Ham Radio

Saturday, November 24, 2007
Homebrew 40/80 Trap Dipole Design


This Antenna design was one that I used about 4 years ago, it worked exceptionally well on 80m and 40m. The size of the antenna makes a Half wave length on 80 meters, and with the traps a half wave on 40m with a SWR (standing wave ratio) of 1:1-1.5 across both bands.

It worked well also on 20m with the use of an A.T.U (antenna tuning unit).

I made my version of this antenna using 3mm multi strand copper cable which I left covered by the PVC insulation.

The traps can either be home brewed using some 40mm diameter plastic drain pipe and winding wire around the pipe approximately 10 turns, then connected in line after the 10 metre lengths. Or the alternative is to purchase some commercially made 7.1 MHz traps, and fit them in line the same way.

The antenna can be fed with 50 ohm coax with a home brew balan or again a commercially purchased balan.

The wire lengths of the dipole are 2x 10 metres and 2x 6.7 metres as shown on the diagram above.

This antenna can be mounted quite low to the ground if you wish to produce a high angle of radiated signal which is good for distances of 0-1500 km.

For DX work a lower angle of radiated signal can be obtained by mounting the antenna 10 metres or more above the ground. The higher the better!

If you get chance to try this simple design, I am sure you will not be disappointed.

Good luck and hope to hear you on the bands.

de 2E0HTS 73

posted by Simon Davison @ 5:21 pm  
4 Comments:
  • At 8:43 pm, Blogger Jorge said…

    Hi Simon, thanks for the traps dipole design.
    "The traps can either be home brewed using some 40mm diameter plastic drain pipe and WINDING WIRE around the pipe approximately 10 turns, then connected in line after the 10 metre lengths."
    What diameter of wire I will need for the coil?
    regards
    73`
    Jorge
    LU8HRW

     
  • At 11:54 pm, Blogger 2E0HTS Simon said…

    Hi Jorge

    try using the same wire that you are using for the dipole legs (2mm) It really depends on how much power you will be running. 2mm and above is more than enough when using up to 200W. I run 50W and can get away with wire at 1.5mm but 2 - 3mm is best.

    Good luck and hope we hear each other on the bands.

    73 Simon

     
  • At 6:23 am, Blogger Andrew Janetzki said…

    Hi Simon,

    I had a go at constructing the 80/40 trapped dipole but have failed. I tried shorten and lengthening the legs a fair bit to bring the SWR down with no success. I believe the fault may be in the coil/trap as I replaced your designed trap with a coaxial version I made some time ago which gave me much better SWR results.

    Not sure where I may had gone wrong as I had followed your design as written.

    73
    Andrew
    VK3FAPJ

     
  • At 4:19 pm, Blogger 2E0HTS Simon said…

    Hi Andrew

    good to hear you have successfully built the antenna. I guess the coax is a more closer match for the impedence of the dipole wire that you decided to use. Hope to hear you on the bands soon and get a QSO with you!

    Best 73 and happy DX. de Simon

     
Post a Comment
<< Home
 
Custom Search



 
About Me

Name: Simon Davison
Home:
About Me:
See my complete profile
Previous Post
Archives
Links
Powered by


free counters
>
BLOGGER