BAD BALUN SUMMARY
The world is not flat and single-core 4:1 Guanella "Baluns" do NOT work!
If you have stayed with me to this point, then you should have read the arguments suggested by several experts, as well as reviewed the test results of my own tests. All of these reached the same conclusion.
Here is a summary of the points you should have learned:
- The 4:1 Voltage balun (by itself) is never a good balun to use in an antenna because it does a very poor job of rejecting common mode current. Rejecting CMC is the primary task of any balun.*
- The common 4:1 Guanella "balun", wrapped with both transmission lines on a single core DOES NOT WORK. PERIOD! In fact since it always forces a voltage imbalance with non-floating loads, it is not a balun at all!
- The 4:1 Guanella balun, wrapped on dual toroid cores with each transmission line on its own separate (dedicated) core is indeed the balun of choice for matching balanced (non-floating) loads to unbalanced coax - for loads of 200 to 300 Ohms.**
* Several people have suggested combining a 4:1 (or 6:1) Voltage balun with a 1:1 Guanella choke - a device often referred to as a "hybrid balun" - and using for this purpose. All (that I have seen) have reported good results with this combination. I have not yet tested this myself and my only comment is "I hope they are right."
** This is only adequate whenever the common mode current is not too aggressive. Things like high SWR or using radical feedline splits can cause excessive common mode current. In that case you will need a 1:1 common mode current choke in addition to the 4:1 Guanella balun. Normally a W2DU choke will suffice. In hard-neck cases you will need a 1:1 Guanella choke.