Building a shack: Part 3 - the ingress of coaxial cable

Foundations of Amateur Radio One of the potentially trickier aspects of putting together your shack is connecting the radio to the antenna. On the face of it, the challenge is limited to making sure that you have mating connectors on both ends, but when you actually start implementing this you'll run into several other considerations. The very first one as I said is the connector. Every amateur I've ever spoken to goes through the same process. You pick a connector, typically the one that your radio comes with, then you adapt the connector on your coaxial cable to suit, then you'll get an SWR meter, a dummy load, some testing gear, a coax switch or two, perhaps another radio, or an amplifier and along the way you'll discover that you now have a growing collection of connectors to choose from, and that's just the connectors inside the shack. After considering connectors, you'll start to contemplate the coax itself. You'll likely weigh price against signal loss, but there are other aspects to the selection of the right coax for the job. For example, how do you get the coax actually into the shack? One of the main challenges associated with solving that problem is surprisingly something that rarely affects our hobby, other than any human factors associated with the phenomenon of "weather". Getting coax into a shack generally involves passing through a weather proof barrier of some sort. In doing so, you're likely to create a place where the weather can make its way into places it's not supposed to. Water can and will travel along your coax. Hopefully on the outside of it, but if you're unlucky, on the inside too, likely destroying it along the way. At first glance you'll think that water only travels down with gravity and in an ideal world you'd be right, but as it happens, water will happily do other things like get blown by the wind, or condensate in temperature gradients, like those found near a hole you just created in your lovely weather proof barrier. If your shack has existing openings, they're generally the easiest to appropriate, things like gaps in the eves, existing vent holes, between roof tiles or sheet iron, plenty of existing places where you can get from inside to outside a shack. Note that this is also the case if your shack is a trestle table tucked away in an office, like mine. Before I continue, I'm about to raise some potential safety issues, but I'm not an occupational health and safety professional, so, do your own due diligence. If you do need to go into your roof space, height aside, consider it a dangerous place. Make sure that there's someone to check on you and consider alternatives to climbing up there. Wearing a face mask and full body clothing is a very good idea. Often you'll find exposed wires, deteriorating or toxic insulation and other nasty things, conductivity of steel roof frames and pipes are also a hazard, so be extremely reluctant to venture there. Avoidance is preferable. Working at heights 101: Don't .. that said, there may be no alternative. You can lift corrugated iron sheets by undoing the roofing screws. If you do, make absolutely sure that you don't make a string of water inlet points when you put it all back together. In lifting a sheet, you can access the roof space and run your coax. Sometimes the gap between the corrugation and the rafters is sufficient to push the coax through, but if you live in a hot climate, make sure that it doesn't touch the sheeting, since coax is likely to distort, if not outright melt, if it's in direct contact with the iron sheet while the sun is belting down on it. Consider the temperature rating of your coax. Similarly, terracotta roof tiles tend to have enough space to allow coax to enter the roof space. Be very careful, since they're often fragile and potentially irreplaceable. Look for openings like existing roof fittings, things like chimneys, vent pipes, roof ridges, etc. for simpler points of entry. If you need to make a hole in your roof and seal it, there's special rubber grommets for this purpose. You cut a little opening in the grommet, too tight for the coax, then force it through. Seal to the roof with UV-stable silicone and you're good to go. Check them every so many years, they deteriorate. Speaking of silicone, if there's an existing hole that you're using, don't just seal it up, it might be there for a reason. Windows often have vent holes or gaps that will fit some types of coax and there's inserts you can use to open a sliding window that will accommodate coax, but consider the security of that window before you commit. There's also special flat coax for running through a window frame or under a door, but check before you buy that they're suitable for the job. Ladder line is also an option, it's much thinner, can travel longer distances, but its performance can be affected by corrugated iron and other conductors. Rarely if ever does the initial acquisition of coaxial cable involve details ...