Gain and Sensitivity

Intro: 

Hey Everybody. Welcome! To Episode 57 of the metal detecting show podcast. My Name is Ciaran and I have been Metal Detecting for nearly 30 Years. This week I want to discuss some new terminology that has probably been around for years but I only discovered this week and that is Gain and how it relates to sensitivity.

Music

Hey everyone before we start I want to thank you for listening to the podcast and I hope you enjoy the episode this week  If you want to support the show there are many options available from the links in the episode notes below and if you want to interact with me and the show that information is there too.  

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Content:

Hey Everyone Thanks for listening to this week’s Episode before we Start I want to let you know that the giveaway draw is now closed. We have had a whopping 3500 entries for the equinox 600 plus some goodies so what happens next ciaran well entries will be reviewed for fraud and validity by kingsumo and they will then on my request randomly draw a winner to the draw tomorrow at 3pm both the winner and I will receive notification of the win at the same time and from there I will reach out to the winner to arrange shipping address and some other details. Why don’t I announce the winner straight away well as with anything the winner will have a few days to respond but in the unlikely event that they do not respond Kingsumo will do another draw mid week and this process will continue till we have a successful contact. 

So keep and eye out for a mail from KingSumo make sure to check your spam folder and unfortunitly if you havnt heard from us during the week you will have to hear with envy who has won this amazing prize.

So this week I went down to the thimble beach and got down to some serious hunting with my goto setup these weeks of the CTX and a 6’ coil on that I am soon to purchase a coiltek 6 inch coil for the equinox which I will review of course once I can find someone who has it in stock.

Anyways back to my hunt this week hit the beach and had some good finds but the standard beach toast but after about three hours the tide turned and holes became very difficult to navigate as they kept filling full of Sea water at this point I decided to park the detector and did another 30 mins of eyes only mudlarking finding a early 1900’s bovil bottle and an aqua marine glass stopper from the early 1800’s needless to say I was delighted and bounched home with my booty. 

Right this week I want to discuss Gain now if your like me this term may be new to you as it was new to me as this week I was trying to come up a new topic to discuss on the podcast and I was thinking I would do something on the Equinox Iron Bias evolution and Settings I kept coming across this term Gain time and time again it would come up and in frustration I  actually decided to research what the crazies were talking about and I spent some time googling now I do have an understanding of gain from an electronics point of view where gain  is defined as a measure of the ability of a two-port circuit (often an amplifier) to increase the power or amplitude of a signal from the input to the output port[1][2][3][4] by adding energy converted from some power supply to the signal. It is usually defined as the mean ratio of the signal amplitude or power at the output port to the amplitude or power at the input port.[1] It is often expressed using the logarithmic decibel (dB) units ("dB gain").[4] A gain greater than one (greater than zero dB), that is amplification, is the defining property of an active component or circuit, while a passive circuit will have a gain of less than one.[4]

 Ripped that definition straight off of Wikipedia. 

But I could only find one reference from any detector manufacture, minelab and it was like the rosetta stone it all became clear. The minelab treasure talk refers to Gain as a function that allows the metal detector to be optimised for differing conditions; controlling the sensitivity of the detector to its environment and targets. 

So there it is Gain is Sensitivity now as I said I wasn’t totally ignorant to what gain is I use it every time I record a podcast I set my microphone gain to an appropriate level ensuring that you guys can hear me while maintaining the audio quality of the recording but what if I could use the gain on my microphone to demonstrate the effect of high gain or high sensitivity on your detector I always wanted to do some demos on the podcast but couldn’t see myself waving my detector about in my little studio here but I think this is a great opportunity so that’s what im going to attempt this week. I have devised the following plan I will play these three sound [bing,bong,booo]  as you can hear each sound is clear but only varies in volume from low to medium to high the volume of each sound translates size of the object detected so low equals a small object to high volume equalling a large object. Now to simulate gain on your detector im going to adjust the gain on my microphone with low gain equaling a low sensitivity setting to a high gain equalling a high sensitivity setting. What should be clear is that the lowering the gain will result ina point where the lower volume tone will not be pick up on the mic and conversely the higher the gain will result in the lower tones becoming clearer but sacrificing the signal quality at the higher volumes or larger targets in your detector. 

so lets test this theory.

Starting with the three tones again [bing,bong,booo] remember my soundboard volume is constant with the distance to the microphone being constant also.

So setting my microphone gain to low I will play the three sounds tell me which ones you can hear [bing,bong,booo]  did you hear any probably heard tones 2 and 3 with tone 1 being to low to be picked up by the microphone gain. If listening in the Car you might not hear any and you may need your headphones.

So next step setting my microphone to mid gain I will play the three sounds again tell me which ones you can hear now. [bing,bong,booo]   you probably hear all of them ok maybe a little low.

Now for the final step I’m going to set my microphone gain to the max gain. I will play the sounds again tell me which ones you can hear now [bing,bong,booo]  you probably heard them all but did you notice that the sound quality dropped as we had some clipping of as the gain pushed the audio samples above the recording threshold of my set up hear. 

So what does this mean Ciaran what has any of this to do with metal detecting or gain or sensitivity.

So in this demo we can see if you set you gain or sensitivity to low you will miss the smaller targets at a certain depth but if you set your gain sensitivity to high you will pick up everything and your detector will struggle to pick out the good target as the quality of the signal has degraded even though it is of high gain. So although you are increasing the sensitivity or gain you are also increasing the effect the EMI or electromagnetic interference has on the signal quality as in it degrades it greatly.

So believe it or not most detector have gain set to a certain range and when you adjust your sensitivity you are adjusting the sensitivity or gain within that range.

If you were to put gain on a scale of 1 to 10 your detector is most likely set to 6 as a factory preset as signal would degrade once you go above 7 and despite what you think all metal detector manufacturers want you to be successful and set this optimally maybe hopefully possibly. As I say with any of these deep dive this is my view of what i believe is happening based on a few hours of research but if you know for sure hit me up I would love to have some definitive on any of these topic.

Before we wrap up for the week if you have a topic you want me to cover please let me know a significant amount of time goes in each week to digging up a topic for the show so spread the love guys let me know what you want to discuss or want me to get to the bottom off 

Wrap Up 

That’s it for this week’s I hope you liked this episode of the metal detecting show podcast.

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Once again, I hope you have enjoyed this episode and we will chat to you all again next week. 

Get out there eyes down and Happy Hunting.