Optimal Buddipole Antenna

 Antenna Construction

This is the Buddipole vertical antenna made specifically for 20 meters. The antenna consists of the following parts (Buddipole part numbers shown in parenthesis).

1) Buddipole tripod mount (BPT),

2) Buddipole 16 foot mast (BML),

3) VersaTee interface to antenna element where guys attach (VTE),

4) 3 sections of 24" mast (XAA) plus the long telescopic whips (black) vertical fully extended (LTW),

5) 2 counterpoise guy wires cut to 16.5 feet and a third guy made from Dacron rope (The Wireman, #816).

The counterpoise wires are the 2 wires joined together at the midpoint of the antenna structure, joined onto the VersTee black terminals. The two counterpoise elements are made from 3/16" copper woven rope (wire) with a black UV resistant Dacron covering. The tensile strength for this woven wire is stated as 770 lbs so it should hold up the antenna in higher winds. The wire can be purchased from The Wireman using their part number No. 816.

   

                   Buddipole VersaTee

 

Note that the wire rope is fed through the end insulator, knotted, heat shrink tubing applied and then terminated in a 3/8" diameter ring lug.

This method removes all stress from the ring lug and keeps it on the wire rope where it belongs.

VersaTee with Top Insulator and Wire Rope. Bolts on each end are 3/8" dia. x 1/2" long plus lock washer, stainless steel

 

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 Alternate Configurations

 

One interesting variant is to use an alternate feed line and connect the black and red terminals so the counterpoise actually becomes an inverted-vee antenna. By switching feed lines between the vertical element (blue terminal on VersaTee) and the red terminals, an effective Vertically / Horizontally polarized antenna can be created. This should allow for optimization between DX / NVIS operations, respectively.

 

Double feed lines can be brought down the mast or a small relay can be used to select between the two antenna - your choice. A feed line length of an electrical quarter wave can also be chosen and the coax end left unterminated (which is an open circuit). The open circuit translates to an electrical short at the red and black terminals. If this technique is selected, the relay must disconnect both center conductor and shield of the inverted-vee feed line. I hope to gather some S-meter data between these two configurations to demonstrate if this is an effective choice for the ham radio operator.

 

                                      Completed Optimal Buddipole Used During Field Day

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 Antenna Tuning

Antenna tuning is accomplished by folding back the counterpoise end points so the overall length is varied. Folding back the elements allows for the overall length to be adjusted shorter or longer as needed during the tuning process.

The ends of the wires feed through an antenna insulator appearing white in the photo above. Once folded back, UV resistant tie-wraps are used to secure the wire to itself keeping the chosen length constant. By symmetrically adjusting both counterpoise elements at the same time and then taking a VSWR measurement, the antenna resonance can be optimized for the 20 meter band. I had no problem getting the antenna to resonant over the entire band that was an easy impedance match for my transceiver.

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 Antenna Storage

One thing about wire antennas is the fact that they can be easy to store. The Optimal Buddipole can be rolled up onto a cable spool that is found at your local Lowe's or Home Depot. It is commonly used to roll up power extension cords. Just roll it up and put it away until it is needed on another day.

                            Roll-Up Antenna Spool

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