A story about skirted AM towers and Cellular carriers.
We take care of a few sites that have skirted AM towers with Cellular equipment installed. For the first few years, all was well. The cell carriers put up their equipment under supervision and we made sure that the AM station’s antenna still was working when the were finished. At some point, things changed.
It is a little bit hard to see because the camera is focused on the foreground and not the background, but the stiff arm from the cell carrier sector is shorting the skirt wire to the tower.
More often then not these days, tower crews show up unannounced and start working on the tower. I had a call from a client their station being off the air only to arrive on site and find a crew on the tower with the AM skirt grounded by a set of battery jumper cables. The ground crew said they kept getting shocked by the wire so they grounded it.
In other cases, they show up, do the work and leave before anybody notices. Then, at some point somebody checks the AM transmitter readings and sees a problem.
In another situation, the tower crew came and installed new equipment. They installed an insulating sleeve around the skirt wire (while the transmitter was on) but did not secure it well enough. The eventually, sleeve slipped down the wire and it shorted. No one, not even the tower owner, knew about the tower crew being on the tower.
Same tower, the sleeve on this wire rotated around so that the opening was facing the stiff arm causing a large charred, melted plastic area.
These were repaired with some left over coax-seal and electrical tape. After this, I was able to retune the ATU using my network analyzer.
The only solution, it seems, is to put up more cameras with motion detection notification so when somebody shows up unannounced the station will at least know about it.
So, how much capacitance in a piece of NMFC lying between ground and you feed line? 😀
Just seems janky to me. They should have used a ceramic standoff. I’m guessing it will eventually break down at that point and short again, but maybe that won’t matter in a few years.
I hate leased towers, and the tower companies that don’t train their crews about AM.
A few weeks ago I had a call from a tower crew supervisor the day before his visit. He was working on a cell tower almost a mile from an AM site I care for, asking for a power reduction so the detuning skirt would bite them less. I can deal with that…
Only got shocked? Were they wearing gloves? Did they speak English?
Hope you got their business card so you can send them a bill.
Tower sites are notoriously insecure. Chain link fences can keep honest people out. But crooks can easily cut thru them.
Did you hear about the KRMG copper theft electrocution? KRMG (740) Tulsa is a Cox station. And before that KAAY (1090) had their ground system stolen. The story I heard, nobody had been out to the tower site for months!
That is absolutely insane. I believe that the tower crew should compensate the station for whatever it had to pay you to repair the damage, plus any lost commercial revenue. Not your problem, obviously – but I would think that the station owner might want to contact its attorney.
I agree that installing cameras would be a great idea. Cameras could identify the culprit and create a record of activity that causes damage.
Two things come immediately to mind:
First: how on earth can you have a skirt work properly when there’s a goddamn cell sector IN THE SKIRTED AREA? Even with insulators (which always are either installed sloppily and fail very quickly, or installed correctly and fail a little later) wouldn’t that completely mess up the field?
Second: aren’t tower leases supposed to have the skirted area be exclusive to the AM station’s use? Who gets a lease that allows everyone else to put their stuff in your space? That seems insane and quite possibly against the lease, in which case you can get another tower crew to come out, rip all that new shit off the tower, and tell ’em to go bill the tower owner.
And yes, tower crews are amazingly bad about just showing up and doing work without telling anyone. Part of this is a bad feedback loop with major tower owners demanding anyone within farting distance of the tower must check in with the NOC…and then make “checking in” a 20 minute ordeal of a phone call. The worse the crews are about not calling in, the more strict the tower owners are. But yes, both the tower owner and you should have cameras everywhere around a tower so you can see when a crew is there. And when you get an alert that someone is on-site, you need to call the NOC and demand to know why you weren’t given a heads-up that a crew was climbing today. (with the point being, of course, that the NOC didn’t know either)