What makes this a quad-core choke?

Two dual-core sections in series doubling choking impedance and thermal capacity.

Can it replace two separate units?

Yes, for mid/high HF it matches the performance of two dual-core chokes in series.

What power levels can it handle?

PL-259: about 3 kW PEP / 1.5 kW CCS. Type-N: up to 5 kW ICAS.

Where should I install it?

Install at the amplifier output, station entry, or directly at the antenna feedpoint.

Are these values theoretical?

No — all values are load-tested using EMC-standard common-mode injection and sensing.

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RF Guru

5kW ICAS Quad Core High Bands 40–10 m QRO 1:1 Current Balun or Choke

€226,00 EUR

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Connector PL N 7/16 DIN 7/16 DIN + PL

Grounding terminal No ground connection Stainless steel M6 ground connection

Product variants

Quantity

Complementary: Stainless Steel (RVS / INOX 316) Mounting Kit available — use the large version for this choke.

All our products are handmade, and fulfilment times may vary depending on order volume. Please allow 2–3 weeks for completion and shipping.

This is the quad-core compact QRO version of our broadband choke series — designed for high-duty HF operation using four stacked 2.4″ toroids arranged as two dual-core sections in series. It offers outstanding high-frequency isolation, low insertion loss, and robust power handling for both amplifier outputs and antenna feedpoints. The choke is enclosed in a HV-coated polycarbonate housing with custom silicone gaskets and a decompression valve for long-term outdoor service. All data are measured under load — no simulations.

Purpose-Built for Heavy-Duty HF Service (40–10 m)

This quad-core configuration offers exceptional wideband suppression and generous thermal headroom. It is ideal at amplifier outputs, station entry points, or directly at the antenna feedpoint to maximize common-mode suppression across the 40–10 m spectrum.

Specifications

Core configuration: 4 × 2.4″ toroids (two dual stacks in series)
Power rating (PL-259): ≈ 3 kW PEP / 1.5 kW CCS continuous
Power rating (N-type): up to 5 kW ICAS under 50 Ω load (ICAS rating applies to N connector only)
Connectors: PL-259 / SO-239 / N-type (N recommended for high-duty use)
Enclosure: HV-coated polycarbonate, silicone gaskets, decompression valve
Reference @ 50 Ω: Vpk ≈ 700 V, Vrms ≈ 500 V, Ipk ≈ 14 A, Irms ≈ 10 A

Measured Performance (Quad-Core, Two Stacks in Series)

Measured per EMC-standard procedure with controlled common-mode current injection and precision sensing under load.

Band	Choking Impedance (Ω)	Impedance-Equivalent dB (from \|Zc\|)
40 m	4.85 kΩ	45.8 dB
30 m	14.21 kΩ	55.1 dB
20 m	16.63 kΩ	56.5 dB
17 m	6.39 kΩ	48.2 dB
15 m	4.51 kΩ	45.1 dB
12 m	3.35 kΩ	42.6 dB
10 m	2.73 kΩ	40.8 dB
Impedance-Equivalent (dB) values are computed directly from measured \|Z_CM\| using a 50 Ω common-mode source reference. Real antennas rarely present 50 Ω in common-mode, so these figures represent the choke’s intrinsic suppression capability*, not the attenuation of a real antenna system. More background: Why dB Attenuation Specs on Ham Chokes Are a Mess.

Practical Note — 40 m is Borderline for QRO (But Close Enough)

On 40 m this choke measures ≈ 4.85 kΩ of common-mode impedance. A common “QRO-safe” rule-of-thumb is ≥ 5 kΩ, so 40 m is borderline — but very close, and typically sufficient in well-behaved installations.

If you want extra margin for legal power (≈ 1.5 kW), add a second choke in series at the station (shack) entrance: either a wideband 160–10 m choke or another 40–10 m choke. This pushes the total common-mode impedance on 40 m comfortably above the 5 kΩ guideline in most real stations.

Series stacking tip: chokes in series add in Ω (Z_total ≈ Z₁ + Z₂). Do not add the dB figures. If you want an “impedance-equivalent dB” number, recompute it from the total |Zc| using the same reference as the table.

Excellent wideband suppression from 40 m through 10 m (with very strong performance at 30 m as well). For extended low-band coverage (160/80/60), combine this unit with a dedicated low-band choke in series at the feedpoint or station entry.

Maximum ICAS/CCS Power Ratings

Connector Type	160–40 m Band	40–10 m Band	6–2 m Band	Limiting Factor
PL-259 / UHF	≈ 2.7 kW ICAS	≈ 1.3 kW ICAS	≈ 0.6 kW ICAS	Connector
Type-N	≈ 10 kW ICAS	≈ 5 kW ICAS	≈ 2 kW ICAS	Coax
7/16 DIN	≈ 10 kW ICAS	≈ 5 kW ICAS	≈ 2 kW ICAS	Coax

Installation Guidance

Install at the amplifier output, station entry, or antenna feedpoint for maximum suppression.
Horizontal or vertical mounting — the enclosure is sealed and pressure-equalized.
All ratings reflect conservative real-world measurements under continuous carrier load.

Technical Validation — How We Measure It

At RF.Guru Lab, all baluns are evaluated using EMC-standard dual-probe common-mode testing. One probe injects controlled common-mode current into the device under test, while a second probe measures the resulting CM current at the output.

This method reveals the choke’s true Common-Mode Rejection (CMR) under load — not the differential-mode artifacts seen in simple S21 shield-to-shield VNA tests.

Typical VNA fixtures excite the feedline in differential mode, so they do not measure actual CM behaviour. Our EMC method measures real suppression performance under power, matching what happens in tuner-fed and PA-fed HF systems.

Mini-FAQ

Q: What makes this a “quad-core” choke?
— Two dual-core sections in series, doubling thermal overhead and total |Zc|.
Q: Can it replace two separate units?
— Yes. For mid/high HF it equals the performance of two dual-core chokes in series.
Q: What power levels?
— PL-259: ~3 kW PEP / 1.5 kW CCS. Type-N: up to 5 kW ICAS.
Q: Best installation point?
— Amplifier output, station entry, or antenna feedpoint.
Q: Are these values theoretical?
— No. All values are measured under load using EMC-standard common-mode probes.