View Full Version : Resonant vs Non-Resonant Antennas (#538)

10-04-2021, 11:31 AM

10-04-2021, 04:44 PM
Resonant is always best. When wavelengths begin to get overlarge (at lower frequencies) to be physically unfeaseable. Then is when either the construction of the antenna can be adjusted to make things work with shorter elements. This involves using certain capacitance and inductance characteristic of the design to make it appear as a specific wavelength on the end of the coax. Often tuners are used at the final stage and will match both the coax and antenna together as one element. Tuners are a last resort as the remove the offending components of the transmitted signal to ground, reducing the effective transmitter power at the antenna.

The DB
10-04-2021, 11:32 PM
I love absolute statements like that, especially when they are not entirely correct...

All end fed 5/8 wavelength antennas are non-resonant antennas, yet most people on the CB band agree that they make the best base antennas, and other bands as well... Don't let that antenna tuner at the antenna's feed point fool you, the antenna itself is clearly not a resonant length. Actually, the posted video talks about this.

The secret to using antenna tuners effectively, as was stated in the video that Booty Monster posted, is the feed line between the antenna tuner and the antenna. If your stuck on coax, don't bother with antenna tuners, ever. Even LMR-400 might as well be a piece of water damaged RG-58 next to window line or the even less lossy ladder line... Losses here are the key, and must be lessened at all costs, especially on a line that has significant SWR on it. Its like this knowledge is lost or ignored these days. Several times in the past I have seen an antenna tuner into ladder line as the main feed system outperformed coax to a remote matching circuit at an antenna's feed point. This doesn't happen all the time, and depends on several factors, but it has happened, and I'm not the only person who has experienced it.

I once put together a presentation that started with the performance of the antenna itself, no feed line or matching circuit, then added the various components of a full, real life antenna system and showed the effects of said components on the overall performance of the antenna. Unfortunately it was on a drive that I lost, so I don't have it any more. Perhaps I should recreate it. A lot of people would be surprised at what has how much of an effect on the antenna system itself. The things that affect performance the most are not what most people actually expect...

The DB

10-06-2021, 10:18 PM
I've always used tuners when the matching at the antenna is not to my liking. 5/8 wave appears as a full wavelength when using the gamma element to match to the mast. Ground radials play an important part too, creating a ground effect and affecting the SWR. I use only RG-214 with the double shield, not that flexible but great characteristics. Using different matching methods, even a wire fence can be matched with a tuner but most energy is wasted and very little EMF will be emitted. My favorite is a balun in a tree top and a couple miles of wire in the wilderness, no matching required.