Telescopic aluminum question
 

On 04 Aug 2008 00:11:56 GMT, Ed
wrote:



My thanks to those who have responded so far. Much food for thought.
Roy, I downloaded the demo program.... BUT.... I'm going to have to
spend some time learning its operation... it appears to have a
considerable learning curve, which I'm sure will be well worth the
time.... when I get it.


Commets on salt water corrosion have been noted. I'm about 1/4 mile
from the nearest salt water.... and down wind. My mobile RV vertical
antenna has been parked here for about 3 months now and is already
showing early signs of the corrosion.

My thoughts at the moment are I can either easily remove the aluminum
elements and clean them every 6 months or so, OR perhaps I should use
an insulated wire supported by a fibre glass support. I note someone
mentioned the DX-IS poles out of Georgia. Although I swore I would stick
to only the vertical I originally spoke of, the idea of a quality
fibreglass mast does seem to have benefits for my location. If anyone
else can recommend other sources, or their opinions of robust fibreglass
masts, I'm receptive. Given the comments on projected poorer
performance of a 30 foot vertical, I suppose I need consider one that is
higher, but I have CC&R's, and while not enforced, I do not wish to
draw attention to myself.

Thanks to all, so far.

Ed K7AAT


My EZNEC models don't show much difference in radiator materials with
a diameter of of 1.5 inches. Why not steel TV masting?

It has been mentioned that 70 feet would be better but so would 140
feet! We all have some sort of limitations. The important thing is to
get a workable antenna up.

If a thirty foot radiator is what you can do that is it. Life is
simpler with a good antenna tuner (I love my SGC-237) and I am on the
air. I expect it would work well with a thirty foot wire as well.

The more important consideration is the ground issue. I bought 2000
feet of insulated wire on EBAY and it worked out to about 35 radials
of up to 70 feet. They are stapled into the grass and hard to locate
after a couple of years even though they are bright green.

I rarely use the vertical for anything other than 40-80 & 160 but it
will load up to 10 meters for sure and probably the advertised 6
meters for the tuner.

You might find my primitive experiment interesting.....
http://dixienc.us/28FtVert/28FtVertical.htm

John Ferrell W8CCW

Telescopic aluminum question
 

Ed wrote:
I am considering putting up a ground mounted vertical antenna, based
on using telescopic aluminum tubing such as is available from Texas
Towers or DX Engineering. Tubing available ranges from .500 inch to
2.125" with corresponding increase in price as diameters increase.

My vertical should be limited to a maximum of 30 feet, but preferrably
around 23 - 25 feet. I will feed it with an SGC coupler at the base and
operate 80M - 10M.

My question: Using the 6' long aluminum pieces, what is the minimum
diameter sizes I should start with to enable the antenna stand up to a
75mph wind UN-GUYED. Also, how much "overlap" should I use in the
telescoping pieces?


How much flex do you want to allow? You can make it pretty small, if you
don't mind it bending a LOT in the wind.

Are you constrained to aluminum? i.e. what about a 15-20 foot length of
chainlink fence top rail ( aka galvanized pipe) with a standard mobile
whip on top. If you're worried about conductivity, run some copper wire
or a stripe of copper tape up the side.

Telescopic aluminum question
 

Ed wrote:
I am considering putting up a ground mounted vertical antenna, based
on using telescopic aluminum tubing such as is available from Texas
Towers or DX Engineering. Tubing available ranges from .500 inch to
2.125" with corresponding increase in price as diameters increase.

My vertical should be limited to a maximum of 30 feet, but preferrably
around 23 - 25 feet. I will feed it with an SGC coupler at the base and
operate 80M - 10M.

My question: Using the 6' long aluminum pieces, what is the minimum
diameter sizes I should start with to enable the antenna stand up to a
75mph wind UN-GUYED. Also, how much "overlap" should I use in the
telescoping pieces?

I will consider alternative means of building the vertical, but I
really wish it to be unguyed .

Any info or recommendations appreciated. TNX

Ed K7AAT

I use aluminum, a lot ...

Silicone, oils/grease has assisted me quite a bit ... as you already
know the weight to mass ratio makes ones favorable to this route of
antenna construction (aluminum) ...

In my meanderings about scape yards, I find titanium is becoming MUCH
more available ... it is well worth the few available dollars ... and,
of course, depending on availability, this is much more more desirable ...

It is possible to construct a MUCH more efficient antenna than can be
purchased -- in theses cases, you are simply NOT constrained by the
"costs of manufacturing."

Regards,
JS

Telescopic aluminum question
 

Ed wrote in
. 192.196:

....
robust fibreglass masts, I'm receptive. Given the comments on
projected poorer performance of a 30 foot vertical, I suppose I need
consider one that is higher, but I have CC&R's, and while not
enforced, I do not wish to draw attention to myself.

Or one that is shorter and abandon 80m. A message you should take away is
that a 6.5m unloaded vertical (~21') is about as short as will give good
efficiency on 40m... given an adequate ground system and tuner at the feed
point.

Owen

Telescopic aluminum question
 

John Ferrell wrote in
:

....
It has been mentioned that 70 feet would be better but so would 140
feet! We all have some sort of limitations.

Ah, the bigger is better myth!

Owen

Telescopic aluminum question
 

Owen Duffy wrote:

...
Ah, the bigger is better myth!

Owen

I won't even tell you the length of mine, but 70 feet! That hurts -- LOL!

Regards,
JS

Telescopic aluminum question
 

A belated response to my initial post. After reading all the responses,
and after much thought, I have decided to fore-go using a vertical at
present.

I have problems with high winds, corrosion, some noise, ability to
place an adequate grounds system, and even aesthetics, etc. so I have
decided, for the time being, anyway, to put up a rather low dipole (NVIS)
instead.

My thanks to all who took their time to give me their opinions and
ideas. Its a good learning experiece, even if I don't proceed with the
initial plan.


Ed

Telescopic aluminum question
 

On 19 Aug 2008 04:59:29 GMT, Ed
wrote:


A belated response to my initial post. After reading all the responses,
and after much thought, I have decided to fore-go using a vertical at
present.

I have problems with high winds, corrosion, some noise, ability to
place an adequate grounds system, and even aesthetics, etc. so I have
decided, for the time being, anyway, to put up a rather low dipole (NVIS)
instead.

My thanks to all who took their time to give me their opinions and
ideas. Its a good learning experiece, even if I don't proceed with the
initial plan.


Ed
It has been an interesting thread. For some reason it never occurred
to me that the tubing sold for chain link fence top rails would make
an inexpensive and durable vertical. TV masting sems to be getting
more expensive and harder to find. I will likely use it for the next
refresh cycle on my vertical.

Of your stated objections only the matter of the ground seems to be
really tough to solve for me. I bet that in time you will try both.
The NVIS and vertical will give you two different sets of contacts!

John Ferrell W8CCW