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F-75 as a prospecting unit-Tom need your opinion

Posted by HumblePie 
F-75 as a prospecting unit-Tom need your opinion
April 07, 2008 06:00PM
Hi NASA-Tom,

I'm new on this forum and would like to thank everyone for their informational posts. I've been a relic, coin, and jewellery hunter, and hobby prospector for some 22 years. I'm considering updating my detectors to include the F-75 for gold/silver prospecting.
The F-75 seems to have the necessary features for prospecting, such as a decent operating frequency at 13 kHz, the all-metal modes, manual ground balance (quite useful for dealing with positive hot rocks when required), lightweight for my not so young elbow, low power requirements, and the visual display is an added bonus as an aid to iron junk identification (not to mention it's value should the unit be used for coin hunting). It is also a sensitive unit by all accounts.
Most of it's use would be on abandoned mine tailings. I'm aware this unit was primarily designed as a relic/coin hunter, but I've an idea it might do well for prospecting.
My primary concern, based on a number of postings on various forums, is that this unit may be too noisy/unstable to be a practical choice. I can't help but think that surely the sensitivity could be adjusted to provide stable, smooth performance in one of it's process modes...but without any chance to try one out beforehand...I just don't know. Can you please provide me with your views on this subject. Many thanks...Jim Hemmingway.
Re: F-75 as a prospecting unit-Tom need your opinion
April 07, 2008 08:09PM
I'm probably not the correct person to ask........ as I compromise NOTHING! If I were to prospect, I would not acquire a 'general purpose' detector (that's fairly good at many hunting types),,,,,, for one of the toughest types of hunting. Although the F-75 is VERY good on somewhat small gold; I would still be much more heavily biased/inclined towards a Gold Bug-II..... or,,,, better yet; the Minelab SD series....or,,, especially the GPX-4000. Life is too short.....and if you are to spend your limited precious time prospecting; do it right the first time!

Re: F-75 as a prospecting unit-Tom need your opinion
April 08, 2008 02:31AM
Hi Tom,

Thanks very much for your views on the subject. In retrospect, perhaps I should have worded the question differently; regardless, the question was sincere. In an effort "to do it right the first time" I have researched all the leading prospecting units, including the F-75 as a potential candidate.
The Minelab ground balancing PI units are currently the leading choice for larger gold in high mineralization, where single frequency VLF's do not fare as well. In addition to acquiring a PI unit for that purpose, I intend to purchase an up-to-date VLF for small, shallow gold (where PI's do not do especially well).
A number of the VLF prospecting units on the market do not even have manual ground balance, for example, Tesoro Lobo, Minelab Eureka, White's MXT. The White's GMT while having a subtle iron identification system, does not have a discrimination circuit, and is not the best choice for the type of iron infested tailings I will be searching. The Goldbug2 is a good choice, everything considered, since it does provide an iron disc setting and is very sensitive to tiny gold; however, it's depth ability suffers somewhat in highly mineralized ground. Finally, I already own a Garrett's Goldstinger, which is quite adequate for large ore searching, but lacks sensitivity at depth to smaller targets.
That leaves the F-75 for consideration. It offers many features the other units individually do not, the advertising does indicate it is suitable for gold prospecting...and my research indicates it should do the job. I am willing to compromise on some operating parameters (for example lower operating frequency) in order to acquire the best overall detector (that more ably fits my requirements) to do the job. There is no one detector on the market that will be suitable for every detecting/prospecting situation, but since I only intend to purchase one VLF unit...some compromise seems inevitable.
Please allow me to rephrase my question. In the all-metal motion mode, can the unit threshold stability be adjusted (say, in areas of moderately high... to high iron mineralization) such that small target whispers are reasonably discernable from any small amount of circuit related sounds?
If anyone else can kindly provide any comment, please do so. Thanks...Jim.
Re: F-75 as a prospecting unit-Tom need your opinion
April 08, 2008 10:00PM
I have config'd the F-75 for prospecting mode; for 'bench' testing only...... and yes, the Thresh is adjustable,,,,, YET....... unless it can be applied/tested in REAL DIRT situations (bad dirt), of which I have never had the opportunity, , , I can give no REAL WORLD test reports. Maybe someone can chime in.

Re: F-75 as a prospecting unit-Tom need your opinion
April 09, 2008 01:23AM
Hi Tom,

Thanks for that effort, most kind. As a prospective buyer, I appreciate getting any information that can add to my understanding of this unit. After reading many of the forum posts, I realize that a prospecting related question is somewhat unusual here; further, I think you've addressed the topic candidly, and as far as reasonably possible, without having verifiable real world results available. Understandably, there is very little information in the literature regarding this unit's prospecting performance, to date.
I enjoy this instructive forum very much, and we are fortunate to have your expertise available to us. Hopefully, others with some in-field experience can offer their views as well. Thanks again...Jim.
Re: F-75 as a prospecting unit-Tom need your opinion
April 09, 2008 05:31AM
Jim and Tom..If I hit any type of gold while shooting the creek banks I will be sure to post..The weather is getting warmer here and prospecting among more relic hunting is in my plans..My job has gotten busy over the last several months..I do plan on visiting reeds gold mine just up the road to learn more about gold and panning..
Tom in your opinion for shooting creek banks and sand bars whats your setup recomendations..I am thinking either all metal or JE mode with 0 disc and as much sense as possible or possibly stat mode..I have the small coil so getting good angles shouldn't be a problem..I haven't heard or read of anyone trying it yet..thanks james
Re: F-75 as a prospecting unit-Tom need your opinion
April 10, 2008 12:50AM

Your set-up config sounds right on target. .... Most importantly, I would bring a small (maybe the size of a air rifle BB or slightly smaller) nugget...... a REAL nugget (not a 'simulated' gold target) and bury it on/near the creek banks that you will be hunting. THEN test different set-up config's (control panel settings),,,,,,,,,........ and you will learn exactly YOUR dirt conditions and what works SPECIFICALLY for you. I think the 'JE' mode will be a "eye-opener" to you....... assuming you can invoke this mode WITHOUT acquiring any form of EMI. If the banks are exceptionally clean/sans of targets, try max Sens motion all-metal AND try "JE", zero Disc & max Sens. In this config..... the F-75 starts to encroach Gold Bug-II perf levels. If you are in any form of ID mode...... make sure you can run your Disc BELOW '5'..... and prefer'b '0'. This is CRITICAL to tiny nuggets.

Re: F-75 as a prospecting unit-Tom need your opinion
April 11, 2008 04:14AM
Thanks tom..The place i have in mind has been known to produce small nuggets..Its farmland..
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