6BTV (or 5BTV or 4BTV) mod for 12 & 17 meter bands -- how to make a 7BTV or 8BTV, easy and cheap
 

The Hustler verticals are among the best.  OK, that's just my opinion, but it is shared by many!  :-)

There are lots of opinions and articles on how to best mount them, and how to do radials.  I'm not going to opine on the matter -- you can find plenty of info elsewhere.  Just so you know where I'm coming from, I have two of these antennas:  an elevated 5BTV with elevated radials, mainly used for 80m, and a ground-mounted 6BTV with on/in-the-ground radials, mainly used by the 2nd rig for digital and remote-control station contacts.  (See my page on how to bury radials for a vertical.)

In case you're not aware, these 3 models cover these bands:

You'll note the conspicuous absence of 12m and 17m.  (Sure, 60m and 160m are missing, too, but with no disrespect for those bands, they will not be considered in this article.)

Sure, you might get them to tune up on 12m or 17m, but they are more or less dead on those bands.  To make them come alive and work well, you have to do something physically to them.  My 6BTV sounded like a dummy load when I tried to receive signals on 17m -- but this easy mod really made it come alive.

There are several options to add the 12m and/or 17m bands:

  1. buy a fancy kit from somewhere like DX Engineering -- good stuff, I'm sure it works well, but not cheap -- don't misunderstand, I have some of their parts, and some of it is definitely useful (and they have great tech articles on it!), but I don't think you need to spend ~$60-70 to add just one band to the xBTV-series
  2. mod the original antenna by drilling holes and adding traps sticking out the side
  3. add a simple and cheap 1/4 wave wire to cover 12m and/or 17m

Since I wanted to be cheap (us pastors don't generally make a bunch of $), and since I didn't want to butcher the antenna, I decided to go with #3 above.  This isn't my brainchild.  Others showed me how, more or less, and those links are listed below.  So thanks to those guys!

Here is what I did.

First, you need these materials:

  1. ~6' - 7' of 1/2" electrical PVC
  2. about 6 or 8 black tie wraps, roughly 10" long
  3. good black electrical tape (Scotch 33 or 88)
  4. ~25' of copper wire -- you can use copper-clad-steel or hard drawn if you wish, but plain old #14 or #12 (solid or stranded) is perfectly fine
  5. a copper ground lug -- Home Depot SKU # 526-888(?) (Thomas & Betts BTC0208-B2); a pair of them is about $2:
       
  6. some good dacron/poly rope, or whatever rope you like for wire antennas -- probably only need 10-15' of it, give or take
  7. 2 egg insulators to transition from the wire to the rope
 

Steps:

  1. cut the PVC in half, so you have two pieces, about 3' - 3.5' each
  2. drill holes (bigger than your wire diameter) near each end of one piece of PVC (will go on bottom)
  3. drill holes (bigger than your rope diameter) near each end of the other piece of PVC (will go on top)
  4. attach bottom PVC to the top of the base of the antenna, using tie-wraps and maybe tape, as pictured below, with holes aligned so the wire will be vertical when it goes through them
  5. attach top PVC above the 20m trap of the 6BTV (it may depend on which model you have) -- make sure it is at least 13' above the bottom PVC, using tie-wraps and tape, as pictured  -- NOTE: be careful, don't fall -- I suggest a 12' A-frame ladder -- or if you want to tip the antenna, fine -- good idea to have a helper -- just be safe!
  6. cut copper wire -- 12m should be ~9' 5", 17m should be ~12' 11", but make them longer to begin with and allow for some to go around the egg insulators -- so start with about 10' and 13'6"
  7. at the bottom of the antenna, unscrew the main center (radiator) screw (don't lose the washers!), add the copper ground lug, lube the bolt, and then put it back together, as pictured
  8. attach the two copper wires to the ground lug (or you can do that before you install the lug) -- note that some hams will attach the wire on the aluminum tubing, just above the base -- you can do that, but make sure to think about the dissimilar metals, and either treat it or clean it often
  9. feed the 12m wire through one hole in the bottom PVC
  10. feed the 17m wire through the other hole in the bottom PVC
  11. attach egg insulators to the top end of each wire
  12. attach rope to each egg -- you'll need more rope on the 12m wire, because it is shorter
  13. up high on the top PVC, feed rope through the holes on the respective sides, pull snug (not too tight - it may help to pull them both snug at the same time, to avoid too much stress on the PVC), tie off by wrapping extra rope around PVC and using simple knot, make sure to leave some spare rope hanging for future adjustment (shortening the wires, if needed, will mean you need a bit of extra rope available)
  14. if yours is above ground, you may wish to add tuned radials for 12m & 17m -- that is up to you
  15. if yours is on the ground, you should already have a bunch of radials, so you won't need to add more
  16. check SWR, trim wires if needed
  17. go make some QSOs on 12m & 17m!!!

 

Here are a few pictures.  I just added the radials (see my page on How to Bury Radials), and you can see most of them are not soldered yet.  You'll also notice that 3 wires are coming out of the copper lug -- I added a 60m wire to see how it works -- I'm still testing that.

 

 

If you want to try to add a 44' wire to cover the 60m band (as I did), have at it.  Obviously, the top end of the wire won't be attached to the xBTV, but if you can attach it somewhere else (such as a tree), go ahead.  It may not be vertical, but the other guy will never know unless you tell him.

Or, for the 4BTV and 5BTV (which don't have 30m), if you want to add a 23+' wire for the 30m band, great.  I've never done it, but I don't know why it wouldn't work.

What does this do to the radiation pattern of the vertical?  I could only guess.  However, we're not building a 5-element monobander here.  We're using a good antenna but also a compromise antenna, and we're adding a band or two to it, not thinking that it will outperform anyone's Yagi, but with the goal of getting on the air and having fun.  And getting on 12m and/or 17m (along with all the original bands) will be very easy with this cheap & simple mod.

Oh, if you haven't done this already, don't forget to decouple your feed line from the antenna.  Yes, for a ground-mount you can bury the coax a bit (and that is good), but most folks recommend a choke/balun, otherwise your feedline will tend to radiate.  You can buy one made for a vertical, (over $100), or you can make an air choke pretty easily.  Some call it the "Big Ugly Balun".  See my web page on the "BUB".

 

Good links:

K7TUC 4BTV mod (good info)
Here is how M1KTA did this to his vertical
KL7JR did it this way (you may notice that mine is quite a bit like his)
Ham Universe article on their version of this mod

 

73, Dave, N0RQ

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