VLF output signal

[Mark-VA]

Generally, would it be correct to say most detectors are transmitting maximum output to the coil allowed by the FCC?

I know some machines like the V3i, Deus allow adjustments, but ...

[pebe]

The FCC limits only go down to 300KHz, so it appears they do not to apply to VLF.

http://www.rfcafe.com/references/ele...e-exposure.htm

[Mark-VA]

Thanks, I didn't know that.
Some of the internet forums have a lot of very misleading information.

[Dave J.]

Regulatory limits usually don't come into play. It's primarily about battery life and fact that huge increases in power buy you only a little additional depth, which you usually can't use anyhow because of ground pickup, target masking, etc.

Good example is the T2/F75/F70 machines. Indisputably lots of hots, and they get about 40 hours of battery life on 4xAA's. We could have run 'em on just 2, and customers would still have been happy about battery life.

[Koala]

Manufactures throttle back detectors to meet regulation is an that old urban myth seem to surface every few years.

[Mark-VA]

Thanks for the real facts. Thanks to you too Dave. In fact the whole reason to ask the question was the fact that my recent upgraded F75 LTD can detect (very good audio) a small copper rivet, the size of the end of a pencil eraser, 7" in the ground (been buried for many years). With these settings, BP, sensitivity 0 (yes 0), disc 0 and with DSP on. I know I kind of cheated a little with a discrimination of 0. Amazing results.
I might add, my TDI will not detect the rivet at gain of 2. My Deus will not detect at a sensitivity setting of only 50 regardless of settings.
But I truly love all those machines, each have their place.

[ODM]

ICNIRP limits on electric and magnetic field for consumer/civilian use begin from static fields, eg. zero hertz

[pebe]

The FCC is concerned with maximum radiation levels. Static fields don't radiate!

[ODM]

Of course. That is why we have other bodies besides FCC. They don't regulate toasters for example. Sigh.

[pebe]

True, but they are irrelevant to the OP's question. He referred to "transmitting maximum output to the coil allowed by the FCC"

[ODM]

Why is it irrelevant to point out that there are other regulations which may apply?

[pebe]

I said they were irrelevant to the OP's question.
He was asking specifically about the FCC limits on radiation, not about the limits on static fields or toasters, nor about any other body's limits.

[Qiaozhi]

The ICNIRP publish guidelines concerning electric and magnetic fields. They do not impose any official limits, or regulations.
As a taxi driver in Cairo once said to me, when he ignored the red traffic lights ... "They're only a guide."

[Koala]

http://www.geotech1.com/forums/showt...t=limit+output

[Mark-VA]

Dave, so can I safely assume the final transmit power decision of the F75 was based on the best possible performance and battery life ratio?
If that is the case, the performance of the F75 LTD is at its peak. Complete new design and platform would be need to surpass this machine.
The only machine that can trump the F75 in bad ground is the Whites TDI.
I've used over 15 different VLF machines in the past 20+ years and can honestly proclaim the F75 LTD has and continues to outperform all others, in my area.
Amazing device to satisfy my hobby.

Regulatory limits usually don't come into play. It's primarily about battery life and fact that huge increases in power buy you only a little additional depth, which you usually can't use anyhow because of ground pickup, target masking, etc.

Good example is the T2/F75/F70 machines. Indisputably lots of hots, and they get about 40 hours of battery life on 4xAA's. We could have run 'em on just 2, and customers would still have been happy about battery life.