[TenTec] Bob's Monster Balun With His Tentec Radios

[Robert & Linda McGraw K4TAX]

As several on the reflector have asked, here it is.  And thanks for asking.

 The monster balun, often referenced as "the ugly balun" is made of some 18 
to 20 ft of RG-213 coax, close wound on a piece of 3" OD PVC.  The RG-213 
coax is preferred because of the solid dielectric.  (A foam dielectric cable 
being put in a tight wound condition will allow the center conductor to 
migrate inward and eventually short to the shield.)  The idea is to have as 
many turns possible as opposed to larger diameter turns.  These should be 
flat wound carefully side-by-side.  Getting much smaller than 3" makes 
winding and working with the project more challenging.  Feed one end as 
though it is 50 ohms unbalanced and the other end as a balanced feed.

 For construction, I typically drill a couple of holes about 1" apart in one 
end of the PVC to use as terminals for the balanced feed point, fitting them 
with some brass bolts, washers and nuts.  I use wire lugs on the shield and 
center conductor of the coax, both crimping and soldering them in place and 
placing them under the nuts of the screws.  This will hold one end of the 
coax securely.  If you intend to use the balun outside then be sure to use 
some duct seal or some other water proofing method to assure that water will 
not get into the open end of the coax.  Then wind the remainder of the coax 
on the PVC form.  At the end, drill a couple of holes through which I pass a 
zip tie or wire tie to secure the other end, leaving a pigtail of 6" to 12". 
To that end I install a PL259.  Now you have the "ugly balun".

 I've measured the balance with this configuration at multiple frequencies 
between 1.8 MHz and 30 MHz to find quite a good balance regardless of the 
load Z or reactance posed to the balanced end.  As to power handling, the 
rating of the coax is it.  For RG-213 this is higher than most hams can 
generate in watts.  I usually mount the balun at the base of the tower being 
sure to keep it away from the tower by the length of the coil or more. 
Usually about 18".  The coax goes to the tuner in the house.

In all frankness, I prefer to bring the balanced feed line direct into the 
operating position where it is attached to the "ugly balun".  The pigtail is 
then attached to the tuner which is a Tentec 238 L network.

If you have any questions or need additional information on balanced feeds, 
various tuners and such, ASK.  I prefer to NOT take up space and time here 
on the reflector with the topic but be assured I will answer each and every 
e-mail to the best of my abilities.

 73
 Bob, K4TAX