NECtacy in the Park

A technical critique of the “POTA PERformer (Portable, Elevated, Resonant) Antenna” by KJ6ER ... and why the published numbers collapse without reality checks.

(This is not a critique of building portable verticals. Elevated tuned radials can work very well. This is about treating a single tidy model run as deployable truth.)

What the document claims

The PDF presents the PERformer as a one-band-at-a-time elevated quarter-wave vertical (40–6 m) with the feedpoint roughly 4–5 ft above ground and two tuned elevated linked radials placed 90° apart. It anchors “performance advantage” in 4NEC2 outputs and asks the reader to treat those numbers as actionable.

The core claims it leans on include:

• “Over 90% efficient” in the field, contrasted with a “typical” ground-mounted quarter-wave with four ground radials being “only 37% efficient.”
• Two elevated radials at 90° provide “modest gain (0.3–0.5 dBi)” and “3–4 dB front-to-back” “within the 90° span.”
• A highlighted 15 m example (~21.35 MHz): about +0.31 dBi max gain at ~24° elevation, F/B ~3.37 dB, and an extremely low reflection coefficient (return-loss style number).
• A follow-on table implying switching from 180° radial span (more omni) to 90° span yields up to several dB “more forward gain” at selected elevation angles.
• “You’ll never need a tuner,” and even at 1.5:1 SWR your “power throughput efficiency is 96%.”

None of these are inherently impossible as model outputs. The issue is the epistemology: the PDF treats those figures as if they survive contact with real portable conditions (soil variability, slope, clutter, coax routing, operator proximity, and choke effectiveness) ... exactly the environment a park antenna lives in.

The core failure mode: NEC as oracle instead of tool

This is textbook “NECtacy”: simulation outputs become scripture, and missing assumptions get treated as irrelevant. NEC is an excellent comparative tool under stated assumptions. It is not a guarantee generator for field setups that change every deployment.

“Over 90% efficient” is presented like an absolute

The PDF uses an “efficiency” number as if it represents real-world system efficiency for a portable installation. In practice, there are multiple efficiencies:

• Radiation efficiency of the structure (what a model can estimate under a chosen ground model and conductor assumptions).
• System efficiency, which also includes loading/matching losses, choke/common-mode behavior, connector/contact losses, and the environment coupling that portable antennas are famous for.

A key problem is internal contradiction: the document itself acknowledges that soil and near-field surroundings vary by deployment and that feedline common-mode can distort patterns if choking is not solid ... and then it sells specific efficiency and dB claims as if they are stable.

Match porn: return loss and “96% throughput” are not performance proofs

Highlighting extreme return loss (or a dramatic SWR dip) is not proof of “high performance.” A good match can coexist with poor far-field radiation if power is being dissipated in loss resistance (ground loss, coil loss, common-mode loss, etc.).

The polar plot is treated like a universal fact

The document anchors directionality in a single modeled case (15 m around 21.35 MHz) and then extrapolates into operational advice ... “choose compass headings for extra gain” ... implying repeatability.

But far-field pattern for a low portable vertical depends heavily on:

• Ground parameters (conductivity and permittivity)
• Ground geometry (flat vs slope vs edge effects)
• Height above ground in wavelengths (which changes every band)
• Nearby conductors (tripod, stakes, fence wire, picnic table, your body)
• Feedline routing and common-mode current

If you want to publish “+0.98 dB forward gain at 24°” as operationally meaningful, you must state the model inputs that control that answer ... ground model/parameters, wire radii/material, segmentation, kernel choice, and whether the feedline/choke were modeled. Outputs alone are not reproducible.

F/B ratio is being smuggled in as “gain”

The PDF blends front-to-back (F/B) and directional skew into a “gain” narrative. The clean relationship is:

When someone claims “gain” from asymmetry (like altering radial geometry), what’s often happening is redistribution of radiation and/or uncontrolled extra radiators (feedline common-mode, mast coupling, operator coupling). The PDF itself warns that without a proper choke, patterns become inconsistent ... which is exactly why precise dB claims are fragile.

The “gain delta” table is the clearest NECtacy moment

A table of single-run delta values at selected elevation angles reads like a numbers brochure ... not engineering. In portable HF, 1 dB can be inside the variability envelope of soil moisture, setup height error, radial sag, nearby objects, and feedline routing. If the numbers do not come with sensitivity analysis (or error bars), they’re decoration.

“Resonant antennas are always best and most efficient” is simply false

The document leans on a common slogan: resonant = efficient, and “no tuner” = “no losses.” That’s not how efficiency works.

• A resonant antenna can still be very lossy (especially if it’s strongly loaded).
• A non-resonant antenna with a low-loss matching network can be extremely efficient.
• “No tuner” is not automatically “more ERP.”

If you want to claim one approach is more efficient, you must quantify the actual loss mechanisms involved ... not just point at resonance or SWR.

Reproducibility is missing

If you publish performance numbers (efficiency, gain, F/B) as stable and meaningful, you need to provide the ingredients:

• The NEC model file(s) or full geometry listing
• Ground model and σ/εr
• Wire radii/material assumptions
• Segmentation and convergence checks
• Kernel choice
• Whether feedline/choke were modeled (and how)

Without that, readers cannot verify anything. That’s the definition of “numbers without backing.”

The concept is fine ... the certainty is broken

Elevated tuned radials can absolutely reduce near-field ground loss compared to a weak ground radial field. They can be a very practical portable solution. The critique is not “this can’t work.” The critique is “stop publishing single-number claims as if they’re universal.”

If directionality is the goal, asymmetry can increase skew/RDF

If you deliberately break symmetry (one radial, lopsided return, compact asymmetry), you can increase pattern skew and potentially improve receive SNR in some noise environments (RDF logic). On transmit, it’s usually redistribution ... and it may be paid for in efficiency or stability unless the system is rigorously choked and repeatable.

What a scientifically solid version of this PDF would include

• Model disclosure: publish the NEC files and state ground parameters.
• Sensitivity analysis: show how “forward gain deltas” change across plausible soil, height, and routing variations.
• Validation: controlled A/B experiments (rotation, repeated cycles), reporting distributions ... not single numbers.

Bottom line

The PERformer PDF doesn’t fail because it uses NEC. It fails because it treats NEC outputs as authoritative truth while:

• not disclosing model assumptions,
• not enabling reproducibility,
• not validating gain/efficiency claims with controlled measurements,
• and simultaneously acknowledging that soil and common-mode currents can change the system.

NEC is a fantastic comparative tool. But when a portable antenna document publishes single-number dB deltas and “efficiency” claims without error bars, ground parameters, or measurement backing, it stops being engineering.

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