tony sayer wrote:
In article
.com, scribeth thus
Lets be silly. Take a commercial yagi TV aerial, take a strip of
cardboard, and make a full size copy of the layout using bits of 2.5mm
T&E cable for the elements, and the cardboard to replace the spine.

How well would it work?


NT

It would work .. so would any bit of metal, question is by how much
relative to what;!..

Tony's right: the good news about yagis is that they "want to work".
Anything that is sufficiently yagi-like will tend to be directional and
have some forward gain, at some frequency or another.

Making them work *well*, and on the frequency that you want to use, is
quite another story.

The active elements don't have to be "connected" together.
The diameter
of the 2.5. Elements would have an effect on the bandwidth..

By removing the metal boom and element clamps, and also changing the
diameters of the elements, you have changed two things that affect the
resonant frequency of each element. This shifts the frequency response
of the whole array. And as for the changes in the driven element, and
how they might affect the transfer of signal into the downlead... you
have no way to know.

If you are aiming to copy an existing Yagi design, you must copy:
* all the element lengths
* all the element diameters
* the element mounting method.
That means: copy EXACTLY. If you change any of these details, you are
actually building a new design. The following page isn't specifically
about TV yagis, but it gives some idea of what's involved:
http://www.ifwtech.co.uk/g3sek/diy-yagi

Sorry, but this really isn't a subject that you can just wander into and
immediately succeed. Unless you have such a strong TV signal that none
of this matters, you'd be better off with a commercial yagi.



--
Ian White