Out Of Tune! July 12th, 2013
Internal ATUs are becoming more and more popular, and we are getting to the point where most HF radios now have them fitted as standard. This is good news, but with this trend comes problems for many owners. They find that in a lot of case they are unable to match their antennas. So why should this be?
The truth is that most of the ATUs fitted inside radios have a veery limited capability and are really only able to handle relatively low VSWRs. If you have a dipole or beam and the VSWR rises at the edges, then the chance is that the internal tuner will do its job. But when it comes to the popular G5RV,it is a completely different matter and you may well find that it will not work on some of the bands. There is nothing wrong with your antenna or the tuner, it is just that the tuner is being asked to match something that is beyond its capabilities. And as for end fed wires, don’t even try it!
If you are going to be erecting a lot of different antennas for HF work, you will almost certainly need to invest in an external tuner, either manual or automatic. And if you go down this road the you should switch off your internal tuner. And a BTW. It is not uncommon for customers to call and say that they are not getting very good results from their set up even though they have a good SWR. Time and time again it turns out that this good VSWR is achieved not because of the antenna, bur because of the ATU. An ATU does not remove VSWR on the feeder, it only removes it on the cable between transceiver and ATU. So if you have 8:1 VSWR with the ATU switched off, you will still hav the same VSWR with it on and the same feeder losses that result. Peter G3OJV.