RF Guru

OctaLoop a shielded active H-field Loop antenna 1MHz – 30 MHz

Name: OctaLoop a shielded active H-field Loop antenna 1MHz – 30 MHz
Brand: RF Guru
SKU: 2024-RX-855
Price: 258.0 EUR
Availability: InStock

€258,00 EUR

~~€189,00 EUR~~ €258,00 EUR

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Extra Coaxial Cable (10m standard included!) No Extra Coaxial Cable 10 M Coax Cable 75 Ohms 20 M Coax Cable 75 Ohms 40 M Coax Cable 75 Ohms 60 M Coax Cable 75 Ohms 100 M Coax Cable 75 Ohms

RVS Ground Peg with RX Line Isolator No RVS Ground Peg RVS Ground Peg (incl. F connector) with RX Line Isolator

Product variants

Quantity

Listen here (-2m ASL Lombardsijde Belgium): OctaLoop SDR

Included:

OctaLoop Antenna (3.65m circumference)
Stainless Steel (RVS316) Mounting Bracket
Bias-T 13.8V F-Type to SMA
Short SMA to BNC Cable
10M INTSAT-170-ELITE 75Ω coax cable with 2 F-Type Connectors

Optional:

RVS Ground Peg (including F connector bulkhead) and RX RF Line Isolator

Product Description: The OctaLoop is a high-performance HF active shielded H-field magnetic loop antenna, engineered for exceptional low-noise signal reception. Designed for both urban and remote environments, it significantly reduces EMI and improves signal clarity.

Compact, highly sensitive, and optimized for HF monitoring, the OctaLoop is an ideal solution for shortwave listening (SWL), amateur radio DXing, and SDR applications. Its shielded magnetic loop design and build in common mode rejection, ensures superior rejection of local interference, allowing for clearer, more stable reception across the HF band.

With an impressive IP3 of +45 dBm due to a push-pull design, the OctaLoop delivers outstanding dynamic range and signal fidelity. Covering 500 kHz – 50 MHz, but optimized for HF 2MHz – 10 MHz, it is a versatile and reliable choice for serious radio enthusiasts and professional monitoring applications.

Placement Recommendations: For optimal performance, install the OctaLoop at a location well away from buildings, power lines, and other sources of electromagnetic interference (EMI). The antenna operates most effectively at a height of 1.2 to 5 metres, providing a balance between noise reduction and signal reception.

If the feedline to the loop is longer than 10 metres, you can install a CMR choke midway along the feedline to minimise noise.

Grounding: For improved performance, grounding the braid of the coaxial cable feedline to a proper earth ground is highly recommended. Avoid grounding the coaxial cable to the mast itself—grounding should be performed at the base of the mast instead.

Test It Yourself!
Experience the OctaLoop’s performance in real-time by tuning into one of our SDR receivers: https://rf.guru/sdr

Do you need a rotor ? Understanding the Null of a Shielded Active H-Field Loop Antenna

Why an Octaloop is Superior to a Square or Circular Loop Antenna

Deep Nulls and Their Use in Noise Rejection

One of the most significant advantages of the OctaLoop is its sharp nulling capability. Unlike omnidirectional antennas, a magnetic loop exhibits a well-defined directional pattern.

The deep nulls are present at the sides of the loop (broadside to the loop plane), making it highly effective at rejecting noise sources coming from specific directions.
This deep nulling effect is particularly beneficial in rejecting local interference from nearby power lines, electric fences, and household appliances, where an operator can rotate the antenna to null out unwanted signals.
The depth of the null is frequency-dependent, being most pronounced in the MW and lower HF bands.

Polarization and Take-Off Angle

Unlike vertical or horizontal wire antennas, the OctaLoop primarily receives magnetic field (H-field) components rather than the electrical field (E-field). This has several advantages:

Lower susceptibility to local noise, as most electrical interference is in the E-field domain.
Polarization: The received signal is predominantly magnetically coupled, which means it is less affected by multipath interference.
Take-off angle: The antenna pattern is typically low-angle at lower frequencies, making it ideal for groundwave and DX reception. However, its reception pattern can be influenced by its mounting height and surrounding environment.

Handling Different Signal Types

The OctaLoop can effectively receive:

AM broadcast signals (MW band) with exceptional clarity due to its noise rejection capabilities.
CW (Morse Code) and SSB transmissions, where signal-to-noise ratio is critical.
Weak DX signals, especially in low bands such as 160m, 80m, and 40m.
Utility signals, including NAVTEX and time signals.
Propagation beacons, which are useful for assessing band conditions.

Ideal Use Cases and Placement

For best results, the OctaLoop should be placed away from large metal structures and rotated to optimize nulling against interference sources. It is well-suited for both indoor and outdoor use, with options for mast mounting or temporary setups for field operations.

Frequency Range and Performance Expectations

The OctaLoop is well-suited for reception across the low-frequency (LF), medium-wave (MW), and lower high-frequency (HF) bands, offering different levels of efficiency depending on the frequency range:

Frequency Range	Performance Expectation
500 kHz – 2 MHz	Very Good for MW broadcast stations, NAVTEX, and maritime communications
2 MHz – 10 MHz	Excellent for HF amateur bands (160m, 80m, 40m) and shortwave listening (SWL)
10 MHz – 30 MHz	Effective, but efficiency may drop, reducing deep nulling performance

Performance Considerations by Band

Mid HF (2 MHz – 10 MHz)

Peak performance range for this loop size.
Covers 160m, 80m, and 40m amateur bands, providing strong reception and good noise suppression.
Highly directional with deep nulls, making it effective for reducing local QRM.
Ideal for SWL, utility signal reception, and maritime/aviation communications.

Upper HF (10 MHz – 30 MHz)

Efficiency gradually decreases as frequency increases.
Deep nulling is less effective, but still useful for minimizing man-made noise.
Suitable for shortwave broadcasting, utility stations, and high-frequency amateur bands (20m, 15m, 10m).
Can still receive signals, but may not provide the same level of selectivity and noise rejection as at lower frequencies.