BUDDIPOLE IN THE FIELD

The table above may not be the final story as verticals deployed over or
near saltwater show significant gains over those listed here (that assumes
“average” ground). For bands 10m-15m, the dipole on a 16 foot mast is
probably the best choice, but it becomes much less clear for 17m and
20m. For 30m and 40m, the vertical is the obvious choice.
There are a few final points that should be made before proceeding to
the cookbook section. The typical feedpoint impedance for a horizontal
dipole in free space is 70 ohms. A ¼ wave vertical is half a dipole and
has half the impedance (something in the neighborhood of 35 ohms)
when there are no other losses and when the antenna is full-sized.
Buddipole verticals will have those extra losses through the ground as they
will not be deployed over perfect ground. And, some Buddipole
configurations will be smaller than full-sized antennas so the radiation
resistance will be much lower than that of a full-sized antenna. Both
affect feedpoint impedance.
If an antenna were to present 25 ohms impedance at the feedpoint, and
our radio is expecting 50 ohms, then a 2:1 ratio transformer, matching
the 25 ohm load to our radio,
would be ideal. Or, if the antenna
presented a 12.5 ohm load, then
a 4:1 ratio transformer would
match the load to the 50 ohms
expected by the radio. Both
translations are possible with the
Buddipole Triple Ratio Switched
Balun (TRSB).
The switch on the TRSB allows Triple Ratio Switch Balun
the user to select 1:1 (50 ohms to
50 ohms), 2:1 (50 ohms to 25 ohms), or 4:1 (50 ohms to 12.5 ohms).
Verticals will often present less than 50 ohms at the feedpoint so this
box is very handy for deploying vertical antennas.
There is another issue with vertical antennas worth discussing. Radial
wires are wire elements that are connected to the “cold” side of the coax.
The power runs down the coax traveling on the outside of the center
conductor and the inside of the braid of the coax. The outside of the
braid looks like a third conductor at HF frequencies. What keeps the
power from just following the outside of the braid back to the radio?
The Buddipole standard coax (in either 25 foot or 50 foot lengths) has
beads on the coax near the banana plug leads that help stop RF current
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