different khz

[Ed Steinhoff]

can anyone tell the advantage/disadvantage of different khz's? most mds use 6.5 or 6.8 but Garrett 250 I was looking at had a 12.5 coil. what gives?

 

[dahut]

What are the benefits? None that matter, really. What you have noted is a tendency toward higher frequencies across the board in the world of hobby detectors.

The optimum frequency for a hobby metal detector is around 13khz. This is a best use compromise, really, splitting the difference between the low and high conductors we are after in the hobby.

Lower conductors, like gold and brass, respond better to freq's around or above 13khz. SO many detectors are designed to respond to them, especially the relic and "small gold" units.

High conductors, like silver coins, hit best on lower frequencies, 2khz-8khz, give or take. This is the traditional range most detectors have used.
This stands to reason, too, since most detectors have been geared towards silver coins, the traditional quarry of the detectorist....

Ground penetration is better with the lower frequencies, so there is a good reason to stick with the frequencies below 13 khz. But, this is offset more and more by today's higher gain circuitry.

I personally think there is another reason for the increase in frequency we've seen in recent years. Simply put, silver coins are increasingly scarce, so most makers have deemed it useful to go more for the frequency band around 13 khz. No one is saying this out loud, but I note a trend or two after 20 + years, you know?

Indeed, most maker have at least one unit that uses what are the higher freq's.... some have more than a few.
A couple of makers have gone so far as to use both high and low frequencies in one unit and one manufacturer even uses many, multiple frequencies to cover all the bases.

However, in practical use, the average detector in the hands of the average user is little affected by any of this.
Modern circuitry, low consumption-high gain electronics and appropriate microprocessors (where used) have made it possible to cater more and more to these upper frequencies without sacrificing much depth (if any).

 

[Uncle Willy]

Different metals respond differently to different frequencies. Gold responds better to higher frequencies.

Bill

 

[Ed Steinhoff]

thanks! that made a lot of sense and cleared up some of my evaluation process. Ed

 

[dahut]

thanks! that made a lot of sense and cleared up some of my evaluation process. Ed

I've borrowed a page from from the Troy website, written by Gordon S. Gibson. I've edited it a bit, to eliminate any bias, as his comments are universal in their application, no matter whose detector you use:

If you have been operating a detector for any length of time you will know that most detectors will find silver and clad coins much deeper than they will find nickels. You will also realize that most detectors are not very good at finding small necklaces. (... both lower conductivity targets- David)

Today, nearly all general-purpose detectors operate from 6 kHz to 12 kHz.
- The lower the frequency number, the deeper the detector will find high conductive targets such as silver, U.S. coins, large gold rings, etc.
- High frequency numbers will be more sensitive to low conductive targets such as nickels, small wedding rings, necklaces and, of course, gold nuggets.
(The Shadow X5 has chosen an operating frequency of 19 kHz, meaning it will have superior sensitivity on the low conductive and smaller targets.)

The frequency story does not end here, though. Designers have developed new electronics that will help amplify the higher conductive targets such as silver and clad coins. What does all this gibberish mean? It simply means that that today's detectors with their higher freq's will find nickels and small wedding rings as deep as dimes and quarters. Now that is really something!

For the full excerpt on the Troy X5 by Mr. Gibson, go here: http://www.troycustomdetectors.com/reviews/x5-gibson-review.htm
NOTE: The Troy line of detectors are not currently in production, as far as I know.

 

[Uncle Willy]

Pretty much all true. I field tested the X5 for Troy some years back when it first came out. It's quite a machine. I've heard rumors he may be working on another. I may email him and see if there is any truth to it. The X5 was manufactured by the original Fisher company to Troy's specifications. His first detector was made by Tesoro.

Bill

 

[coach c]

I was under the assumption that with the Garrett machine, you changed frequencies to quiet down your machine when certain interferences occurred. If I change to a higher frequency, will it pick up gold rings better?.....Coach

 

[dahut]

I was under the assumption that with the Garrett machine, you changed frequencies to quiet down your machine when certain interferences occurred. If I change to a higher frequency, will it pick up gold rings better?.....Coach

In a word, no. It isn't quite that cut and dried.

The frequency shift that you find on Garrett detectors, and most others, is designed to compensate for interference from other detectors and EMF sources. You're right about that. It is typically a close harmonic of the main frequency, and only varies by a small percentage of the main frequency.

For example, a detector that operates at 6.55 khz might have a frequency shift function that allows it to go down to 6.35, or anywhere in between.

This is useful for combating interference, but is not enough to significantly bias response of the detector towards low conductors like gold. I've only seen a few detectors that offer enough frequency variability to broadly shift conductivity response that much. None of them are made by Garrett.

 

[Uncle Willy]

The frequencies you speak of are only minor and in tenths of a degree between two numbers, not from 1 to 50 or 1 to 100.

Bill