RadioBanter - View Single Post

December 21st 04, 08:39 PM

On 21 Dec 2004 11:16:16 -0800, wrote:

No, the tv tower is already up. I meant I can weld the elements. (Of
course only if it is weldable material.) I was wondering if emt tubing
would be a good choice?

Hi OM,

The consensus is that it is not. If you are going to invest your time
and effort, short-cuts generally lead to repetition. You wanted to do
this once? You are in the wrong hobby. Better is how to plan doing
it many times, but planning to do it in the least stressful way.

The antenna would be about 25 feet up.

You had a range requirement of upwards to 70 miles. With a 25 foot
elevation, your mileage range is roughly the square root of twice that
- or 7 miles. You can double that if the other antenna is up equally
far. If you are on a rise of land above the mean level, add that to
your elevation. If the antenna at the other end is much higher,
compute its range (hopefully a mountain top).

I had someone else tell me that
a j pole does not work very well. Is this true?

Varies by user as it is susceptible to transmission line length
problems. These problems are SWR related. However, that aside, as a
principle antenna for the range you ask, then that antenna at the
other end has to make up for a lot (it better be higher, an array, or
some combination).

I can rotate the mast by turning the antenna rotor hooked to my tv down
stairs. The only pain would be running down stairs every time I want to
do it.

You have to now investigate if your tower/rotator can in fact stand
the additional wind load factor (or weight, or moment).

What would you do in this situation? Can you get as good as or better
performance building one yourself?

Depends on your resources. It already sounds like you are shy there
in finding aluminum of the proper grade. Best advice is to visit a
metal scrap yard in the crummy part of town. Or - bite the bullet and
pull out your wallet.

If all this is to hit a repeater, and a popular one, you should simply
try it and see what happens with a rubber duck. Then build a simple
ground plane ($5) and hoist it as high as you can (on a broomstick out
the 2nd floor window will do as a test). Popular repeaters are
popular because they solved all these problems for you (by being high
and having gain).

73's
Richard Clark, KB7QHC