Topband: Topband Digest, Vol 116, Issue 49

[Tom W8JI]

> IMHO you are much better using a ballanced tuner with an UNUN on the 
> transmitter side.

http://www.w8ji.com/tuner_baluns.htm

Apparently the balun's action was never fully thought through before 
articles suggesting baluns on tuner inputs were published. Everyone just 
went with off-the-cuff first impressions.

Moving a balun to the tuner input works best if the tuner already did not 
need a balun in the first place.   :-)

There are balanced tuner tests on this page at the bottom:

http://www.w8ji.com/balun_test.htm

This shows a 1:1 current balun of good design on the tuner output is every 
bit as effective as a commercial "balanced" tuner, the E.F. Johnson KW 
Matchbox.

It also shows how a 4:1 "current" balun on a single core (from "Baluns and 
UNUN's"), which is actually sold commercially as a balun and used in some 
high-end tuners, is not a balun at all!   A single core 4:1 current balun 
will actually force a system into gross unbalance!

I have a friend with a high-dollar motor-driven autotuner who had incurable 
RFI in his house on various bands with high power. He altered the feedline 
length, moved things around, and added grounds without success. When we 
looked at his tuner, it had a single core 4:1 current balun. Rewinding the 
same core to a 1:1 current balun cured his problems entirely.

73 Tom