please read this message on frequencies

[William1221]

OK guys thanks for the onfo on the previous message. I'm learning a lot! In my hot little hand I have a Tesoro Catalog.
I'm not understanding the difference frequencies or example for coin and jewelry hunting almost all of the machines rate 3 star for the best machine to use,although some have different frequencies. It doesn't make sense that all of them would be rated that high. There has to be one that hat is better than the rest?????

Compadre 12KHz 3*
Silver Max 10KHz 3*
Cibola 14.3-14.7KHz 3*
Vaquero 14.3-14.7KHZ 3*
Golden Max 10KHz 3*
Lobo Super Traq 17.5KHz 2*
Quartz 10KHz 3*
Sand Shark 600PPS 1*
Tiger Shark 10KHz 3*
DeLeon 10KHz 3*
Tejon 17.2-17.6KHz 3*

 

[William1221]

sorry should have been Cortes not Quartz

 

[hrsetrder]

I have always wondered about that to. I have found more gold rings using a Silver u max (10 khz) , than I have with any other detector. I have used alot of Tesoros , but seems like the Silver Umax was always producing rings, even though other Tesoro units operate at 10khz? It is confusing to say the least with the frequencys. I plan on going back to my simple Silver Umax , and forget the rest. I have found more with that unit than any I have used , fact it bought three other units with the finds. I plan to hit some ball fields with the clean sweep this spring. In my opinion if you are after coins and jewelry, then stick with 10khz freq. If you are after relics , go with 14khz and up. Whites seem to go after jewelry at 7.5khz or so? I dont know the magic behind the circuits , but 10 khz seems to work best for me and my type of hunting.
HH , David

 

[William1221]

I think your are on to something!Perhaps if we found out the frequencies that produced the results we want ie gold ,relics, nuggets, would be a better way of getting the results we want. How abouut more input.

 

[rentasquid]

Most gold detectors are from 15-80 kHz. Silver responds best to the lower numbers ~ 3-10 kHz. I was told that Tesoro designed their detectors to be in a midrange. JB(MS) has posted some good stuff about this in the past. Here is a quote that he posted from George Payne.....
"The target signal returned to the receive coil can be thought of as composed of two components, one we call x and one we call r. The polarity of the x signal (its direction) tells us if the target is ferrous or non-ferrous. The r signal has only one polarity. Also, the ratio of the x and r signal tells us the target

 

[hrsetrder]

Good info , but gold detectors are not gold ring detectors. They are designed for nuggets. Gold rings have a mix of alloys along with gold, here is where the difference is. Here is some info. on gold detectors I found with a web search. Gold nugget detectors usually operate in between 18 Khz to 71 Khz range. Many people think that the higher frequency is better to have. But it all depends on the soil conditions. Fist of all, we can change a frequency of a gold detector from (for example) 18 Khz to 90 Khz by changing a Crystal or a Capacitor or an inductor. This can cost less than $1 worth of components. I personally like 20 Khz range detectors for Gold nuggets. Because, If we go higher than that machine would be so sensitive that will die in black sand. Dealers, usually like to sell 40- 50 Khz detectors because they show a very good air test. On my opinion, Air tests are the worst way of showing the performance of a detector especially if the detector is a gold detector, because a good gold detector is for black sand conditions (not air) to operate. If detector is in 50 or higher frequency range, Signal will bounce easily by black sand, because sensitivity is high and machine thinks of black sand as small nuggets. Here is the catch, It is easy to build a detector in any frequency we wish, but it is very hard to control the effect of minerals in higher range, unless our design has some filters or circuits that can eliminate black sand and mineral response. So far there is only one high frequency (71 Khz detector) which has met the standards and that machine is the 'gold bug II'. Gold Bug 2 can eliminate the effect of black sand to a degree, that is the best you can get among high fre. detectors. If you cannot afford it, then the 20Khz gold detectors are perfect. Lower freq. can detect bigger objects deeper. High freq. cannot go deep because of minerals in the soil(signal will be reflected)thefore we will miss big nuggets but in exchange we will get small nuggets just on the surface. If you are moneywise, then, you like the big nuggets, not the tiny ones. With high freq. you will loose depth in mineralized soil, and you will sweep over many nuggets without detecting them. Think of high and low freq. as 'light' and 'radio'. light is high freq. Radio waves are low freq. ( with respect to light). Light cannot pass though most objects and reach the target, but you can still listen to radio in a submarine. That is the defference. I will have more on lower frequency detectors in the next post.
HH , David

 

[saika]

Some questions that I have to add is:

How do the harmonic frequencies come into play, if at all?

