Lot of discussion of VCO but what is it?

[silysavg]

I used my new V3i yesterday for 3 hours. I really like it so far. I think I am going to love it - pretty sure. However, I need to get the pinpointing down to a better science.
Knowing that I watched the video again and read the Owner's Guide again.

The pinpointing nowadays is not as exact as it was in the 80's ( i have been on a MD'g hiatus ).
A swing left & right then back & forth and X marked the spot. It was quick. Real quick.

The V3i takes a bit longer to pinpoint and is usually off a bit - either forward or back of what I thought or left or right. I can see why almost everyone in this era is using some sort of pinpointing device. I have to get one of those because it took a long time to find the coins I semi- pinpointed.

I read cybersage's post about his Correlate program ( which I am definitely going to put on the V3i after a bit more on-the-search training ) and at the bottom he mentions that VCO should be 'On' instead of the 'Off' factory default in the 'Coin & Jewelry program.
That is probably something I need to check first thing tomorrow. Thank you very much Jack.

My question is however - What is VCO? I have been reading everything I could everywhere that references that acronym. Even a 'Search' on forums and I still have no idea. The Owner's Guide reference's it but does not say what it is. All I know it has something to do with audio.

Anyone please :confused:

[Lowjiber]

Welcome aboard the forum.

Short questions are often the hardest to answer, but I'll try...

VCO = Voltage Controlled Oscillator. It's an electronic device that many manufacturers add to the pinpoint audio function. It simply produces varying audio outputs based on target voltage.

If your coil's center is directly over a target, the target voltage seen by the detector is at its peak. Therefore, the pitch of the audio output of the VCO is the highest. If your coil is not centered over the target the audio output has a lower pitch since the target voltage is not at its maximum.

As you sweep your coil across a target, the sound (driven by the VCO) increases as the center of the coil approaches the target...the loudest sound is produced when the target voltage is the highest (hopefully when you're directly over the target).

Obviously, depth plays an important part. A coil directly over a quarter at six inches will have a lower target voltage than the same quarter at one inch. That same quarter lying just below the grass will often drive the target voltage (and subsequently the volume of the output response) very high...resulting in an unpleasantly high pitched sound in your headset. Many headsets contain a limiter switch that keeps your ears more comfortable when pinpointing a very shallow target. (I use my limiter switch a lot in parks.)

If you turn VCO off, the machine will simply grunt when the target voltage appears under the coil...not necessarily centered. By having VCO on, you'll get a rise in the headset as the center of the coil approaches the target.

Sorry for the somewhat crude explanation, but it's my first cup of coffee at 4:30 am. :interesting:

[silysavg]

Welcome aboard the forum.

Short questions are often the hardest to answer, but I'll try...

VCO = Voltage Controlled Oscillator. It's an electronic device that many manufacturers add to the pinpoint audio function. It simply produces varying audio outputs based on target voltage.

If your coil's center is directly over a target, the target voltage seen by the detector is at its peak. Therefore, the pitch of the audio output of the VCO is the highest. If your coil is not centered over the target the audio output has a lower pitch since the target voltage is not at its maximum.

As you sweep your coil across a target, the sound (driven by the VCO) increases as the center of the coil approaches the target...the loudest sound is produced when the target voltage is the highest (hopefully when you're directly over the target).

Obviously, depth plays an important part. A coil directly over a quarter at six inches will have a lower target voltage than the same quarter at one inch. That same quarter lying just below the grass will often drive the target voltage (and subsequently the volume of the output response) very high...resulting in an unpleasantly high pitched sound in your headset. Many headsets contain a limiter switch that keeps your ears more comfortable when pinpointing a very shallow target. (I use my limiter switch a lot in parks.)

If you turn VCO off, the machine will simply grunt when the target voltage appears under the coil...not necessarily centered. By having VCO on, you'll get a rise in the headset as the center of the coil approaches the target.

Sorry for the somewhat crude explanation, but it's my first cup of coffee at 4:30 am. :interesting:


Lowjiber,

Thank you for taking the time to write up such a good explanation. I am probably 98% in understanding now of what VCO is all about. I'll have to figure out if there is a way to adjust the audio sound of the VCO feature.
Possibly the problem with being certain of the target being directly under the center of the searchcoil has something to do with the nature of the length of the sound, the pitch and the tone.
I am used to the way my old detector just had a short beep when I was directly over the target. You did not need to process a rise or decline in pitch when the coil was moved about over it. I would love to determine if there is a way to adjust the VCO so that there is only a short sound like I am used to hearing.

I know the bar graphs and depth reading are indicators of how close you are to being pinpointed but a short beep would be faster to process I think - less sound length equals less sound processing by my brain and less chance I processed it slightly wrong. Hence, no off-center targets in the hole.

On another note, being new to the forum, I am still learning how to use certain features. I believe I sent you a PM last night requesting The Book of Jack but I do not know for certain that the PM actually went through. Just in case it did not, could you lead me to a way I could get it?

Thank you for taking the time to explain.

[Lowjiber]

On another note, being new to the forum, I am still learning how to use certain features. I believe I sent you a PM last night requesting The Book of Jack but I do not know for certain that the PM actually went through. Just in case it did not, could you lead me to a way I could get it


I got your PM. The updated version should be in your email now. If not, please advise.

[Hunt4Fun]

I have not discovered a way to set the V3i to beep while pinpointing like the old White’s Classic detectors. I won’t say it cannot be done but it will take someone above my paygrade to do it.

