday, mostly during newscast segments. One time it happened like 4 or 5 times within the space of two minutes, at least one of those times lasting a good 3 or 4 seconds. Also yesterday it had happened previously before I started recording the video from which I extracted the clip I posted.

I'm thinking one isolated carrier drop is one thing, but several almost in a row? (Unfortunately I don't have a video of that session.)
 
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