Quick Answer: A multi-frequency metal detector — like the Minelab Equinox 900 ($999) or Nokta Legend 2 ($999) — transmits several frequencies at once instead of one, so discrimination stays consistent whether you’re in mild park soil, mineralized relic ground, or wet salt sand. Single-frequency VLF machines (Garrett AT Pro, ACE 400) still find just as many targets in mild, uniform ground for a fraction of the price; multi-frequency earns its premium once the ground itself starts changing under your coil.
Frequency gets mentioned on almost every detector spec sheet, but it’s rarely explained: what does running “one frequency” versus “several at once” actually change in the field? This guide breaks down VLF single-frequency, simultaneous multi-frequency, and pulse induction (PI) in plain terms, then points to the machines in each category worth buying in 2026.
VLF, multi-frequency, and PI at a glance
| Technology | How it works | Best for | Weak point |
|---|---|---|---|
| Single-frequency VLF | Transmits one fixed frequency, tuned by the user or preset | Mild soil, parks, coin/jewelry hunting | Loses discrimination in mineralized or salt ground |
| Simultaneous multi-frequency | Transmits and processes several frequencies at once, blended in real time | Variable ground, relic sites, beach and salt water | Higher price, steeper learning curve |
| Pulse induction (PI) | Sends sharp pulses and reads the decay, largely ignoring ground mineral content | Gold prospecting, scuba diving, heavily mineralized black sand | Little to no discrimination — digs almost everything |
Why frequency matters at all
A detector’s coil sends an electromagnetic field into the ground and reads what comes back. Ground minerals and salt water both distort that return signal, and how badly depends on the frequency being used — low frequencies (5-10 kHz) shrug off mineralization but struggle on small, low-conductivity targets like gold; high frequencies (15 kHz+) find small gold and jewelry well but get noisier in hot ground. A single-frequency VLF machine has to pick one point on that trade-off and stay there for the whole hunt. Minelab’s Multi-IQ engine — used in the Equinox 900 — instead runs multiple frequencies simultaneously and blends the results, so the detector doesn’t need the ground to stay the same for its target ID to stay accurate. According to Minelab’s own technology documentation, this is the core reason Multi-IQ machines are marketed as usable across coin, relic, beach, and gold modes on a single machine rather than requiring a different detector per environment.
Minelab Equinox 900 — Best Multi-Frequency All-Rounder
- Runs multiple frequencies at once and blends them in real time — no manual frequency selection needed as ground changes.
- Dedicated Park, Field, Beach, and Gold modes tune that same multi-frequency engine per environment.
- IP68-rated to 5 m (16 ft), so the same multi-frequency performance carries into wet salt sand and shallow water.
Researching frequency specs before you buy? Try Kindle Unlimited free for 30 days — its detecting-technology library covers VLF and multi-frequency theory in more depth than most manufacturer manuals do.
When single-frequency VLF is the smarter buy
Multi-frequency isn’t automatically the right call. In mild, uniform soil — most inland parks, lawns, and school yards — a well-tuned single-frequency VLF machine finds essentially the same targets a multi-frequency machine would, without the extra cost or the deeper menu structure.
Garrett AT Pro — Best Single-Frequency VLF for Mixed Ground
- Fixed 15 kHz frequency with manual ground balance — strong on coins and small relics in mild-to-moderately mineralized soil.
- Full read on our Garrett AT Pro review for the complete spec breakdown.
- $549.99 — roughly half the price of the Equinox 900 or Legend 2, with a simpler menu to learn on.
A single-frequency machine also tends to be easier to learn on for a first detector — one frequency means one clear tone-to-target relationship instead of a blended signal to interpret. That’s part of why the Garrett ACE 400 and AT Pro both remain fixtures on our beginner’s guide even with multi-frequency machines available at similar or higher price points.
Multi-frequency vs. pulse induction: different jobs entirely
Multi-frequency VLF and pulse induction solve different problems and rarely compete for the same buyer. Multi-frequency keeps discrimination — telling good targets from junk — working across changing ground. Pulse induction gives up most discrimination in exchange for depth in the worst ground conditions: heavily mineralized black sand and salt water that would blind almost any VLF machine, single- or multi-frequency. That’s why serious gold prospectors and dive hunters reach for PI machines like the ones in our gold detecting guide, while general-purpose coin and relic hunters stay on VLF, multi-frequency or not.
Multi-frequency by the numbers
- Two frequency bands is the rough working range for VLF detection — low frequencies around 5-10 kHz for mineralized-ground performance, high frequencies of 15 kHz or more for small, low-conductivity targets like gold — a trade-off simultaneous multi-frequency is built to avoid making at all (Minelab technology documentation, 2026).
- 5 m (16 ft) is the whole-machine submersion rating Minelab specifies for the Equinox 900, meaning its multi-frequency performance carries directly into wet salt sand and shallow water hunting, not just dry land (Minelab, 2026).
The bottom line
Simultaneous multi-frequency detectors like the Minelab Equinox 900 and Nokta Legend 2 trade a higher price for ground that no longer has to cooperate — useful the moment you hunt mineralized relic sites, salt beaches, or any ground that changes across one outing. If you mostly hunt mild, consistent soil, a single-frequency VLF machine like the Garrett AT Pro finds the same targets for less money and a shorter learning curve. Planning to hunt salt water specifically? Our waterproof detector guide and beach detector guide both dig deeper into the multi-frequency and PI machines built for exactly that ground.