big ugly balun

The Big Ugly Balun (BUB)
 

Big & kinda ugly.  That describes me  :-)  — and it describes the big ugly balun as well.  Thankfully, we (both me & the BUB) work pretty good.

If you use a vertical for HF, or if you use a coax-fed dipole of some sort without a balun, you’ll want to consider this.

I’m not going to reproduce all the technical why’s — others can do that much better than I can — see the links below.  But I do want to show can a BUB can be built and used from a practical perspective.

You’ll need:

  • 23-25′ good quality coax (such as LMR-400)
  • a form to wrap it on (such as 4″ PVC, about 1′ long)
  • 10 or so black plastic tie wraps (10-14″ long)
  • you’ll probably want to put PL-259 on one or both ends
  • when completed, you may wish to wrap the whole thing in good electrical tape (Scotch 33 or 88), depending on how well you did the tie wraps
  • drill and drill bit the diameter of your plastic tie wraps

Steps:

  • cut coax to length (23-25′)
  • (it may be useful to have a 2nd pair of hands for the wrapping of the coax)
  • starting near the bottom of the PVC, drill single hole for plastic tie wrap
  • put tie wrap in hole
  • put 1 or 2 turns of coax on bottom of PVC — it is probably helpful to turn the PVC, not twist the coax
  • carefully drill 2nd hole above the top of the coax
  • put tie wrap through 2nd hole, holding coax snug, tighten tie wrap
  • make some more turns of coax, drilling hole after 3 to 5 turns, installing tie wraps as needed
  • a little over halfway through, the tie wraps will no longer be long enough, so you’ll start them halfway up
  • after 20-21′ is on the PVC, add any more tie wraps if needed
  • wrap with electrical tape if needed
  • install PL-259 end(s) if desired
  • if it will be for a dipole, add dipole PVC and/or hooks if desired — see http://www.hamuniverse.com/aa4cvfandipoleIMG_22a.jpg
  • drill any support holes at the top, if needed
  • install — keep the BUB away from direct contact with metal — keep it at least a few inches away from any metal tower/pipe/support

Here is my BUB under my full-1/4-wave 40m vertical, held up by some dacron/poly rope:

  

Good links:

Ham Universe on the BUB (very good explanation, lots of pictures)
Ham Universe with a BUB under a multi-wire dipole support 
 

 73, Dave, N0RQ