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CTX 3030 Threshold blanking

October 25, 2012 10:50am

Gordon Heritage
Gordon Heritage metal detector professional

One of the best things about FBS and FBS 2 detectors is their superior discrimination. Not only can you discriminate targets on their conductivity, you can also discriminate by their ferrous content simultaneously.

One of the things I’ve recently been reading on a few forums, are comments stating the new CTX 3030 has “still got the nulling problems of the E-TRAC”. I agree the ability to null, or blank the audio as Minelab refer to it, is still in the new detector… however, this is a feature not a problem.

CTX Blanking

So why does the CTX 3030 blank? It does this because the discrimination has been set to eliminate certain junk targets. When one of these targets is detected, instead of hearing it, the Threshold is blanked.

When using the E-TRAC I found the recovery-rate from a blank to a new target was quite long, so I used discrimination sparingly. I would rather alter the iron responses so I could identify them, than completely eliminate (blank) the signal.


The resulting extra stability has allowed me to pick out targets missed on previous hunts.

The second cause of blanking occurs when you are searching bad ground with extremely variable mineralization. Because the CTX 3030 is very sensitive, it detects these anomalies as discriminated targets (which they are) and eliminates them. There are ways of reducing these blank, like switching to auto-sensitivity, but I prefer to just slow down my sweep speed. The blanks become my gauge to the ground conditions and how fast I should be detecting.

It is possible to remove all blanks, or should I say; add back all the noise!

There are many ways of using the CTX 3030, and with features like the “Combined” Tone ID profile, it’s possible to construct a program based on audio discrimination. To do this just remove any pattern (searching with screen wide open) and listen for the good targets breaking through the noise. A lot of users were doing this using the E-TRAC, on sites where tiny low conductive coins could be heard giving low tones in a medley of high pitched squealing.

The added control over all audio parameters of the CTX 3030, has made this method even more viable.

So to recap;

  1. Blanking is a feature of the CTX 3030’s excellent discrimination capabilities, NOT a problem.
  2. Blanking can be your guide to how bad the soil is on the field you’re searching.
  3. The more you discriminate, the more you blank.

Now get out there and find something!

Gordon Heritage



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