Challenging Technical Question about the Radiometer Ferret

[Randy Seden]

Looking at all the information on the "Detecknowledgy"


site for the Radiometer Ferret and it's superior performance when compared with all other kinds of metal detectors, I would like to know if anyone has built one yet? Secondly and more important, if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold? As I was looking at the diagram I quickly realized that he basically built a PLL CKT.,and a 4046 would do the job nicely (check out the Philips updated version of the ol' 4046 at www.philips.com. Their part number is 74HC/HCT4046A).

[rick]

Re: Challenging Technical Question about the Radiometer Ferret

me shut up--blab too mutch--someone else can talk--
if no one does,in time,me say to you..(some say
dont that guy ever shut up)


reg-rick


>Looking at all the information on the "Detecknowledgy"
>site for the Radiometer Ferret and it's superior performance when compared with all other kinds of metal detectors, I would like to know if anyone has built one yet? Secondly and more important, if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold? As I was looking at the diagram I quickly realized that he basically built a PLL CKT.,and a 4046 would do the job nicely (check out the Philips updated version of the ol' 4046 at www.philips.com. Their part number is 74HC/HCT4046A).

[Don]

Re: Challenging Technical Question about the Radiometer Ferret

RE: >...Secondly and more important, if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold?


----------------


It is not optimized for copper. The frequency (range) selected has everything to do with optimizing and compromizing the design parameters to achieve the desired functions most reasonably, and nothing to do with a specific metal. The frequency could as well have been 20 kHz or 16.999 kHz.


This isn't a MFD type, magic frequency device.

[Don]

Re: Challenging Technical Question about the Radiometer Ferret

>RE: ...Secondly and more important, if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold?


>----------------


>It is not optimized for copper. The frequency (range) selected has everything to do with optimizing and compromizing the design parameters to achieve the desired functions most reasonably, and nothing at all to do with a specific metal. The frequency could as well have been 20 kHz or 16.999 kHz.


>This isn't a MFD type, magic frequency device.

[Don]

Re: Challenging Technical Question about the Radiometer Ferret

>RE: "...if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold?"


------------------


It is not optimized for copper. The frequency (range) selected has everything to do with optimizing and compromizing the design parameters to achieve the desired functions most reasonably, and nothing at all to do with a specific metal. The frequency could as well have been 20 kHz or 16.999 kHz, or less. This is not a MFD type magic frequency device.


If this post shows up more than once, I apologize in advance. I seem to get into trouble when I try to "preview" a post.

[rick]

Re: Challenging Technical Question about the Radiometer Ferret

hi randy--


have you tried to query the author..


me no make it. enhanced preformance--would not hold
my breath..18khz for cu au ?----cannot say---
no doubt you have brochures from the major manufactuers and have noted the general higher
frequency used for what they say is a gold detector.
and also that the different coil geometry...how much
is hype---apparently the more difficult issue is
that of the matrix where gold is usually found..the
coil geometry being critical--a dd design..


my homemade vlf was origonaly designed for three
frequencies---appox.--1.5khz,7.5 khz,15 khz...
the coil design is modeled after whites blue max..
a simple concentric ib..work on the unit is still
in progress as decided to add a microprocessor
to give indications on a lcd display...within
the range of freq. stated decided after considerable
testing to just have at 7.5khz....the differences
being small but noticeable in terms of depth/responce
etc..the electronics are origonal.


hope this helps..


reg-rick

[Carl]

Re: Challenging Technical Question about the Radiometer Ferret

>Secondly and more important, if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold?


I don't think he was saying 18KHz is the optimum copper frequency. It appears that he pulled 18KHz out of the bag and then showed it to be acceptable for copper, and only from a skin depth perspective. (He also showed 100KHz to be acceptable as well.) Skin depth is important for good amplitude response.


He did not consider the phase response of the target vs. frequency, which is just as important. This aspect will determine sensitivity and the ability to discriminate. He also did not account for earth penetration vs. frequency, esp. under mineralized ground conditions.


There are a lot of things to consider when choosing the frequency, and Rick's approach of having several makes sense. I plan to eventually use a multi-frequency method with sampler and DSP so that I can see the response of a target to several different frequencies simultaneously. I think this is the approach Minelab uses.


- Carl

[rick]

Re: Challenging Technical Question about the Radiometer Ferret

hi carl--


I plan to eventually use a multi-frequency method with sampler and DSP so
that I can see the response of a target to several different frequencies simultaneously. I think this is
the approach Minelab uses.


when you do certainly hope you would post your
findings/hypothisis/conclutions...this could help
others in that the cursory experimentations will
be minimized---


reg-rick


>>Secondly and more important, if 18KHZ is optimum for finding Copper (Why he bothered doing the calcs for a relatively useless metal like copper instead of Gold I don't understand), what would be the optimum frequency for finding Gold?


>I don't think he was saying 18KHz is the optimum copper frequency. It appears that he pulled 18KHz out of the bag and then showed it to be acceptable for copper, and only from a skin depth perspective. (He also showed 100KHz to be acceptable as well.) Skin depth is important for good amplitude response.


>He did not consider the phase response of the target vs. frequency, which is just as important. This aspect will determine sensitivity and the ability to discriminate. He also did not account for earth penetration vs. frequency, esp. under mineralized ground conditions.


>There are a lot of things to consider when choosing the frequency, and Rick's approach of having several makes sense. I plan to eventually use a multi-frequency method with sampler and DSP so that I can see the response of a target to several different frequencies simultaneously. I think this is the approach Minelab uses.


>- Carl