Re: NEC-LIST: Difference between F/B and F/R ratio?

At 09:13 AM 11/22/2007, electronicbattle wrote:
>Hello
>
>I know that front-to-back ratio expresses the difference between the
>mainlobe on boresight and the rear lobe response at 180 degrees to
>that, but what is front-to-rear ratio?
>
>I've seen F/R ratio mentioned a couple of times on a few websites,
>and indeed 4NEC2 displays F/R as well as gain and F/B results from
>simulations. However, I can't find anything in the literature. Is it
>something that is peculair to HF antennas, by chance? Can anyone
>explain what it is please?

Essentially it's the ratio between mainlobe gain and the integrated
side/back lobes. I don't know how 4nec2 calculates it, but one
convention is to use "rear" as anything more than 90 degrees from the
main lobe.

Another measure is main to peak sidelobe

Another question is whether it covers responses at other elevation
angles. That is, the az and elevation of the peak response is easy
to figure out and non-ambiguous, but when comparing front/back or
front/rear, do you look at ALL elevation angles in the "non-mainlobe"
direction or just the one that matches the elevation angle of the
mainlobe peak response.

Jim Lux

>I apologise if this is a little off-topic seeing as it isn't
>expressly NEC-related, but it does get encompassed c/o Arie Voor's
>excellent 4NEC2 (actually, 4NEC2 displays F/R as a ratio of the
>mainlobe and the orthogonal lobe which may be an error).
>
>Thanks for any comments.

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