Design Your Own J-Pole Antenna

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Home of the RASCAL"

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SAVE TIME BY USING THE HANDY J-Pole CALCULATOR BELOW.


NOTE: Coax center conductor attaches to the "Long section" feed point.
Shield attaches to the short section feed point.

Enter Antenna Operating Frequency

    Freq MHz

A (Long section) dimension is:    feet,        inches,        meters

B (Short section) dimension is:    feet,        inches,        meters

C (Feed point) dimension is:         feet,        inches,        meters

D (Spacing) dimension is:             feet,        inches,        meters

Inside (spacing) dimensions are metal to metal measurements, NOT center to center.

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Click here to view an alternate method for feeding a VHF copper "J-Pole"

CLICK HERE for a "close-up" of the alternate J-Pole feed method.

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BUX BALUNs should be installed at the antenna feed point, or where the coax or feed-line attaches to the above ground antenna.  BUX BALUNs are used to connect balanced antennas to unbalanced transmission lines, such as coax cable.  Their primary purpose is to prevent antenna (RF) currents from flowing down the outside of the cable.  Another function of the BUX BALUN41 is to match the impedance of an unbalanced coax to the balanced feed point of a balanced input antenna(s). BUX BALUNS may also be used as “line isolators” anywhere along the cable to prevent the destructive influence of induced RF currents (VSWR).

BUX 1:1 BALUNs are current BALUNs. They consist of several large, number 73, ferrite type 44 cores.  BUX BALUN11 operate from 3.5 to 72 MHz and allow use of RF power to the rated capacity of the BALUN.
 

BUX 4:1 BALUNs are voltage BALUNs. They consist of a large, number 41, ferrite dough-nut bobbin.  BUX BALUN41 operate from 3.5 to 55 MHz and allow use of RF power to the rated capacity of the BALUN.

 

Our BUX 4:1 baluns may also be used to transition 50 ohm coax to twin lead or ladder lines.

 

At BUX COMM, *We don't cut corners!
The components used in the manufacture of our BALUNs are from top quality components, beginning with the Silver Plate SO239 connectors and center insulator is made of teflon™(E.I Dupont). The wire we use to wind the ferrite donut is heavy-duty, silver flashed wire, with teflon™ insulation that will handle RF voltages above 5000 volts, and temperatures above 2000 degrees. The binding posts are heavy-duty, tempered brass, with end holes and side-thru holes to accommodate either type loop-thru connection. A double-shoulder brass capture nut is used to add a secure bite and improve antenna wire electrical connections.  With our BUX UN UN (ONION), the coax is Belden™ and the PL259 connectors are Amphenol™. 
4:1  Balun,  BUXBALUN 41   $19.95

o 50 ohm, SO-239 unbalanced input
o Balanced output
o 1.6 to 50 MHz
o Toroid (Voltage) design
o Heavy Duty, Lightweight construction
o Sealed against moisture
____________________________________________________

1:1  Balun,  BUXBALUN 11  $19.95

o 50 ohm, SO-239 unbalanced input
o Balanced output
o 1.6 to 50 MHz
o Toroid (Current) design
o Heavy Duty, Lightweight construction
o Sealed against moisture
____________________________________________________
BUX UN UN De-Coupling transformer, similar to above, but has SO-239 (female)
input
connector and output connector is 1 ft Mini 8 cable with PL-259 (male).

 BUX ONION  $19.95 


4:1, 1.5kw Balun,  BUX BALUN 41HD  $27.95
Toroid  design, wound with teflon covered, silver plated wire.* Heavy-Duty, construction.

1:1, 1.5kw Balun,  BUX BALUN 11HD  $27.95
Toroid  design, wound with teflon covered, silver plated wire.* Heavy-Duty, construction. 

 

1:1,  1 kw VHF Balun,  BUX BALUN 11V  $24.95
Toroid  design, wound with teflon covered, silver plated wire.* For VHF beams and J-Pole applications, construction. 

BUX ONION  Decoupling Transformer
BUX UN UN De-Coupling transformer, has SO-239 (female)input connector and output connector is 1 ft Mini 8 cable with PL-259 (male).
 BUX ONION is and UNbalanced to UNbalance (UN-UN) decoupling transformer designed to be used specifically with the DBLSPCL antenna.

 High RF currents traveling along the coax feed-line shield can cause high VSWR.  This decoupling transformer prevents RF currents from traveling down the outer shield of the coax.

The input connector is an SO239 (female) and the output connector is a PL259 (male), which mates the connector of the "DBLSPCL" RV/Apartment dweller antenna shown above.

BUX ONION  $19.95 

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 600 ohms at the end of your 600-ohm line. That only happens if you have a 600-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 12:1 balun. Use a 4:l BALUN and your system will work just fine.  

You can read Kurt N. Sterba “AERIALS” column in World Radio Magazine.

BUX MOBALUN
When you hear those strong HF mobile signals, here's one reason they stand out from the rest.
By installing the BUX MoBalun near the input to your antenna, you deliver more RF energy to the antenna. At the same time, the BUX MoBalun prevents RF from traveling back along the shield (high SWR) of your coax. High power rating, Low-permeability toroid, with Internal composition fiber-glass to prevent vibration during mobile operation. For input and output connectors, we use only the best Silver plated, Teflon insulated, SO239 connectors. 700 watts PEP. Our MoBALUN is also ideal for marine antenna installations.
 

$19.95  MOBALUN 

ANTENNA  INSULATORS

Weatherproof, (TENYTE) insulators.  Perfect for your DIPOLE or Windom antenna.
For the apartment dweller, you can now hang the 20 meter doublet
in the attic.   I've QSO'd with stations all over the world with the
33 ft dipole in my garage attic.   One insulator at the center, and one each end.  

It's great for other HF WINDOM and single-band dipole antennas.  Dielectric strength is comparable to the old ceramic insulators, without susceptibility to cracking or breakage under impact or extreme temperature changes.
Package of  3,  $2.99 
 ANTINSL3               Package of 10, Insulators $8.99, ANTINSLX10