What is an antenna system / aerial ?

An Antenna system or aerial system, is in its entirety the following, the the plug (beit PL259, N, BNC or any other plug) the feeder, balun’s and chokes the ground plane and radials, the antenna its self.

Is my radio Deaf? 90% of the time, a radio is not deaf its the antenna system that is lossy or noisy. A noisy antenna will make the radio sound deaf. The problem usually is one of a few things, the most common being bad electrical connections, the second being artificially induced noise (Power line) and the third being bad feeder, however there are many more possibilities. How to rectify them is a little more complex. Firstly, connectors and plugs cause loss, so the first thing I would do is do away with any non essential connectors. Airspaced baluns work, however they need to be affixed properly, if they look a mess then electrically they are a mess! Use Choke baluns at both the feed point of the antenna, and the Low pass filter in the shack, if you don’t then your feeder becomes a part of the active* antenna by using a choke you isolate it. Invest in decent cabling, don’t use the cheap stuff, its often no good. for example I bought a roll a few years ago for a field day, we needed 20m (10m down the mast and 10m to the car.) The plugs where soldered and connected properly but the impedance was 100Ω so we stripped the cable, in some places there where many strands of screen, in other places none!

Ground rods, I’ve been told many times that a decent ground requires at least 6′ of spike, but who sells these, certainly the dealers don’t. I’ve always used 2″ copper pipe (at least 4′ long), the advantage of hollow pipe is that on really hot days, I can fill it with saline water and it improves the ground a little. Also you can improve your ground by keeping it moist with a hosepipe.

When building antenna’s remember this golden rule. “The diameter of wire is directly related to the bandwidth of the band your cutting for” so using 2mm diameter wire in a large band like 80m will narrow your SWR. Always cut antennas for the part of the band your going to use most, a tuner will adjust the impedance seen by the transciever and fool it to believing that its a 50Ω load. Many people will tell you that you need many radials with an antenna system. I call Bull on that one, many studies have concluded that eight to ten is the most you need (unless multiband) any more than that the benefits you get are completely outweighed by the costs and you won’t hear the difference!

Always waterproof connections, use PTFE tape and if possible liquid tape too, water ingress is costly!

Isolate your mains power, by using a choke to rid yourself of noise on the radio before the feeder, your noise floor will also drop!

error: Content is protected !!
%d bloggers like this: