I just can't get my SWR Flat, what am I doing wrong?
When you install antennas you have to understand there are various factors that could impact the tuning of the antenna. I am going to run through a few of those and try to keep it simple. The following are some of the things to consider if you are having problems tuning your antenna.
Proximity to other things, like carports, trees, buildings and biological matter like animals and humans.
Resonance of antenna, the SWR, is it the correct length, is there a solid ground connection etc.?
Last but not least the feed point impedance match, where the coax cable hooks onto the antenna itself.
What a lot of folks don't consider is during a mobile installation what type of ground are you on? This can also have an effect on the tuning of your antenna, by ground I mean Dirt, Asphalt, Concrete etc..
Considering the previous factors lets say you have tuned your antenna to its lowest swr possible but you are still looking at a 1.5.1 swr (really not bad for most applications) and you meet all the other parameters. I would suggest looking at the feed point impedance, you will need an analyzer to do this and it will give you a general idea of what you have to do to get your SWR where you would like it.
Different antenna designs require different matching at the feed point, for example the cubical quad antenna, most loops will need a 4:1 transformation balun to function effectively taking the 200 ohm impedance from the loop to 50 ohms on the coax and transmitter making it more efficient.
A simple solution for most applications on CB is a hairpin match (my favorite), Gamma match, or introduce a shunt coil into the equation.
Tuning antennas can be a real pain in the ass but doing it correctly will make all the difference in the world, an amplifier cant make a poorly tuned antenna work better.
What kind of Conditions are my Conditions in?