# Antenna Q vs pattern shape

Is there any reason to think that changing the Q of an antenna would affect the directional pattern, assuming that is the only variable that changes?

Restricting to values of Q say less than 1000.

Assume this is an HF loop antenna which could reach Q values of <1000 somehow, and assume it is made of magic metal so that I can vary the conductivity and therefore the Q as desired without changing anything mechanically. The capacitor is of course perfect.

So as I increase resistance of the metal, does the pattern change?

I miss having access to XFDTD, I could have just simmed it.

• How will you change the Q and not the current distribution? Oct 18 '17 at 21:38
• Varying resistance. Assume that I can. Oct 18 '17 at 21:40
• Well if the resistance is somewhere that has no effect on the pattern, like across the feedpoint, then it will have no effect on the pattern. If it's in series with the middle of the radiator, it will affect both the Q and the pattern. That said, the pattern of a short dipole and an ideal dipole are so similar that the pattern won't change much. Oct 18 '17 at 21:45
• Just for argument, say it was something like using lead pipe (or worse) for the radiating elements. No lumped resistor. I understand it's a horrible idea, but I'm trying to find documentation for or against the idea that a change in Q without any other change like resonant freq or mechanical arrangement would distort the pattern. Oct 18 '17 at 21:59
• @user103218 could you update your question with more information, what type of design you are looking at? what materials? what frequencies? how do you plan to change/restrict Q? for what purpose? what is it what you are trying to accomplish? and any other information which could help us understand your particular situation and question. Oct 19 '17 at 8:44

Changes that affect the Q may change the gain of the antenna without any changes to its pattern. In antenna engineering, the pattern of the antenna is called Directivity. It is the Efficiency of the antenna times its Directivity that yields its Gain: $$Gain=Efficiency \times Directivity$$