GPZ 7000: Threshold Vs Sensitivity Vs Volume Vs Volume Limit (with Discussion On Audio Smoothing, Coil Control, Range Of Motion And Manual Ground Balance)

[Gold Catcher]

10 minutes ago, afreakofnature said:

I have read them all, believe it or not.  It took a hell of a lot of time and I have read them more than once.  First when they were posted and then again doing all this research to make a complete GPZ manual.  As well as many others posts from this forum too.  It was a huge community effort to put all this out and then to take all that and for me to try to summarize it all up.  I will have most if not all of JP's posts in that PDF manual that I will eventually share.  This has been my winter time goal.  To become "completely" knowledgeable in ZVT and GPZ functions so when spring hits I can begin testing all of this and see what I might have missed because of my prior ignorance.

What a great motivation and attitude. The more you know about your detector the better you will use all available settings to your advantage! I find the GPZ to be an incredible versatile machine. Although each of us have their own to go settings, no settings are universally applicable for all situations. Knowing the underlying principles for each function and how they relate to each other will make you an expert. Alot of gold is waiting for you ? 

[Gold Hound]

2 hours ago, jasong said:

Sensitivity seems to be the thing that you and other new people I see posting in other threads not entirely undertstanding, but I think I can help you there.

Sensitivity is the amount of gain the RX circuitry applies to the signals which the RX coil lobes detect from the ground. These are not audio signals, these are electromagnetic signals. Sensitivity is controlled by an EM frequency amplifier while audio is controlled by an audio frequency amplifier. Two completely seperate things. Think of a radio and an antenna, very similar thing happening. An FM radio has both an FM frequency amplifier and an audio (volume) amplifier. Does turning up your volume do anything at all to a weak FM radio signal? No, because the audio amplifier is not amplifying the actual radio signal, it only amplifies the demodulated audio signal. So increasing the volume without increasing the FM amplifier gain will only amplify static noise (EMI) and not the radio station you are trying to hear (the nugget). To pick up more distant or weak radio signals (nuggets) you either need a better antenna (different coil) or a stronger radio frequency amplifier (more gain/sensitivity).

Sensitivity (aka Gain) determines how sensitive your machine is to weak signals. All the audio (volume) amplification in the world won't make a signal appear which the RX circuitry is not strong enough to amplify. More Sensitivity however will allow the detector (and thus the audio circuitry, and eventually your ear) to hear signals which it cannot hear at all at lower Sensitivities.

But! RX gain/sensitivity also amplifies any signal the coil is picking up, including EMI. Which is why people like myself use the audio controls to adjust for and control the amount of noise you hear. I always, always, always run as much Sensitivity as possible for the conditions, then use the audio controls to compensate for noise. When you read the manual, this is exactly why those controls exist, and how the GPZ appears to be designed to be used.

And this is why I have said since 2015 that it's better to run in as high of Sensitivity as you can, and then to tamp it all down and control the mess with the audio controls. Even in high EMI environments like we have often in the USA. Because running low gains means you are eliminating a ton of signals that will never be heard at all by the detector, and thus will never be heard by you no matter how much you fiddle with the volume controls. The speed and method you swing a coil can often be used to differentiate target signals from EMI too. The biggest mistake I see new detectorists make is running low gains then thinking they are compensating by boosting volume controls up and then thinking they are gaining something more by boosting audio even further with an audio booster. All the volume boosting in the world will not amplify a signal that isn't in the detector to begin with because you are running Sensitivity/Gain too low.

That said, my experience (and I recently met another very experienced individual who independently has the same experience) is that past a certain level of Sensitivity, you will tend to boost more EMI than target response. In my experience, this level is at 18 Sensitivity. Going to 19 and 20 seems to exponentially increase the EMI while only linearly increasing target response. That's why in noisier parts of the US I find 18 Sensitivity to be the sweet spot, and you will see since 2015 this is what I've posted here. I can run 20 gain with some benefit in quieter parts of the country.

Normal loves high sensitivities. When the ground thaws, do your own testing on test nuggets rather than taking my word for it. The difference between 18 Sensitivity and 10 Sensitivity is huge when it comes to a nugget you can just barely hear at 10 or just beyond 10's detection range, it will be a sweet target at 18 often. There is no ground, and no part of the USA which I have found any place necessary to run below 12 gain where you can't get better performance by instead running higher Sensitivity (wet salt ground being the only single exception I've encountered, but this varies) and using audio to process the RX boosted signal isntead. RX Sensitivity is the first thing you want to maximize because if it's too low then your detector will simply miss entirely a lot of deeper nuggets. 

I havent lowerd the sensitivity/gain below 20 for years?

I adjust my swing speed to compensate for ground noise and emi is just music to my ears. If you watch my mountain goat gold vid or any vid of me detecting youll hear how noisy I run my detetctor.

My philosopy is that since I own a ferrari Im going to drive a ferrari... and drive it HARD and push it to its limits and test mine ?

[Norvic]

11 minutes ago, Gold Hound said:

My philosopy is that since I own a ferrari Im going to drive a ferrari... and drive it HARD and push it to its limits and test mine

Love it, that Ferrari analogy is the go.

[Gold Catcher]

23 minutes ago, Gold Hound said:

My philosopy is that since I own a ferrari Im going to drive a ferrari.

I like Ferrari-gold. There might be different ways to get there however...;)

[Northeast]

4 hours ago, afreakofnature said:

I plan on posting this "revised" manual in the future for everyone to have.

Just check with Steve H and JP first.  I was going to do the same thing and in the end we decided it was not the best thing to do - copyright issues, etc.  Steve's site, JPs words, my manual - it just seemed messy  ?

[Northeast]

3 hours ago, jasong said:

JP has posted many times that Difficult is inherently high gain built into the timing. So results may be different there.

 

1 hour ago, afreakofnature said:

Noise Canceled.  Gold Mode: High Yield.  Ground Type: Normal.  Ground Balanced with Semi Auto.  No filters - Audio nor Ground Smoothing.

Yes, that might change things a bit.  95% of my detecting with the Z is in Difficult.  Varies between High Yield and General (more General).  Semi auto GB and no filters.   

But do plan on trying Normal more and bringing in the use of the audio filters as jasong has suggested.   

[afreakofnature]

2 hours ago, Northeast said:

 

Yes, that might change things a bit.  95% of my detecting with the Z is in Difficult.  Varies between High Yield and General (more General).  Semi auto GB and no filters.   

But do plan on trying Normal more and bringing in the use of the audio filters as jasong has suggested.   

Let discuss those options in a different thread.  Just so we can stay on topic with these controls.  Otherwise we will go in a completely different direction.  Actually alot of that has been discussed before but never the focus on these 4 specific controls.  Thanks Northeast!

[afreakofnature]

2 hours ago, Northeast said:

Just check with Steve H and JP first.  I was going to do the same thing and in the end we decided it was not the best thing to do - copyright issues, etc.  Steve's site, JPs words, my manual - it just seemed messy  ?

I'll put that in another thread later.  But I am not worried about it.  I am not charging any money for my research ?.  Or for that matter charging any money for the manual.  I will just be giving away my research for free that anyone else can download  or copy for free on the internet.  My name is not even going to be on it.  Plus everyone is referenced after their post with their DP name.  Think of it as a compilation.  Definitely not a publication.

[mn90403]

Do I get a credit for proof reading?