I am building a 440 yagi. Thinking of using sch 40 for the boom. Will
it warp in the hot sun of summer or over the years being outside in the
weather?

Don't know about warp - but it will deteriorate.
If you have to use plastic, I'd go ABS.

There is sunlight resistant or uv resistant electrical pvc, but the short
answer regarding electrical pvc is yes it will warp. You'd probably stand a
better chance with sch 80
wrote in message
ups.com...
I am building a 440 yagi. Thinking of using sch 40 for the boom. Will
it warp in the hot sun of summer or over the years being outside in the
weather?

I think the grey PVC electrical conduit is more sunlight resistant, but
I don't know about its insulation properties at UHF.

Perce


On 01/18/05 04:54 pm tossed the following
ingredients into the ever-growing pot of cybersoup:

I am building a 440 yagi. Thinking of using sch 40 for the boom. Will
it warp in the hot sun of summer or over the years being outside in the
weather?

Cant say for sure...but, i made a PVC umbrella stand out of 1" and use
it every summer in direct sunlight ; has not bowed at all.

whether it will or not is up for debate. whether or not its wise is not.

use something else.

randy

wrote in message
ups.com...
I am building a 440 yagi. Thinking of using sch 40 for the boom. Will
it warp in the hot sun of summer or over the years being outside in the
weather?

wrote in message
ups.com...
I am building a 440 yagi. Thinking of using sch 40 for the boom. Will
it warp in the hot sun of summer or over the years being outside in the
weather?


W7CJK here. I've used sked 40 and lighter for a number of experimental
antennas. Very convenient and cheap. It probably will be OK as to warp if
it does not cantilever (project from a support) more than three feet. I
built a double rhombic for 900 MHz with a twelve foot boom and used diagonal
wire struts back to the mast to support the ends which were six feet out. It
was up several years without incident before the experiment was terminated.
Don't remember now but it may have been 1" sked 40. Most of my experiments
used 3/4" stuff.

IMHO it's a good material for experimental use as most ham projects are. If
you plan a rather permanent installation, metal gives more reliability.

I would love to use conduit but it is conductive and I cant figure out
how to insulate the elements from it. I was thinking of running the
elements straight through the pvc. ANy ideas?

wrote in message
ups.com...
I would love to use conduit but it is conductive and I cant figure out
how to insulate the elements from it. I was thinking of running the
elements straight through the pvc. ANy ideas?

The directors and reflectors do not need to be insulated from the boom.
However, the exact length you need will vary depending on which way you go.
The center of the driven element may or may not need to be insulated,
depending on the type of feedpoint matching. I generally used gamma match
so the center of the driven element did not need to be insulated. On the
driven element, slight variations in design length can normally be corrected
in the matching process.

If you're fairly new to this stuff and following someone else's design, I
would follow the mechanical details as closely as possible. Minor changes
can alter the resonant frequency of the directors and reflectors enough to
seriously impair the directivity and gain.

SJF wrote:
wrote in message
ups.com...
I would love to use conduit but it is conductive and I cant figure
out
how to insulate the elements from it. I was thinking of running the
elements straight through the pvc. ANy ideas?

The directors and reflectors do not need to be insulated from the
boom.
However, the exact length you need will vary depending on which way
you go.
The center of the driven element may or may not need to be insulated,
depending on the type of feedpoint matching. I generally used gamma
match
so the center of the driven element did not need to be insulated. On
the
driven element, slight variations in design length can normally be
corrected
in the matching process.

If you're fairly new to this stuff and following someone else's
design, I
would follow the mechanical details as closely as possible. Minor
changes
can alter the resonant frequency of the directors and reflectors
enough to
seriously impair the directivity and gain.
I am new to this. SO you have a plan that uses a conductive boom?

wrote in message
oups.com...

I am new to this. SO you have a plan that uses a conductive boom?

Sorry, I don't. Suggest you check the ARRL handbooks (library?). Any
departure from a specific design of a yagi generally requires considerable
skill and some test equipment. Good luck.