[Antennas] Re:Design questions for directional antennas

Mon Aug 1 21:31:54 EDT 2005

The information you seek is most likely in one of the old ARRL antenna
books. Look under plumber's delight antennas.
73.oow
> I've made a few homebrew directional antennas over the years. In some
> cases, I merely followed a design in a magazine article. In a few
> cases, I measured and copied a commercial antenna. While all but one of
> these antennas worked fairly well, some questions nag at me:
>> 1) Some yagis have their non-radiating elements electrically connected
> to the boom (and therefore each other). I copied a Cushcraft 900 yagi
> (with a metal boom), but made the boom on mine out of wood (using the
> same diameter and length radiators for all elements). I did not connect
> the non-radiating elements - the directors and the reflector -- to each
> other. While I did not notice any difference in performance between the
> two, I also do not have an antenna range to verify exact performance,
> alternatively relying on just operating.
>> Q1: Is there any effect on performance by either connecting/grounding
> the non-radiating elements ??
>> 2) Commercially made broadcast TV receiving antennas usually have their
> elements in a "V" shape (sort of like a horizontal inverted V).
>> Q2a: Other than possibly cosmetics (the antenna 'pointed' at the
> station) is there a design/performance reason for this ??
> Q2b" Does this "V" shape have any effect on element length or bandwidth
> ?
>> 3) A dual band yagi design like the 'Arrow' handheld has the elements
> for the 2 bands at right angles to each other.
>> Q3:Does this type of element positioning eliminate any effect one band's
> elements has on the other band ?
>> BTW: The one design that did not work well nagged me. I ended up
> following a few suggestions, and the performance eventually (and
> seemingly) closely equaled the original design. The change with the
> most impact was replacing stainless elements with aluminum (the original
> design was made with aluminum) - go figure...
>> ======
> Frank
> _._ _.