Am I correct in my thinking that part of the compromise is using frequencies that work out to harmonics of some of the "best" frequencies for responding to certain targets? Is this how some detectors claim to be using multiple f or are they actually workng on multiple frequencies at the same time? This has always kind of confused me.

Merry Christmas to all!

 

[hrsetrder]

I have determined that 10khz seems to be the best all around frequency for general hunting (coins,jewelry ). After all Tesoros big boys (Cortes) use this freq. as well as the lower priced models. I wanted to add that in my previous post I mentioned how well the Silver U max produced rings. I ran this unit at 8 on sens. , and set the disc. at just a tad bit below 5 cent mark. This produced many , many nickels as well as rings with minimal tabs. However small thin diamond rings will only signal at around the O in the foil mark. If you are not digging tabs , your not digging gold rings or nickels with any machine. Any machine will be fooled buy a tab , this problem will never go away , unless the soda can companys start using plastic tabs. They eliminated the pull tabs that had the tails , but people still think they have to rip the attached ones off and litter the grounds with them. In my opinion , if you want rings , be ready to dig alot of tabs and dont worry about what you read about fancy programs.com , freqs., or the next gadget. A pull tab will always fool a detector no matter how smart it claims to be. If it dont , then your disc. is to high and you are missing the rings. I have a friend that runs high disc. everywhere he goes on purpose. He cherry picks the dimes and quarters and never looks for anything else. He trades the clad for silver coins (buys silver with clad he finds) and has a mass collection from doing this. He said once he gets his silver collection high enough , he will trade it for some gold.
HH , David

 

[William1221]

1. Being a beginner in this hobby I have multiple questions. How can the -3db frequency be the same for two different alloys such as a dime and a penny 2.7khz ?
2.Would a multi frequency coil be better?
3.How about a detector that has a frequency of 12khz to perhaps 80khz?
4.Would an external dial with different khz settings be useful.With this kind of arrangement could you dial out black sand, concentrate on a specific target,Increase your sensitivity by changing the khz settings and make it more compatible to the ground? Would it help ground balance the machine better?
5. I often read , having to reduce sensitivity for smooth running. How does (4) fit into this picture.
6. How about changing the way we think abt metal detectors?Giving the user more control over the machine instead of the machine over you.
7. How does discrimination fit into the formula?
PLEASE REMEMBER I'M beginner and a terrible typist. These just happen to be questions that have spurred my interest. I enjoy constructive criticism and never mean to make folly of anyones answers. Just trying to learn. Bill

 

[rentasquid]

I know that I cant fully answer all your questions, because I dont completely understand electronics enough. I can understand most of the quote that I posted, but there are points there that I have a hard time wrapping my mind around. Here is a feeble attempt to answer a few of your questions...

1. I think that the alloys that you mentioned are similar enough for them to be at the same frequency. I dont think that George was saying that these were silver dimes and pure copper pennies. As you probably know, they are amalgams of metals, and they probably have similar components for both coins.(just with different skins)

2. The coil works as a transmitter and reciever for the signal generator. If the coil has multiple signals sent to it, it can send and receive several signals. It is just an extension of the main electronics.

3. The 12 vs. 80 frequency is what George was comparing in the body of the text, where 12 would be a better frequency to detect silver and the 70 would be better for gold. Therefore, you design the electronics around what you want to detect for.

4. Dialing in your electronics? I'm not sure, but some of it might have to do with the coil needing to be "tuned" to a certain frequency. Thats why you cant use the higher frequency coils(Tejon, Vaquero, Cibola and LST) on the other micromax detectors and vice-versa. The second factor may lie with the FCC and their rules and regulations. This is strictly a un-informed guess though.

5. I think the sensitivity is what helps keep your sanity. If the sensitivity was increased too much the coil would respond to any abberant signal in the same manner as a good signal, giving innumerable pops and clicks and such.

6. Most detectors are pretty adjustable, but interestingly enough, it is often the simpler detectors that are the most widely used, because you can just turn them on and go. That shortens the learning curve and allows people to just go out and dig, rather than tuning this and balancing that, etc.

