Antenna repairs

antenna mast

Me, climbing the main north/south antenna to fix damage caused by high winds and heavy snow. You can see the problem – the right hand side should be a mirror-image of the left, but it’s all gone Pete Tong (that’s a technical communications term). Thanks to Phil for the photo.

I admit that this doesn’t sound like the most exciting title for a post unless you are some sort of crazy radio enthusiast. However, having spent the whole of yesterday making essential repairs to one of my antennas I was reminded me what an amazing job this was – so read on…

Mast climbing

Tooled-up and ready to go. Thanks to Phil for the photo.

Here at Rothera we still use HF radio (you might know it as shortwave) for communicating with field-parties, aeroplanes and other bases – it’s a simple but effective way to keep in touch in places with zero telecoms infrastructure, and is much cheaper than using satellites. The parties that we’re contacting by radio can often be deep in the continent, many hundreds of miles away, which means that we have to use some powerful transmitters and some pretty chunky antennas. The efficiency of the antennas is improved substantially by having them high off the ground, so they’re all mounted up masts. This is all very well until they go wrong.

One night this week we were hit with some unusual weather – a combination of high winds (over 60 knots) unseasonably high temperatures and heavy, slushy snow. This coated everything outside with a thick layer of rime ice which then solidified and stuck fast when the temperature dropped again. When I went out to inspect the antennas in the morning, most of them had suffered some sort of damage. In places, a five or six inch diameter of solid ice had stuck to the metal guy lines and steel tubing, which then simply fatigued and snapped in the gusting winds.

antenna mast

Setting off up the mast. Thanks to Phil for the photo.

The worst damage was to the main North/South fan-dipole antenna, a vast spider’s-web construction mounted between two 18 metre masts high up on the point. One of the supporting cables on this had snapped, leaving the remaining wires flapping uselessly around in the wind. When I discovered the damage, I tried to remain outwardly professional but was actually rubbing my hands in glee – I’d wanted to climb this antenna ever since I arrived at Rothera, and now was my chance.

Unfortunately, it was another couple of days before the high winds dropped below the safety margins for climbing the masts, but on Thursday morning I woke to calm conditions and a favourable forecast for the day – time to get to work. I roped in Tim, Tom and Phil to help out and between us we loaded all of the climbing and repair equipment into a skidoo trailer and headed up to the antenna.

The first job was to lower the antenna to ground level so that we could work on it in relative safety, so I donned a harness and headed up the mast, weighed down with ropes, pulleys, winches and a heavy pile of shackles. These narrow masts are pretty easy to climb, but it was a very different experience from the last time I tried it in a yard in Cambridge during the English summer. Now, with the temperature hovering around -16⁰C, it didn’t take long for my hands to become uselessly cold as they gripped the frozen metal, and the light breeze turned my breath into authentic Antarctic beard-ice. However, once at the top, it didn’t take too long to secure myself, unhook the damaged cables and attach them to a rope for the ground team to lower down.

antenna mast

Lowering the antenna on a rope. Thanks to Phil for the photo.

By lunchtime we had the whole construction down on the ground, and the fixing could begin. I was determined to finish the job and get the antenna back up within a day, so we were under pressure to work fast – anything left on the ground at this time of year gets quickly iced-in and subsequently takes hours to dig out again.

It took most of the afternoon to replace the damaged cable and make a few other minor repairs. Again, this was mostly due to the trickiness of working in the cold. Try as we might, we couldn’t coax my poor, cold gas-powered soldering-iron into life, so had to lug some of the cabling down into the workshop to solder it. Even a simple job such as screwing a small nut onto a bolt can be incredibly frustrating when wearing thick gloves. The only solution is to take them off, but then you’ve got to work fast before your hands become painfully cold, requiring you to stick your hands in warm pockets and jump around for a few minutes in agony as the hot-aches take hold. At least this time, when looking for somewhere to temporarily store a metal bolt, I didn’t make the mistake of absent-mindedly freezing it to my lips – you only make that error once!

antenna

The antenna on the ground – a bit of a spider’s web! Thanks to Phil for the photo.

The sun was starting to drop below the horizon by the time I went up the mast a second time to hoist the newly-repaired antenna up into place and secure it. Once I’d climbed back down again, we hooked up the last couple of cables and headed for some well-earned dinner. The real test came later on, when I tried using the antenna to talk to one of our winter-trip field parties, currently camping out in the middle of Adelaide Island –  happily, they came booming through on the radio, having enjoyed a beautiful day of climbing and skiing. Success!

antenna

Me and Tom reattaching the damaged cable, and grimacing due to cold fingers! By the way, that’s beard-ice and not stray bogies. Thanks to Phil for the photo.

There is often a bit of one-upmanship in Antarctica – there’s always someone out there who is eager to describe how they’ve done more extreme work in colder conditions than you. I find that this makes it difficult to describe some aspects of a job like this without sounding like I’m joining the bragging club. However, the reality for me is very simple: I still can’t believe that I’m paid to do play with large-scale Meccano sets outside, on the top of hill in the middle of Antarctica, and I want to tell everyone how much fun it is! My only problem when doing a job like this is that, despite being in my 32nd year, I still have this nagging feeling that there should be a responsible adult present…

antenna mast

All fixed, as seen from the top of one of the masts. That’s our new shiny copper cable on the left.

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2 Responses to Antenna repairs

  1. 5olly says:

    Well whatever you say, I find it fascinating.

  2. MichB says:

    I’d have no idea about the radio, but the climbing looks fun and view to the shore is pretty great so I’d judge it worth the effort 🙂

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