Sunday, August 15, 2010

Just put the finishing touches on a 75m BAZOOKA!

I used the upper end of the band for the designed area of operating and have a 2:1 SWR from 3.810-3.980

I used Belden 8267 for the coaxial section and the remaining portion of the antenna is made from the 10ga wire that my old dipole was made from.

This is the center support and insulator made from a PVC conduit T. 

I milled the "collar" from the bottom and mounted a SO-239 chassis connector and drilled the top for the eye bolt to hang it from.
After soldering the connections I glued the caps on.  I also put some glue on the outer jacket of the coax to help strengthen the antenna.

With the cover in place I taped the coax and caps together with electrical tape to help strengthen that area of the antenna. (The tape is not shown.)

To connect the wire to the coax, I cut about 3inches longer than needed.  I stripped the outer jacket and folded the braid back over the coax then I stripped the inner insulation off.  Next, I wrapped the inner conductor and wire end together and soldered.  Then I folded the braid back over that joint, twisted it, and soldered it onto the previous joint.

Time will tell if this is a mechanically sound antenna.  I was a bit surprised by the narrower bandwidth. The bazooka I built with RG-6 for 40m covers the entire band, but the entire length of it is RG-6 coax.


I have epoxy potted the center with 5 minute epoxy.  This helps to hold the coax in the conduit body and seals it from the elements.

The bandwidth is narrower than my 40m bazooka, which is to be expected.  It is the same for any antenna, as the frequency lowers the bandwidth gets narrow.  It is somewhat a function of length to diameter ratio.

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