[TowerTalk] CATV Hardline As Elements

[Mike]

Hello Bert,

Couple ideas for you - both have been successfully used in the 
past:  bamboo or central vacuum cleaner pipe for quad spreaders.

Find someone with a bamboo patch and you will find someone who will welcome 
your cutting some out.  Stuff is a menace as my neighbor has some and I 
have to monthly keep hacking it out of my yard.  A four element quad for 
20-10 meters (three elements on 20 and four on 15-10) was built with bamboo 
spreaders, 1"x1" angle aluminum for the spreader to boom support and the 
boom made out of electrical conduit.  All the stuff was held together with 
hose and muffler clamps.  Ant. lasted until I took it down after three years.

The other quad was a four element as well, but it had two elements on 40 
(capacitive loaded), three on 20 and four on 15-10.  The spreaders were 
made out of central vacuum cleaner pipe and the boom made out of 3" 
irrigation pipe.  This ant. was destroyed when I cut a tree and misjudge 
where it would fall - yep, right on the ant.  The tree was being cut down 
to make room for a new tower so it wasn't a total catastrophe.  This ant. 
lasted two years.

At 02:06 PM 9/2/04, Jim Lux wrote:
>At 10:24 AM 9/2/2004 -0400, N4CW at aol.com wrote:
>>Being financially "challenged" and not having any reasonable sources of
>>aluminum for antenna experimenting, I thought of using CATV hardline as 
>>elements
>>(on perhaps a 6- or 10-meter yagi). I've got some 7/8" that I can use. It's
>>fairly rigid in short lengths.
>>Has this been tried before? Successfully?
>>If not, what are some potential problems? I just plan to ignore the center
>>conductor in the parasitic elements (but, I have thought of feeding the 
>>center
>>conductor in the driven element and allowing capacitive coupling to the
>>aluminum outer shield to transfer the r.f. with little loss.)
>>Thoughts and advice are appreciated.
>>Bert, N4CW/1
>
>Another fairly inexpensive way to improvise elements is to use multiple 
>copper wires on the surface of a cheap substrate (PVC pipe, wood, etc.) 
>It's an easy way to get a "fat" element which has other useful properties 
>(e.g. bandwidth).  For a 10m antenna you're looking at elements which need 
>to be about 8 ft long (sticking out from the center).
>
>Also, consider the idea of using truss and guy type construction to work 
>with floppy lightweight tubing (like "Schedule A" thin wall PVC).  Kind of 
>draggy from a aerodynamic standpoint, and not particularly durable, what 
>with UV, etc., but great as a support for experimenting.  You build the 
>mechanical structure once, and then just zip-tie wires to the struts.
>
>You might also be able to use that aluminum tape used for HVAC ducts on 
>the surface of something as a element. It's fairly inexpensive (50 yd, 2" 
>wide, runs about $10) and is around 3 mils thick.  Heck, aluminum foil and 
>glue might work.  Skin depth is pretty small at 30 MHz (about 0.0006" in 
>Aluminum), and most household aluminum foil is in the area of 0.001" 
>thick.  The rule of thumb is that if your layer is 5 skindepths thick, 
>then you've got more than 99% of the conductivity of a solid bar.  2 skin 
>depths is 86%
>
>(check out the on-line skin depth calculator at: 
>http://www.microwaves101.com/encyclopedia/calsdepth.cfm
>
>very handy)
>
>Jim, W6RMK
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         73,
         Mike, K4GMH