7. Discrimination only fits into the equation in that is allows you to hear certain signals, and ignore others.

I hope that I havent exposed my own ignorance too much. If our wells of knowledge(i.e. Monte, JB, Scully, Ralph and many others)jump in here than maybe they can help explain these points a little better.

J.

 

[JB(MS)]

What you posted came from the Discovery Treasure Baron page on my website, or the archives of Carl's equipment forum which is also on my website, and was written by George Payne, who you probably know about. He invented ground balance, motion detectors, discrimination, analog and digital ID meters, multi tone audio and built the first computerized detector. He says the frequency selected for any detector is a compromise, for the very reasons listed in the text you posted. He also says that frequencies between 10 and 15 khz are the best compromise for general detecting because they respond to all metals better than higher or lower frequencies. Frequencies in that range or higher aren't as good for finding high conductive metals, silver or copper coins for example, as lower frequencies and don't go as deep in moderate to higher minerlization as lower frequencies, and aren't as good as higher frequencies for finding lower conductive metals, nickels, gold rings, etc., but will work better for metals in both conductivity ranges than either a higher or lower frequency will. Both he and Gary Finch did extensive tests using different frequencies, both in the field and with Oscilloscopes, and both settled on 12.5 as the optimum single frequency for detecting all metals. That's why George used 12.5 khz for the Discovery Treasure Barons.

In answer to William1's question as to why dimes and copper pennies have similar -3db frequencies: It's because they have similar conductance properties, and detectors classify targets in the discrimination range based on their conductivity.

The article you got the info from is on my website, down toward the bottom of the page in an article titled "Why a VLF ground balanced detector has less sensitivity to higher conductive targets in the all metal mode", at http://www.jb-ms.com/Baron/payne.htm. It's an interesting article, as is the one he wrote on ground balance and coils at http://www.jb-ms.com/Baron/gb.htm.

 

[rentasquid]

and my apologies for taking any material tied to your site without your permission. Thanks again for the info!!!

J.

 

[William1221]

Would like to comment on the numbered information on this thread by william1 We are are all here to learn. thanks

 

[JB(MS)]

I guess my post did kinda make it seem I didn't want anyone taking anything from my website. I didn't mean it that way and don't mind at all anyone using any info they find useful from there, but if anything George wrote is used it probably should be noted. By the way, I noticed you signed one post as J Brown, that's also my name.

 

[JHM]

n/t

 

[DavHut]

This has been tried with limited success. It has been abandoned, for now. There are too many "tuning" factors that have to change along with the frequency for it to be practical. Not the least of these is the coil dimensions, but other complex circuitry parameters, too.

 

[rentasquid]

To have two names like that! My J. is all there is to my first name. My parents thought that it might be easier than Jay to remember?!?

J.

 

[Robby41]

My 2 cents...As has been stated, the r & x factors will always
be affected by ground mineralization with differing frequencies,
especially concerning discrimination settings for various
conductances. Years ago, Whites called their first ground
balance controls "ground attenuation". In electronics jargon
this means (Webster's); "To reduce(the amplitude of an electrical
signal)with little or no distortion". For all intents and
purposes, this is still the basic function of GB controls {to
reduce the mineral ground effects upon the conductance signals
to the receive coil}. The Higher frequencies will be limited in
depth and thusly the recognition of signals from smaller lower
conductance targets, while the Lower frequencies will get more
depth in the mineral matrix, but mainly on larger targets of
higher conductance.
These "trade-offs" will always exist with VLF's, with the afore
mentioned best average frequency probably being 12.5 kHz. So part of
the fun and interest of detecting is in trying out these different
factors in relation to various ground matrices to experience the
best results. It will always be so, until a more advanced disc.
circuit is developed for Pulse technology(no breath-holding please!)
..R

 

[christian_99]

The higher the frequency the better response to small gold and signals will be....that is why with all of these and some of the finds that the Tejon has made seemed to be correct concerning some great button collections that have been machine. IMHO

 

[popsmoke]

From 12khz to 10khz or even to 17khz cannot be that big of a difference in as far as a detetors abilty to to detect a silver dime, gold coin, or a gold ring, or a minnie ball.
Am I wrong - but we are talking subtle differences if any.

I can see from 12khz to 80khz as in the Gold Bug II, but the Tesoros operate in the same range - 14khz +- 3khz.

Does it make that much of a difference?