Pre-Amp In The Coil. Unique To The Sovereign/Excal Only

[Critterhunter]

Here's what Minelab says about the pre amp that is found in all Sovereign coils. These pre-amps are even in the aftermarket coils in order to work properly.

In-Coil Signal Booster

RCB (Receive Coil Boost) circuitry greatly amplifies weak target signals, from small and deep targets, inside the search coil, where the signals are received. This has three main advantages over standard techniques of amplification inside the control box:

1.Greater immunity to electrical noise, reducing false signals
2.No loss of signal strength, and faint targets, through the cable
3.Improved detection depth and sensitivity

(END OF REPOST)

Even the Explorer/Etrac doesn't have this in coil signal booster. One of the advantages of this technology is that it boosts the weak RX coil signal at the source before it has a chance to pick up any distortion traveling up the coil cable from outside sources. Inside the control box your sensitivity control then acts as a second amp, increasing the gain on the signal it's receiving. Some people think the sensitivity control increases the power of the TX signal being transmitted into the ground. It doesn't. That signal stays the same strength all the time. With the sensitivity control, what limits how high you can set it is how much distortion or white noise you are picking up. Even glare from the ground matrix can effect how much gain you can use. That's why in really bad ground you have to run at lower sensitivity settings.

 

[Critterhunter]

Here's another little blurb about it from Minelab...

In-Coil Signal Booster

Weak target signals are amplified inside the coil, before the receive signal is sent up the coil cable where interference and signal loss can occur. This technique improves immunity to electrical noise by reducing false signals and increasing target signal strength, therefore improving detection depth and sensitivity.

 

[Ism]

They derrive the power for the coil pre-amp from the transmit signal.
I don't think the output power is ever controlled on commercial detectors. It would change the rules for the receive circuitry and coil balance.

 

[Critterhunter]

I thought some of the higher end Whites have the ability to change the TX transmit power?

 

[Critterhunter]

One thing I have heard is some claim using a meter on the Sovereign that is powered by it's own battery will give the TX coil a little more power, since the meter isn't feeding off it. I think I saw one meter maker say something like "serious Sovereign hunters don't use a meter that derives it's power from the detector to insure maximum TX signal strength", or words to that effect. I wonder how much the DigiSearch meter really does lesson the size and strength of the TX signal?

 

[therover]

If memory serves me correctly, on the DFX the Pre-amp gain is for one power adjustment ( ie, TX transmit ), and the A.C. sensitivity for the other ( receive ). Could be vice versa.

Not sure what the naming convention is on the V3i, but I would imagine it has the same functionality.

 

[deepdiger60]

For those of you who are MD geeks that have not seen this yet , i read this 3 times and it,s starting to make sence , Bruce Candy wrote this for Minelab Jim
http://www.minelab.com/__files/f/11043/METAL%20DETECTOR%20BASICS%20AND%20THEORY.pdf

 

[Neil]

For those of you who are MD geeks that have not seen this yet , i read this 3 times and it,s starting to make sence , Bruce Candy wrote this for Minelab Jim
http://www.minelab.com/__files/f/11043/METAL%20DETECTOR%20BASICS%20AND%20THEORY.pdf

Excellent Jim, glad you found this as its from the designer of the Sov and Explorer series.

When you get to the end of it, the last line or two, he says that iron mask is ferrous discrimination"the ferrous signal is strong during these periods, the capability of ferrous discrimination is signifi cantly improved. This

 

[Ism]

One thing I have heard is some claim using a meter on the Sovereign that is powered by it's own battery will give the TX coil a little more power, since the meter isn't feeding off it. I think I saw one meter maker say something like "serious Sovereign hunters don't use a meter that derives it's power from the detector to insure maximum TX signal strength", or words to that effect. I wonder how much the DigiSearch meter really does lesson the size and strength of the TX signal?

It does make sense that the added load would increase current draw and reduce the output signal. This would have the effect of draining the battery faster and heating the finals if they were undersized. If the drain was more than could be supplied, then there will be a power loss to the transmit signal). But Minelab designed the Sov with the meter in mind so they would have taken the loss into consideration. Minelab manual says there is no signal loss and I can agree with them because of their engineering forethought. No doubt there will be losses "for every action there is an equal but opposite reaction", but they will likely be nothing more than shorter battery life.

 

[Critterhunter]

I don't know why being able to change the transmit coil's power would have any kind of useful function, but then I also question many of the seemingly useless functions high end Whites are loaded with.

 

[Critterhunter]

I think I remember now where I read that about "serious Sovereign hunters not using a meter in order to insure maximum depth". It was one of the internal meter makers (there is a guy in the UK who sells an internal meter and it might have been him). The internal meter derives it's power from elsewhere instead of feeding off the transmit coil power output to the coil.

 

[deepdiger60]

I think I remember now where I read that about "serious Sovereign hunters not using a meter in order to insure maximum depth". It was one of the internal meter makers (there is a guy in the UK who sells an internal meter and it might have been him). The internal meter derives it's power from elsewhere instead of feeding off the transmit coil power output to the coil.

Critter this was the guy from the UK Jim
http://www.findmall.com/read.php?21,1145158

 

[Critterhunter]

That might have been where I saw it. He says...

"Another point to note is the the Sovereign meter manufactured by Minelab is powered by the transmit signal of the Sovereign itself and this means that the main reason most "professional" metal detectorists don't use a meter with the Sovereign, is that using a meter means LESS DEPTH (due to a load on the transmit signal). Our meter is powered from the main battery and has been Engineered to take less that 0.5mA (that's one HALF of one THOUSANDTH of an amp). This means that in one full battery charge, you lose less than 30 seconds of detecting time!"

What that means is even if you have an external meter, if it runs on it's own battery (some do) there is no risk of reducing the transmit signal strength due to the meter feeding it's power off the TX signal outputs of the coil cable. On the other hand, that's wired in parallel anyways on say the Digisearch meter...Which means the TX coil is still getting full voltage from the control box just like the Digisearch meter is. So I don't know that it would make any difference to the performance of the detector.