KNOWLEDGE BASE ARTICLE
MPF Technology

The SDC 2300 and MPF Technology Explained
Minelab’s SDC 2300 gold detector uses Multi Period Fast (MPF) Pulse Induction (PI) technology to give significant
performance improvements over conventional PI metal detectors, for gold prospecting in mineralised ground.
In this article, the inventor of MPF, Bruce Candy, explains further how the SDC 2300 works.

“You will find more small nuggets and fine-threaded specimen gold in mineralised soils withthe SDC 2300 than any other gold detector, including the GPX 5000.” –Bruce Candysignals when the coil is passed over highly magnetic soils, andmany gold fields have such soils. Conventional Pulse Induction
detectors typically produce a decaying transmit signal ofsignificant duration, and this limits the earliest possible receive
signal processing after the transmit signal begins to decay.
This is a major limitation for the detection of small gold, (e.g.
<0.1gram), because small gold (and specimen gold) signals
only exist for a very short duration after the transmit pulse
begins to decay.

Technology:
MPF incorporates extremely
fast Pulse Induction switching
Tx
Rx
between Transmit (Tx) andGold
Receive (Rx) detector signals.
Therefore minimal residualtransmit signal is present during the receive cycle, enabling
clear sharp detection of very small gold.

Thus with conventional pulse induction electronics, highsensitivity to small gold comes at the expense of extra
ground noise in highly magnetic soils.

The problem with conventional PI detectors
for small gold

The MPF technology solution for small gold

In pulse induction metal detectors, the transmit signal needs
to be completely ‘shut down’ before the tiny receive signals canbe processed and sent to the audio, especially if the same coilis being used to transmit and receive, such as a mono-loop coil.
If the transmit signal is still present when receive processingcommences, it in effect adds variable un-ground-balanced

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The electronics in the SDC 2300 produces a near instantaneoustransmit waveform switch-off. This innovation thus allows forreceive signal processing ASAP immediately after this rapid
termination of the transmit waveform, and hence MPF’s receive
processing allows for higher sensitive detection of small gold
without the associated extra soil signal in highly magnetic soils.
The graph below compares MPF to conventional PI.

Transmit signal following the commencement of pulse
induction transmit signal switch off. Conventional PI takes arelatively long time to reach near zero before receive signal
processing can begin, whereas the SDC2300 transmit signal
switches off rapidly and allows for earlier receive signal
processingMPF

KNOWLEDGE BASE ARTICLE | KBA 23-1

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What are the performance advantages?
Improved Sensitivity

Greatly Reduced EMI

To improve sensitivity to small targets, the transmit
frequency is about 3kHz, which is much faster than aconventional PI detector. This means more averaged
signal per second (3000 signals per second) of the
weak small gold signals. The faint metal target
signals are the same following each transmit pulse,whilst the electronic noise is random. This meansthat the noise averages to a low level compared to
the faint metal target signals , making the target
signal ‘stand out’ from the noise.

The SDC 2300 electronics has low EMI susceptibility,especially from mains-borne EMI, and sferics as well.

Reduced Ground NoiseThe SDC 2300 incorporates Minelab’s proven“Enhance/Fine Gold” type of receive processing thatminimises mineralised soil signals and false detectionof hot rocks, unlike traditional PI detectors. This
greatly assists with nugget detection in most goldfields, especially in highly mineralised gold fields.
This substantial reduction in ground noise makes
prospecting less confusing and more time efficient,
It incorporates Automatic Ground Tracking andFast Ground Balance so that the detector is always
optimally ground balanced.

Performance in Salty Conditions
The SDC 2300 incorporates a Salt Mode for which
the transmit and receive timing signals have been
optimised for saline conditions found in some gold
field areas.

Matched Coil
The ideal coil depends a lot on what targets you want
the best chance of finding. Small coils are particularly
sensitive to targets which are buried shallow, whilelarge coils maintain their sensitivity better at greater
depths but sacrifice sensitivity to shallow targets. The
MPF technology is tuned to find small gold nuggets.
These nuggets are typically found closer to the coilthan larger targets. To further enhance the ability of
the SDC 2300 in finding small gold nuggets we’ve
equipped it with an 8” mono‑loop coil, which isideally suited to finding the small gold at the depths
where it is predominantly found.

“The SDC’s unique advantage is ultra-low ground noise in mineralised and saline soils AND
very high sensitivity to fine gold and fine targets (like chains) at the beach.” –Bruce Candy

Where to find more information
The following patents that apply to the SDC 2300 provide further
insight into its featured innovations:
WO2011156870; Patent for the near instantaneous pulse
induction transmit waveform switch-off. This also allows forhigh power efficiency compared to normal pulse induction
and thus lower battery power consumption.
WO2013131133; Assists with the receive signal processing
ASAP immediately after the rapid termination of the transmit
waveform.

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