Why We Use One- or Two-Piece HF aluminium Radiators

…instead of thin, multi-section whips

We’re often asked:
“Why do you use 3 cm (30 mm) diameter, 2 mm thick aluminium poles for HF, instead of slimmer antennas made of several pieces?”

For HF (3–30 MHz), the answer is simple: efficiency, bandwidth, and long-term stability. On the lower HF bands especially, every fraction of an ohm of extra loss in the radiator or its joints directly eats into your radiated signal.

HF Is Unforgiving To Loss

HF antennas are usually short compared to the wavelength, especially below 10 MHz. That means:

• The radiation resistance is low to begin with
• Any extra loss in the radiator or joints is a large percentage of the total

On VHF or UHF you might “get away” with lossy sections and sketchy joints. On HF, that same resistance can easily cost you several dB of radiated power. A small amount of loss that would be invisible at higher frequencies can be the difference between being heard or not on 80 m or 40 m.

That’s why we deliberately use a single thick aluminium radiator wherever possible: to keep the ohmic loss in the high-current path as low as we realistically can.

Thick HF Radiators Improve Efficiency

Even at HF, RF current concentrates near the surface of a conductor (skin effect). A 30 mm tube has far more surface area than a thin whip, so its RF resistance is lower over the same length.

Because HF antennas on the low bands start with a modest radiation resistance, adding just a few tenths of an ohm of loss in the radiator can mean:

• Noticeably less power actually radiated
• More input power wasted as heat instead of signal

Using a thick, one-piece (or carefully designed two-piece) radiator keeps the loss resistance very small compared to the radiation resistance, which directly improves your real-world efficiency on the air.

Why Multi-Section Whips Are Inherently Lossy On HF

Every joint in a multi-section HF whip introduces:

• Contact resistance (even when new)
• Corrosion and oxidation over time
• Performance drift with weather, vibration and repeated assembly

On an electrically short HF radiator, this extra resistance is effectively in series with the radiation resistance. You pay for it directly in lost efficiency. A one-piece radiator eliminates these joints in the high-current path entirely.

If we use a two-piece design, we keep a single, robust joint in a controlled location, with large contact area and secure clamping, to keep that added resistance negligible.

Element Diameter And HF Bandwidth

HF operators rarely want a razor-sharp, single-frequency antenna. Most of us need a useful bandwidth across at least one full amateur HF band, and often across multiple allocations:

• Multi-band HF stations
• ALE and frequency-agile systems
• Multi-channel, tunable HF radios

Thicker elements have a lower Q factor, which translates into a wider usable SWR bandwidth. In practice, a thick HF radiator:

• Makes matching easier across an entire band
• Is less sensitive to detuning from nearby structures, rain, and ice
• Stays usable even when the environment isn’t “textbook perfect”

Thin, multi-section whips tend to be narrow-band and fussy, especially on the lowest HF frequencies. A few kHz of drift from weather or mounting changes can pull them out of the sweet spot much more easily.

Power Handling And Voltage Stress On HF

HF antennas see significant RF voltages, especially toward the ends of the radiator and in loaded or matched designs. This is even more critical when you combine:

• Higher transmit power levels
• Long duty cycles (FT8, RTTY, AM, digital voice)
• Matching networks and loading coils that concentrate voltage

With a thick, solid radiator:

• The conductor runs cooler for a given power level
• The mechanical and thermal margins are higher
• There is much less risk of local heating or arcing at threads or thin sections

Multi-piece thin whips place a lot of electrical stress on:

• Small threaded connections
• Sliding or plug-in sections
• Contact faces that gradually oxidize and pit under RF current

For serious HF work, a heavy-duty, continuous radiator is simply more trustworthy and repeatable over years of operation.

Mechanical Reliability Of Long HF Elements

HF elements are long, which means:

• Higher wind load and bending moments
• More vibration and fatigue over time
• Greater risk of damage from storms or ice

A 30 mm diameter, 2 mm wall aluminium tube provides:

• High stiffness, so the antenna whips and bends less in the wind
• High strength, improving survival in bad weather
• Sufficient wall thickness to resist dents and thread damage

Every extra joint in a slim multi-piece HF whip is:

• A mechanical weak point that can loosen or crack
• A place where water and dirt can collect
• A fatigue hotspot that slowly degrades with wind and movement

Fewer pieces means fewer failure points, both electrically and mechanically.

Why We Don’t Use Small Multi-Piece Poles On HF

Yes, thinner, multi-section HF antennas are tempting because they are:

• Cheaper to ship
• Easier to pack and store
• Lighter to carry temporarily

But on HF, that convenience comes with real trade-offs:

• Lower radiation efficiency, especially on the low bands
• Narrower SWR bandwidth and more frequent retuning
• Performance that drifts with weather, corrosion and movement
• More mechanical failures and maintenance over the life of the antenna

Our 30 mm diameter, 2 mm thick, one- or two-piece aluminium radiators are chosen specifically for HF because they deliver:

• Higher efficiency on electrically short HF bands
• Wider, more forgiving bandwidth
• Stable tuning in real-world, non-ideal environments
• Long-term mechanical reliability that matches the electrical performance

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