Visit to a radio station

[Iain McFadyen]

Yesterday morning (first day of Carnival here) there was a motor vehicle
accident resulting in a car completely breaking a sturdy concrete
electricity pole in half. The car then proceeded a few extra metres, and
collided with a large concrete foundation.

The car ended up in two pieces: The whole engine separated from the body of
the car, and the two parts came to rest about 30metres apart.

Puzzled by the subject of the message yet? Keep reading...

The concrete pole belonging to the electric company supports one of 'my'
fibre optic cables running from Port of Spain to Chaguanas. So I was called
and made aware of the situation.

The emergency services and wrecker had left the scene before I got there
(but I have pics from a colleague)

Arriving on the scene. the first thing I noticed was that the concrete
foundation a few metres from the broken pole had an anchor shaft with a
characteristic fantail piece of flat metal, with holes along the upper edge.

http://www.astrosurf.com/luxorion/Radio/guy-wire-rohn-n3rr.jpg

 Strewn around the foundation was a length of chain, three turnbuckles,
and... a guywire... for a mast!

Just a few metres from the accident was the transmitter shack of "730am,
Radio Trinidad". One of the masts, now missing one complete set of guys,
was leaning at 10-15 degrees. The separated guy wires were lying against
the fence of the radio station, clear of the crash site, and so nobody
noticed them particularly as when viewed from the crash site itself, the
tower was leaning away, and still looked vertical!. I hastily grabbed some
offcuts of fibre optic cable from the car, and tied off lengths to the ends
of the guy wires, pulled them back to the anchor, and made it safe. Fibre
optic cable has a strength member through the centre. Enough to put tension
on the cable. I used 3-4 lengths overlaid and interwoven.

I then spent a full half hour at least, searching the web and calling '411'
to try to track down a phone number for the owners of the radio station. No
luck. Found a few web pages, but no way of getting hold of them directly.
(I could submit a request for a 'shout out' or a song request, but no live
way of directly contacting them!)

I called a couple of Radio Ham friends,... one who knows most of the
Commercial Mobile Radio companies, and another who is a rigger for the
Police Force. They scurried off to check their Rolodexes.

Meanwhile, I went back to put a little bit more tension on the temporary
guy fixes. Managed to get the mast back to maybe 5 degrees from vertical. I
wasn 't worried about an immediate issue: The wind was calm and the weather
was clear with no forecast of storms. But if the wind had picked up, I
think the mast could have blown over quite easily, given the weight of the
other guys pulling it over and the slim cross-section of the lattice, and
the amount of sway I experienced before even starting the emergency work..

So I am ready to leave: The utility pole has been replaced, the fibre
re-attached and coiled properly, and a temporary fix in place for the guys
of the radio station, when a car pulls up, and a person walks up to the
radio station entrance and goes inside. I ran after him and told him the
story.

"That probably explains why my telemetry link is down" he said. Turns out
that they have a 5GHz internet link using a small parabolic antenna on the
affected mast, and with the mast leaning, it was out of alignment. So I
explained the underlying issue, and he called out the station Engineer and
a rigging team.

So, now for the good stuff: I got a tour of the station!.

The station consists of Rockwell 820F, 10kW AM transmitters, on 730kHz. Not
sure if '820F' fully describes what was there:

Working modulator rack
Working RF rack
Exciter rack
Changeover switch/dummy load rack
Standby modulator rack
Standby RF rack

Six racks in all. The only online reference I can find refers to an 820F
being three racks:
http://www.oldradio.com/archives/hardware/Collins/820.htm

In addition to that, there was a further suite of three racks, making up
the 'standard' 820F. Stripped of tubes and some power supply parts.

The modulator consists of a pair of 4CX5000.
The RF unit consists of a pair of 4CX5000 also.
The RF drivers are 6146B.

What a fun day for me, but not for the driver of the car.

Iain
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