The KISS Balun
Since the purpose of the balun is to prevent antenna current from flowing on the outside of the coaxial feed line, why not do it the easy way and eliminate the resistance of the windings in the windings of the ordinary balun? Let’s not use any windings at all! The concept for the KISS balun is simple and was introduced to ham radio by Walter Maxwell, W2DU, in 1983. It is also known as the bead balun and it works very well.
We can prevent antenna current from flowing on the outside of our coax by simply winding the coax into an rf choke. This system is quite effective and is used on at least one popular beam sold to the ham radio fraternity today. The problem with this system is that it causes the coax to distort and thereby makes an impedance “lump” in the line. This problem is greater in the modern foam coax than with the older solid dielectric types of yesteryear.
A better solution to the balun problem can be found at many swap meets in the form of ferrite beads that will fit over the outside of the coax feed line. The beads need to have a hole just a bit larger than the outside of the coax and you will need about 50 of them for the low frequency bands, less for the higher frequencies.
I have been experimenting with such a balun with good success. I use RG-8X coax and beads of unknown characteristics that were obtained from the junk box. All seem to work about the same and it seems to make no difference if the beads are strung out at intervals along the feed line or if they were all placed next to each other in a line in groups of 5 or so. I use a counterpoise under the antenna and measure the current flowing in that device to determine the balance in the system.
From Editor, K5CNF
The next useful item Bill passes on to us is a small program for the MFJ-202B antenna noise bridge. It is written in BASIC and Bill states that while he has used it enough to feel it is accurate enough for general use, he would like folks to check it out on their equipment and verify it. Remember in the days of the paper magazine, you would need to sit down and tediuosly enter the lines and lines of program, make little mistakes, fix, more fix, try to run, try to run, and debug and debug. Now, with this wonderful new technology, all you need to do is capture the code to your clipboard right off this page, save to file and Voila! So, here is the program listing for GW Basic:
10 CLS
20 CLEAR
30 COLOR 14,0
40 PRINT "NOISEBR.BAS"
50 PRINT "A PROGRAM FOR THE MFJ-202B"
60 PRINT "BY W6TM"
70 PRINT
80 INPUT "ENTER FREQUENCY IN MHZ";F
90 INPUT "ENTER RESISTANCE IN OHMS";R
100 INPUT "ENTER REACTANCE DIAL READING";D
110 E=0
120 INPUT "IF USING EXPANDER, PRESS 1. IF NOT, PRESS 0";E
130 IF E=1 THEN GOTO 500
140 IF D<=0 THEN GOTO 170
150 IF D>0 THEN GOTO 180
160 'CALCULATE REACTANCE - OR +
170 X=(888/F)-(160000!/(F*(180-D)))
180 X=(888/F)-(160000!/(F*(180+D)))
190 LET R=INT(10*R+.5)/10
200 R=ABS(R)
210 PRINT "Rs = "; R; " OHMS"
220 LET X=INT(10*X+.5)/10
230 PRINT "Xs = "; X; " OHMS"
240 Z=SQR(R^2+X^2)
250 LET Z=INT(10*Z+.5)/10
260 Z=ABS(Z)
270 PRINT "Z = "; Z; " OHMS"
280 A=SQR((R+50)^2+(X^2))
290 B=SQR((R-50)^2+(X^2))
300 S=(A+B)/(A-B)
310 LET S=INT(10*S+.5)/10
320 S=ABS(S)
330 PRINT "SWR = ";S
340 Q=X/R
350 LET Q=INT(10*Q+.5)/10
360 Q=ABS(Q)
370 PRINT "Q = ";Q
380 H=R^2
390 G=X^2
400 J=(H+G)/R
410 LET J=INT(10*J+.5)/10
420 PRINT "Rp = ";J "OHMS"
430 K=(H+G)/X
440 LET K=INT(10*K+.5)/10
450 PRINT "Xp = ";K "OHMS"
460 PRINT
470 PRINT "TO CALCULATE ANOTHER VALUE PRESS [F2]"
480 GOTO 570
490 'CALCULATE X & R WHEN USING EXPANDER
500 V=(888*D)/(F*(D+180))
510 'V=Xeq
520 T=(200*(200*R-(R^2)-(V^2)))/ ((200-R)^2+(V^2))
530 'T=Ru
540 X=40000!*V/((200-R)*(200-R)+(V^2))
550 R=T
560 GOTO 190
570 END
Editor, K5CNF: So try it out and see if it will do the job for you and, one last note from Bill.
“If you have a similar system or experience, why not share it with the fraternity.” This is what antenneX is here for.W6TM
Originally posted on the AntennaX Online Magazine by W.R Booher, W6TM
Last Updated : 15th March 2024