Raised Vertical Height for DX

... Why “Higher” Can Be Worse on 20–10 m

For raised verticals on upper HF, “ideal height” for DX usually means keeping the base/feed region low, not roof-high. In Cebik’s upper-HF modeling notes, once the base gets high in wavelengths, the strongest lobe often tilts upward (especially on 10 m, and especially with 5/8λ radiators). Practical Antennas makes the same big-picture point from another angle: once the antennas are elevated and the current maxima end up at similar heights, a 1/4λ GP, a 1/2-wave vertical, and a 5/8-wave vertical often become surprisingly close.

What “ideal base height” means in practice

A DX-oriented practical target (for all three vertical types below) is to keep the base/feed region around 0.05–0.07 λ above ground ... high enough for clearance and symmetry, but low enough to avoid inviting a stronger high-angle lobe. (This 0.05–0.07 λ guideline is an inference from raised-monopole modeling trends, not a published hard rule.)

The heights below use free-space wavelength (λ ≈ 300 / f(MHz)), with typical band-center frequencies, and are intended as install targets ... not precision-cut “final numbers.”

How the DX angle tends to compare at those low bases

The table below uses practical “classes” of low-angle behavior ... not single-degree promises. The 1/4λ and 5/8λ raised GP columns align with the raised-monopole trend: as you keep the base low, the 5/8 can edge ahead at low angles, but the advantage is typically modest. The 1/2-wave EFHW vertical + LC sits between them in practice when the geometry is comparable and the feed/return path is kept clean.

Verdict by band

Here’s the tightened way to say it:

• Best pure low-angle DX: a 5/8λ raised GP, especially on 10 m and 12 m ... but the edge is usually modest when bases are already elevated.
• Best DX + size + sanity compromise: a 1/2-wave EFHW vertical with LC on 15 m and 17 m ... if you control the return path and choke the feedline hard.
• Best “value antenna” / easiest win: a 1/4λ raised GP on 20 m. Not the raw pattern winner ... but often the cleanest, shortest, least temperamental full-size result.

Vegetation Around Raised Radials ... Why Bushes Can Move Your SWR

For 20–10 m raised verticals with tuned/raised radials, bushes and plants matter mostly for one reason: your raised radials are part of the antenna. Anything close to them can detune the system and add loss ... and the effect often changes after rain (wet leaves and wet wood couple better).

What to aim for

• Do not let vegetation touch the radiator or the raised radials. Touching (or being just a few centimeters away when wet) often causes SWR drift and efficiency loss.
• You do not need to be “above all bushes” as a hard rule. You just need clear air around the current-heavy parts: the feedpoint area, the first meters of the radiator, and the radials.

Practical rules of thumb that work in real installs

• Keep ~30–50 cm clearance from bushes/leaves to raised radials and the lower part of the vertical. More is better, especially in wet climates.
• If bushes are dense/high around the base, the best fix is usually not “raise everything.” Instead:
  • keep the feedpoint low (good for DX angles), and
  • use small fiberglass standoffs/posts so the radials sit above the foliage and remain symmetrical.
• If a tree trunk is very close: try to keep the vertical a couple meters away if you can. Wet trees can couple and shift tuning; the bigger the trunk and the closer it is, the more “seasonal” your tuning becomes.

EFHW Vertical Return Path ... 4 Short Spokes Beats “Coax As Counterpoise”

EFHW verticals can be excellent ... but only when you treat the return current like a first-class design problem. If you provide no intentional return, the coax shield becomes it ... and then the antenna pattern, tuning stability, and RFI behavior become “whatever the installation decides.”

Four 0.025λ spokes vs one 0.05λ counterpoise

Compared with a single short counterpoise wire, 4 × short spokes (even if each is shorter) usually moves you in the right direction:

• More symmetry in the return path.
• Less incentive for the coax to become a radiator.
• Less “touchy” behavior with small layout changes.

Short spokes are still short spokes ... not “real” quarter-wave radials. Think “cleaner return path,” not “magic ground plane.”

Can those short spokes slope down?

Yes. For an EFHW’s short spokes, treat 20–45° downward mainly as a layout and symmetry choice. The practical priorities are:

• equal lengths,
• even spacing,
• kept away from lossy/metal clutter,
• and a serious current choke at or just below the LC box so the coax stops “helping.”

One important nuance:

• For a 1/4λ GP, drooping radials can be helpful (impedance control and “vertical-dipole-like” behavior).
• For a 5/8λ GP, aggressive droop is often not helpful at low angles ... flat or only slightly drooped radials are usually safer.

Spoke length cheat sheet

Using λ ≈ 300 / f(MHz). These are starting points ... trim and route for symmetry and clearance first.

Practical Picks ... If You Build One Per Band

• 20 m: 1/4 GP ... unless you’re willing to do the EFHW return-path/choking work to squeeze a little more pattern advantage.
• 17 m: 1/2 EFHW vertical + LC.
• 15 m: 1/2 EFHW vertical + LC.
• 12 m: 5/8 GP if the extra length is easy ... otherwise 1/2 EFHW vertical + LC.
• 10 m: 5/8 GP.

For the 1/2 EFHW vertical, the “secret sauce” is not mystery gain ... it’s return-path control and feedline isolation so the antenna behaves like the model, not like a random coax-and-house experiment.

If you want a “good enough” clearance target for your own yard: bush height and whether your radials are flat or ~45° down are the two inputs that usually matter most.

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