Re: Matching resonant antennas

Posted by Elecraft mailing list on Jul 16, 2020; 10:51pm
URL: http://elecraft.85.s1.nabble.com/Matching-resonant-antennas-tp7663149p7663245.html

 On 15/07/2020 20:30, Ken WA8JXM wrote:

> Conversely, a non-resonant antenna can have a 1:1 SWR.

On Thursday, July 16, 2020, 03:33:12 AM EDT, David Woolley <[hidden email]> wrote:

> You can only have a 1:1 SWR at a single impedance. If the design
> impedance is purely resistive, that means you can only have 1:1 for a
> resistive and therefore on-resonance load (or one that can be treated as
> having no reactive behaviour at the frequencies of interest - e.g. an
> ideal dummy load).

I agree completely, but there's a "catch".

Traveling-wave antennas, such as Rhombics, or Beverages, or leaky transmission lines, are, technically, non-resonant. However, they can each present a 50 ohm feedpoint impedance that is purely resistive, and produce a 1:1 VSWR as a result. ;-)

So, whether an antenna is resonant or non-resonant isn't the issue. The issue is whether or not a load impedance contains a reactive component. If it DOES, then it can never produce a 1:1 VSWR.

 
73 de John, KD2BD
 
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