Aziloop DF-72 Stepped-Azimuth™ Directional RX Loop

Why Aziloop matters on the low bands

On 160m, 80m and 40m—especially in suburban environments—receive performance is often limited by QRN/QRM and local noise sources, not transmitter power. The DF-72 is built to help you improve signal-to-noise ratio by changing the receive direction and pattern quickly, letting you suppress interference rather than trying to brute force your way through it.

• Fast electronic steering to peak desired signals and null unwanted QRM.
• 108 directional combinations (72 K9AY headings + 36 loop axes) and rapid switching (about 60 ms).
• Receiver-friendly control: switchable preamp, attenuation, and preselection filters to keep front ends happy.

Video: Aziloop @ DL8LAS 1557 kHz (directional steering / nulling demo).

What is Stepped-Azimuth™?

Stepped-Azimuth™ is QuietRadio’s approach to “rotating” direction electronically. The loops don’t move—Aziloop processes the loop signals to synthesize headings in 5-degree steps, producing up to 72 unidirectional headings in K9AY mode and 36 bidirectional headings in Loop mode (108 total heading/mode combinations).

SWLing Post contributor Dale Parfitt highlights why this matters in practice: the rear null can be extremely sharp—so the ability to step through headings in 5-degree increments makes those nulls visible and usable. He reports achieving up to ~30 dB front-to-back in K9AY mode at his QTH.

Two modes: Loop and K9AY

Loop mode (classic small-loop behavior)

In Loop mode, Aziloop behaves like a small receive loop: a figure-of-eight pattern at low angles and more omnidirectional behavior at higher angles. This can be very effective for rotating null axes to reduce interference and noise.

K9AY mode (terminated loop cardioid for low-angle DX)

In K9AY mode, the system operates as a terminated loop producing a low-angle cardioid response with a rear null—a classic approach for low-band DX reception.

Why adjustable termination is a big deal

A key advantage of the DF-72 is the ability to adjust the K9AY terminating load electronically from 250 Ω to 950 Ω in 50 Ω steps.

The best value depends on your loop size, ground, and local surroundings—and on the day/night balance of groundwave vs. skywave. Changing R reshapes the cardioid pattern, often improving front-to-back, and can shift the null up or down in elevation to better attenuate signals arriving at different angles.

Video: MPPT solar charger noise on 80m (noise nulling demo).

Usable bands for hams and SWLs

Ham radio operators (receive)

• Low-band DXing (160m/80m): Improve readability by nulling local noise and regional interference (including over-the-horizon radar, OTHR).
• Contesting & DX: Rapidly peak a weak caller or multiplier and null loud regional stations—without changing your transmit antenna.
• Workflow advantage: Effortless direction control via API. Integrates with N1MM, DXLog, and other loggers able to send azimuth via UDP.

SWL & DX listening (receive)

• LW/MW: Fast null steering for MW DXing and utility/NDB-style listening.
• HF broadcast bands (e.g., 49m): Selective nulling can help separate co-channel or adjacent-channel stations in crowded shortwave broadcast segments.

Note: Overall coverage and directivity depend on your loop size and installation. Aziloop is designed for a primary range of 20 kHz to 10 MHz with coverage to 30 MHz at reduced directivity/sensitivity, ultimately determined by antenna size.

Loop size options from the manual: Standard / Medium / Full K9AY

As noted in the manual in the Downloads tab on the PileupDX product page, QuietRadio provides three practical build paths: Standard (smallest and suitable for 40m), Medium, and Full K9AY size (largest). The big-picture tradeoff is simple: larger loops generally deliver more low-band output, while smaller loops tend to preserve better behavior at higher frequencies.

QuietRadio’s user guide gives a helpful rule of thumb for untuned broadband loops: keep the loop circumference under ~0.1 λ at the highest frequency of interest. It also notes you can go smaller (generally fine) with reduced output proportional to loop area.

How to choose quickly

• Choose Standard if 40m DX/contest receiving is a priority and you want a compact, flexible build.
• Choose Medium if you primarily care about 160m/80m and MW/49m, and you can spare more footprint.
• Choose Full K9AY if you have room and want maximum low-band emphasis—especially at quieter sites.

What’s delivered (and what you supply)

In the box you get the Aziloop DF-72 electronics and connection accessories: the DF-X Common Interface Unit (CIU), the DF-72 Loop Control Unit (LCU), a DC power lead, a USB cable, a 3.5 mm to phone AUX cable, and two SMA-to-BNC adapters.

Because of the user selectable antenna configurations, you supply the antenna wire elements and the support/mounting hardware separately to build the desired loop type.

What other operators and listeners say

SWLing Post: “the rear null is very sharp”

In a field report published by SWLing Post, contributor Dale Parfitt calls out the standout feature as the ability to rotate electrically every 5 degrees and run two modes (Loop and K9AY). He reports that in K9AY mode he can achieve up to ~30 dB front-to-back and emphasizes that without 5-degree increments you might not even “see” the nulls well enough to use them.

Why low-band DXers like the K9AY family

QuietRadio’s DF-72 user guide describes the K9AY as a “renowned” DX receive antenna, explaining that its DX capability comes from a low-angle cardioid main lobe (with directivity eventually deteriorating above the antenna’s in-spec limit as size/frequency tradeoffs come into play).

The AziLoop DF-72 is used by top contest stations like KS7V, VP2M and SZ1A and on DXpeditions as 3C2MD, 9L9MD and J51A.