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Πέμπτη 30 Ιουνίου 2011

Φορητή κεραία μεσαίων

I wanted a good 160m antenna to work stations while static mobile. After finding out that a commercial one was around £50 I decided to make one. The only expense was a reel of enameled copper wire of .75mm which was less than £10 & had enough wire to make at least 2 coils for 160m with enough spare for an 80m coil.

 Other bits were all found in my garage/workshop, such as some old alloy tent poles & a piece of plastic water pipe. 
                                                
To mount my antenna, I had a friend make me a piece of stainless steel tube , 6 ½” Long by 1 1/8” diameter external & approx ¾” internal diameter. The tube had a 3/8” thread at the bottom to connect to a mag-mount.
  This would allow the antenna with a base tube of less than ¾” diameter, to be mounted to the car.

 The antenna was made using 4 alloy tubes, 1 plastic tube & a 5 foot whip. Once constructed, the antenna would split into two pieces for storing in the car.

  The bottom 2 feet of the antenna was made using 2 pieces of tubing, one nested inside the other. Then I nested a 2 foot length of water pipe over the bottom section. The water pipe was just over ¾” diameter & the tubes were drilled & had a nut & bolt fastened through them so they would remain rigid. Finally I added another one foot of aluminum tubing. This would be one half of the antenna.

   The next half of the antenna was another piece of tubing, just over 2 feet long, with a whip stud fitted so I could use a five foot or six foot whip at varying heights to enable full coverage of 160m.

   I wound about 115 feet of the .75mm enameled copper wire onto the plastic former.
This was close wound & taped on. The ends of the wire were attached to the top & bottom of the aluminum tubes either side of the plastic tube. Then the coil was covered in some blue heat shrink to seal it.

When operating, I found the total height of the antenna was about ten foot tall on my local net frequency of 1.972 MHz   . The antenna was taller than this when used in the DX window, around 1.845 MHz  

  This antenna works well for me & I have worked stations all around the UK & Europe so far. I am currently working on a base loaded antenna for 160m. The antenna was a homebrew one which only stood about 5 feet tall. I’m going to take some wire off the coil so I can gain some height by using a larger whip.

  Check out the pictures of my Homebrew mobile antenna. I also plan to make one for 40m in the future. This will be made so that I can use the top alloy tube & adjustable whip from my 160m antenna. I hope to make the antenna about the same overall size. A smaller coil will be the main difference.

Aerial Support

Base Section

Centre Section Former

Centre Section Coil

Centre section Heatshrinked Coil

Top section

Whole Aerial

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