Like Lowjiber said, you will be well served by headphones with a “limiter circuit and switch”. While pinpointing, shallow targets will be very loud. The volume can be reduce and the center of the target found more easily using a technique called detuning. During pinpointing, as the volume starts to become quite loud, stop moving the coil holding it still, release and resqueeze the trigger and the volume should be reduced. Proceed with the pinpoint and you will discover the loud area is now smaller. Detuning can be done more than once to further reduce the loudest signal area. Be advised you can go too far and completely silence the signal having to start over.

Hope that made sense.
Bob

[Lowjiber]

I have not discovered a way to set the V3i to beep while pinpointing like the old White’s Classic detectors. I won’t say it cannot be done but it will take someone above my paygrade to do it.

Like Lowjiber said, you will be well served by headphones with a “limiter circuit and switch”. While pinpointing, shallow targets will be very loud. The volume can be reduce and the center of the target found more easily using a technique called detuning. During pinpointing, as the volume starts to become quite loud, stop moving the coil holding it still, release and resqueeze the trigger and the volume should be reduced. Proceed with the pinpoint and you will discover the loud area is now smaller. Detuning can be done more than once to further reduce the loudest signal area. Be advised you can go too far and completely silence the signal having to start over.

Hope that made sense.
Bob


It's funny you used the word &quot:grin:etune. I just replied to another post in the E-Trac section and offered detuning as a possible solution to a question about a detector that I don't really know squat about. LOL

[silysavg]

I have not discovered a way to set the V3i to beep while pinpointing like the old White’s Classic detectors. I won’t say it cannot be done but it will take someone above my paygrade to do it.

Like Lowjiber said, you will be well served by headphones with a “limiter circuit and switch”. While pinpointing, shallow targets will be very loud. The volume can be reduce and the center of the target found more easily using a technique called detuning. During pinpointing, as the volume starts to become quite loud, stop moving the coil holding it still, release and resqueeze the trigger and the volume should be reduced. Proceed with the pinpoint and you will discover the loud area is now smaller. Detuning can be done more than once to further reduce the loudest signal area. Be advised you can go too far and completely silence the signal having to start over.

Hope that made sense.
Bob


Hunt4Fun,

I understand your response completely. I don't understand the detuning concept however. Probably not important to understand the concept as long as it works. I'll try it in the next day or two, weather depending.

Once detuned so that the pinpoint signal is 'smaller' does it stay that way for other targets during that hunt? If so it would be a good thing.
If not I don't think it would be because I can not see myself detuning, such as described, for each target I believe is worth digging.

Headphones are on my wish list. I just have a set I bought at Best Buy. They are not the best but it was all I was willing to spend at the time because I was just re-entering the hobby and needed something to attach to the Garrett Masterhunter ADS III to see if I really wanted to start MD'g again.
After finding a Mercury dime each day of 2, for only one hour forays each, I got hooked again.
lowjiber's and cybersage's write-up's took me over the edge. Went then and bought the V3i. Not the headphones though because I don't know which earphones to buy yet.

Mike

[Hunt4Fun]

silysavg,

I am not an engineer nor electronic tech so I cannot explain the, under the hood functions, how a detector does what they do. It is sort of like I do not have to know how an automatic transmission changes gears to be able to drive my car.

First of all, each detuning only lasts as long as you hold the trigger switch squeezed. Once the trigger is released, the trigger springs back to the center position and the detector goes back into the normal search mode.

Detuning takes a lot of words to explain. It only takes a second to perform. Once you get the hang of it you will start quickly performing the technique without even having to think about it. Spend some time learning the technique and it will greatly improve your pinpointing.

I suspect the search coils you were using in the 80s were concentrically wound search coils. Concentric coils are usually round and their hottest signal reception location for both search and pinpoint mode is in the dead center of the search coil. The 10 inch coil that comes with a V3i is a DD coil design. The Hot signal reception for this type of coil is along the center LINE from the toe to the heel, front to back, of the search coil. When pinpointing with a DD coil, it is fairly easy to center up the signal from side to side but much more difficult to center up from front to back. For that reason, pinpointing with a DD coil is a 2 step operation. Step one, center up the pinpoint side to side and draw an imaginary line on the ground from toe to heal of the coil. Step two, step to the side so you are at 90 degrees to the target and center up the target side to side again and again draw an imaginary line from toe to heel of the coil. Where these two imaginary lines cross in the pinpointed location of the target.

It is much easier to pinpoint with a concentric coil than a DD coil. With time and a lot of practice you can learn to pinpoint with a DD coil using the concentric coil technique but it is much more difficult and takes more patience. While learning to use your 10DD I suggest you use the 2 step technique.

You have LOTS to learn while becoming familiar with your V3i. As you gain experience, you will then recognize that quality headphones, with a limiter circuit, will help you progress.

You have a great adventure ahead of you.
Bob

Hi Lowjiber,

It is funny how specific topics or phrases seem to occur in clusters.

May all your finds be great ones.
Bob

[Vito]

Sorry for disagreement :blush:, but I think here are two things mixed up. It's VCO and audio modulation.

As mentioned by the previous writers, the VCO will change the pitch of the audio if the target strength (distance) changes to the coil.
And the audio modulation will change audio volume on the target strength.

Both can be changed (on/off) on the whites xlt, dfx & v3(i).

So modulation [off] can help to announce the deeper targets with the same volume level as the shallower targets will do.

[tumbleinn]

VCO- Provides a varied pitch based on target depth & or position in relationship to the search coil for the all metal protion of the stero mixed mode. it also can be turned off and on when used witha dx-1 probe. you can change the dx-1 probe over to search mode or pinpoint mode doing this.
Good Luck!