Bonded or insulated directors?

[AlmostHandy]

On a yagi, what is the difference between director/reflector elements that are bonded directly to a metal boom, as opposed to being insulated from the boom in some way?

Does it matter?

 

[zz0468]

If an antenna has been designed with an insulated boom, then you need to use an insulated boom to duplicate it. Same with a metal boom. The spacing and element lengths can be impacted by the materials used.

 

[AlmostHandy]

Ok far out.

So, in the calculator I'm using, it lets you specify the way the directors and reflectors are mounted.

My options are:
bonded through metal boom
insulated through metal boom
non metal boom (or standoffs)

next to that, it lets you specify the folded dipole mounting.

My options there are:
Same as Directors/Reflector
Fully Insulated.

This leads me to believe that I can mount all of the elements (directors/driver/reflectors) to the boom without insulating. Is that correct? In another thread, someone told me that you must always insulate the driven element from the boom.

 

[Don_Burke]

Ok far out.

So, in the calculator I'm using, it lets you specify the way the directors and reflectors are mounted.

My options are:
bonded through metal boom
insulated through metal boom
non metal boom (or standoffs)

next to that, it lets you specify the folded dipole mounting.

My options there are:
Same as Directors/Reflector
Fully Insulated.

This leads me to believe that I can mount all of the elements (directors/driver/reflectors) to the boom without insulating. Is that correct? In another thread, someone told me that you must always insulate the driven element from the boom.

In the calculator, try changing the boom characteristics without changing anything else.

For example, gamma matched driven elements do not need to be insulated.

 

[zz0468]

This leads me to believe that I can mount all of the elements (directors/driver/reflectors) to the boom without insulating. Is that correct?

Yes, provided that the spacing and element length is designed for that. If you take a design who's element lengths and spacing are meant for an insulated boom, and build it on a metal boom, it will be less than optimal.

In another thread, someone told me that you must always insulate the driven element from the boom.

Saying "always" would be wrong. It depends upon the design of the driven element.

 

[Hoofy]

I built a 5 element 2 meter beam out of aluminum tubing for the mast and aluminum rod for the elements with a gamma match on the driven element and it works great. It is claimed to have about 9db of gain. I don't know about that but it works great.

I'm pretty computer illiterate or I would try to up load a photo.

I made some modifications in the plans and I can take the whole thing apart and put four of the elements inside the boom for transporting and bungie cord the driven element to the outside of the boom.

I also made a four element quad with pvc pipe and copper wire that you can fold flat for transporting.

It has about the same claimed gain as the yagi but has a narrower beam width.