Foundations of Amateur Radio Antennas out of sight and out of mind ... Previously I've spoken about the dynamic nature of your station. Even if from day to day use, nothing changes, things around you are always in flux. Propagation changes, power fluctuates and the environment in which your antenna operates is dynamic. Mobile stations even more so. A few days ago we had a gale come through, strong enough to do some major damage, rip off some roofs, break some trees, cause flooding, cause power outages, plummeting temperatures, the first of the Winter Storms. Obviously, checking out your antenna after such an event is expected. Better still, stowing your gear before the event is even better. Such extreme weather events are an obvious trigger to attending to antenna health and well being, not to mention, maintenance and repair. The thing is, it's not the only time you should check out your antenna. Every day it's subject to change. The sun rises in the East, follows its path along the sky and eventually sets in the West. The temperature and humidity change throughout the day and continue to change through the night and the next day it starts all over again. Peppered with sun, rain, snow, salt, corrosion, expansion and contraction, your faithful antenna sits there ready for you to get on air and make noise, until one day it isn't. You could just wait until it falls down, dies, perhaps becomes a hazard to anyone within gravity range, not to mention, destroy your radio when you key it up. Or you could check your antenna regularly and look after it. Inspect and test it regularly, run you analyser across it every couple of months, you know the drill. Most antennas are out of sight for most of their life, but they should never be out of mind. During the weekly F-troop net we started discussing this - as well as an in depth conversation about launching wire into trees - and there were several suggestions worth investigating. One amateur pointed out that the level of complexity in the air dictates the amount of maintenance. A log periodic antenna on a rotator needs more Tender Loving Care than a wire hanging off a tree. Another suggested that you should regularly check the tower supports - technically the mast supports - a tower is self-standing and a mast is not - the best way to remember is that is the Eiffel Tower doesn't have any guy wires. Before a storm, if you have warning, you should check the supports, wind down anything that goes up and down and you should think about how you're going to earth the coax. I've previously covered the weirdness that lightning and charge represents, even at distance, so don't wait until it's overhead. There were suggestions of using spark plugs and Mason Jars, but I've got no supporting evidence either way. My geek background is sceptical, but I'm open to learning more. I've seen installations where a coax switch is used where the antenna is switched to a shorted socket, so the inner and outer braid of the coax are connected to each other. One amateur suggested that an antenna tuner is cheaper than a radio, and that if you leave it in place during a storm, blowing that up is cheaper than blowing up a radio, but your mileage may vary. Also, if you have spare cash to burn, I'm happy to take your donation and relieve you of that fire hazard. It's interesting in and of itself that antenna maintenance is often discussed in terms of extremes, lighting, storm, wind, ice, etc. and less so in terms of regular maintenance. Finally, if you're only using a temporary antenna, you're not exempt from this. You're actually likely to have more failure, since the act of erecting and lowering of the antenna is likely to cause more wear and tear. The antenna is the final part of the transmission chain and it should be treated with the same respect as the power supply at the other end. I'm Onno VK6FLAB TL;DR This is the transcript of the weekly 'Foundations of Amateur Radio' podcast - for other episodes, see http://vk6flab.com/
I only realised one huge bonus from my doublet after erecting it. This was the potential for it to last, maintenance free, until long after I've gone to meet my maker. It's made from two continuous lengths of insulated stretch resistant steel reinforced antenna wire, one wire forming the left hand top section and left leg of the ladder line, and the other forming the right hand top section plus right leg of the feeder. This antenna thus has no joins anywhere outside the shack, tunes up on every band from 6m to 80m, and while no match for a beam, the benefits listed above make a great choice for anyone wanting a trouble free installation that will always be there ready for use.
An OCF 160m dipole, with a pulley and weight to withstand wind and swaying of the supporting pine trees, gives fine results too. Big wire seems to be particularly good with low solar activity. It tunes 160-6m . The copper is weathered black, so it almost disappears. The XYL is relieved that I have cooled on erecting high towers and enormous multi-element beams. (For now!) I envy maintenance-free installations; mine seems contingent on continuous patrolling and tree-pruning... I'm tempted to do another dipole specific for 6m, for comparison.
