Design your own J-Pole Antenna

BUX BALUNs   should be installed at the antenna feed point, or where the coax or feed-line attaches to the above ground antenna.  Important Notice;  WHY USE A  4:1 BALUN Krusty Olde Kurt is now going to repeat himself.  Why? Because the same question keeps coming up over and over. And he wants everyone to get it right.   "I'm feeding my dipole with 600-ohm line.  At the station end I need a balun to convert to 50-ohm coax. I need a 12:1 balun, right?"   Wrong!  A 4:1 balun would be better. Why is that?  If your dipole is up, let's say, 35 feet then on 80 meters it will probably have a resistance at resonance of about 40 ohms. The actual resistance depends on the height above ground in wavelengths.  If the dipole is 40 Ohms then what do you see at the transmitter end of your 600 ohm line? If the line is a half-wave long (120 ft on 80 Meters) you'll see 40 ohms.   Remember, a half-wave line repeats what it sees at the other end.  But if it is a quarter-wave long you'll see 8500 Ohms!  At other line lengths you'll see impedances somewhere between these two extremes. So you are not going to see 450 ohms at the end of your 450-ohm line. That only happens if you have a 500-ohm antenna hooked onto it. With such a variation in impedance at the trans­mitter end of the line there is no one balun transformer that will match it. Most of the time the impedance will be above the 50 Ohms of your coax so a high impedance balun would be desirable.  Unfortunately high imped­ance baluns don't work well when not matched.    Experience has shown that 4:1 baluns work best in this service.  They are more rugged and will take bad mismatches especially if they are wound on an iron powder core.  So stop searching for that 9:1 or 12:1 balun. Use a 4:l BALUN and your system will work great.   You can read Kurt N. Sterba “AERIALS” column in World Radio Magazine. Order Line ONLY, Mon > Fri 10 AM to 4 PM,  434 534 8873  or FAX your order, 24/7 to FAX 434 525 7818 ←BUX  Master-Match™  Balun 1:1  $24.95   MM11  BUX  Master-Match™1:1 Baluns are ideal for Dipoles, Slopers, Inverted-Vees and center feed-point, RV antennas. They are also employed at the driven element of of many HF beams and Quads, and where feedpoint impedance is at, or near 50 ohms.  By equalizing the currents in the antenna feeders, the Dipole pattern improves and prevents feedline (re)-radiation by preventing antenna currents flowing along the outer braid of the coax transmission line. Includes three FREE antenna insulators (shown elsewhere, this page). ←BUX  Master-Match™ Balun 4:1   $24.95    MM41    Our BUX  Master-Match™4:1 Balun is ideal for matching windoms, web'd or folded dipoles, and antennas fed at a 250 ohm to 500 ohm impedance feedpoint with normal 50 or 75 ohm coax cable.  In contrast to ordinary Baluns the BUX Master-Match™4:1 Balun support balanced currents in each leg of the antenna and prevents feedline (re)-radiation.   As mentioned in our windom articles, feedlines and 450-ohm, brown, poly-covered ladder-line are easy to handle, and more-over they present another efficient means to feed multi-band antennas.  We strongly suggest the use of our PolyCoat-Ladder-Line as it is made of strong, copper-clad, steel conductors.  This light but durable, PolyCoat-Ladder-Line will far outlast the normal open copper with plastic spacers.  (Includes three FREE antenna insulators, shown elsewhere, this page). The Got’cha is;  These open type feedlines can bring high RF voltages into the shack.  By using BUX  Master-Match™4:1 Balun near the point where the transmission line enters the HAM shack, we impede that lip-bitting voltage and prevent excessive RF from getting into the PC, the transceiver, the telephone, the television (the XYL is watching) and heaven-forbid, the computer on her automatic washer. The BUX MasterMatch™ 4:1 High Performance , 1.5  KW Balun (if SWR is less than 2:1)  *CW/SSB duty-cycles only.     SSB/CW Power @ 3.5 MHz* >1.5 kW if SWR is less than 3:1  *Not rated for AM, RTTY or other high duty-cycle digital modes. Double-co-efficient coupled design. Exceptional High output. Large ferrite cores. Non-core saturating design. High winding reactance with only a L-C compensation. Hi-Temp insulated, large gauge, high temperature, wire. Compensation for wide bandwidth Rated above the legal power limit. Stainless-steel eyebolts. Input Connector SO-239 Output Connector Hard-Drawn, tempered Brass Binding Posts. Bandwidth 160 - >10 m.

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 All text and graphics on these pages are ©®™ of G. E. Rogers Sr and BUX COMM Corp 1986 - 2005