Ready for the winter: Winterise your antenna system!
The cold season is upon us, and while most people are preparing their homes for winter, you as a radio amateur should not forget to winterise your antenna system either. Amateur radio is not only a popular hobby, but also an important method of communication that can be invaluable, especially in emergencies. In this blog post, you'll learn why it's so crucial to winterise your antenna system and what steps you can take to ensure you can stay on air during the coldest months of the year.
UV resistance of black jacketed coaxial cables and their challenges in outdoor use
Black jacketed coaxial cables are UV resistant. But this only means that they resist the sun's UV radiation longer than other materials. Because there is no 100% protection here either.
The outer sheath of most coaxial cables offered today is made of PVC, which in itself has good UV resistance. Adding black dyes (carbon black) improves this resistance even more. Nevertheless, the cables suffer outdoors from acids, such as those found in the exhaust air of chimneys, among other things. In addition, there is the constant movement around the rotor and UV radiation. Despite all protective measures, coaxial cables can develop cracks after many years of outdoor use, through which water can penetrate and permanently damage the cable with the next frost at the latest. But even without frost damage, water in the cable can severely alter the electrical properties such as the impedance. In the worst case, corrosion occurs on the connector, for example at the transition points from the copper conductor to the nickel-plated connector housing or to the gold-plated inner conductor. The result is RF shock points, which can lead to a poor standing wave ratio (SWR) and high reflections.
Cable "breathing": a lesser-known effect and its impact on moisture in the cable
Another little-known effect is the ""breathing"" of a cable. One part of the cable is indoors, covered, and is essentially always at the same temperature. The other part lies outside and is exposed to the weather. In summer, a cable can experience temperature differences of 20 degrees and more. This strong difference in temperature leads to a pressure difference in the cable, which in turn leads to the fact that humid outside air can penetrate the cable. The water condenses when the cable cools down again. It is not without reason that many coaxial cables in professional installations are filled with nitrogen and operated at a slight overpressure. This prevents the condensation of humidity.
Therefore, after 10 years at the latest, you should take a look at your mast and check the cables. This includes the control cables, but especially the coaxial cables. Here, the cable should be inspected over its entire length for cracks, pores or even rodent traces. Transition points, such as those found on lightning protection systems or at the plug, are particularly susceptible to damage, as it is the part of the cable that moves when the rotor is turned. And while you're at it, you should also check the cable ties. They don't last forever either, poor UV resistance quickly becomes noticeable here. And then suddenly the whole cable with its weight is only hanging on the connector...
If a coaxial cable is damaged, you should replace it completely. Yes, that sounds like a good argument for more sales. But practice shows that ""patching"" RF cables is usually disadvantageous. New joints are created and the cable has more losses. This can be accepted in individual cases, but when the requirements are high, every dB counts.
Tips for the selection and care of coaxial cables and connectors
Most of the coaxial cables offered by WiMo with a black outer jacket are UV-stabilised. When selecting, pay attention to attenuation; a VHF omnidirectional transmitter for relay operation may not need the thickest cable, but a UHF system for DX operation does. Cables that are to be routed movably around a rotor should have a flexible inner conductor (stranded wire). Or - if it has to be a cable with a fixed inner conductor for reasons of attenuation - be routed in a very large arc around the rotor.
All plugs should be dismantled during the test and also inspected internally for corrosion. When reassembling, each plug should then be protected with at least heat shrink tubing, or even better with self-welding tape or sealed with rubber liquid such as Rubbaseal.
The importance of regular inspections and maintenance
Finally, it should be stressed that regular inspections and, if necessary, replacement of damaged cables and connectors are crucial to ensure trouble-free radio communication. When selecting and maintaining your coaxial cables, always pay attention to the specific requirements of your installation and protect the connectors from corrosion and moisture to maintain the performance of your radio system.