Any recommended settings for the F70 in Gold country, Northern California?

[vincentvangerven@gmail.com]

Have obtained a fisher f70 and it's stable when air testing, but when I put the coil to the ground in my heavily mineralized soil it's going haywire, very chatty.

Any users of this machine in my area who have some recommendations?

Another thing that I noticed is that with just about any setting I tried it will identify a small balled up gold necklace as iron, with a iron tone and number 7 on the screen.

I know small gold typically scores lower on the chart but i was a bit surprised since the detector was once marketed to even be usable for gold prospecting

Thanks

 

[Picketwire]

The threshold adjustment is your friend. If it is too chatty in disc, turn it down and it will quiet down. If in all metal, turn the sensitivity down until the threshold smooths out. It is not surprising that a small chain of any metal would ID as iron, even the smallest nuggets will too. Heavily mineralized soil necessitates lowering of sensitivity on high powered detectors.

 

[vincentvangerven@gmail.com]

Thanks for the input! I found quite a few useful posts online about this detector, which is helping me understand the unit a bit better. I tried the chain with a Tesoro Tejon and Conquistador and got the same result, being the detector ID-ing the chain as iron.

Thought the F70 might not do this since I see it advertised as a suitable candidate from prospecting, but I can't say it's doing anything different than the previously mentioned Tesoros.

Still having fun learning the F70

 

[jmaclen]

Thought the F70 might not do this since I see it advertised as a suitable candidate from prospecting,

Even the latest simultaneous multi frequency detectors will detect small gold chains very low on the target ID scale right around the ferrous/non ferrous tone break. As stated above by Picketwire, smaller low conductor targets like gold and lead that weigh less than 0.25 grams may be detected with non ferrous responses in air tests but they will likely have ferrous responses in magnetite mineralized ground unless they are really near the surface.

I do detector prospecting a one site here in Colorado where modern US clad coins used for testing there will have ferrous target IDs if buried deeper than 5" in that highly magnetite mineralized dirt even using the latest SMF detectors. An F70 is definitely going to call those coins as iron if it can even distinguish them from the ground itself at that site.

It's been a long time since I owned and F70 but I do keep records and it air tested a 0.25 gram gold nugget at 1.5" in all metal. I would expect it to do a little worse on a 0.25 gram target in higher mineralized ground. Part of that result is the F70's 13 kHz operating frequency. Detectors that can run at higher frequencies, 20 kHz and higher are more sensitive to smaller low conductor targets and may be able to hit smaller targets better in higher mineralization too. Detectors with the latest simultaneous multi frequency operation can be run hotter and more stable by comparison since they are very capable of running stable on hotter ground at higher sensitivity, so they are even more sensitive to really small low conductor targets.

Back in 2008 when the F70 was introduced, there were more near surface gold nugget targets that an F70 could hit easily than there are now at least where I detect.

The F70 with a smaller coil will be easier to ground balance and can run more stable on hotter ground. What coil are you using?

A 0.25 gram gold nugget is a decent sized picker where I detect and there aren't too many of them left near the surface here as well as anything bigger unless I get extremely lucky.

 

[vincentvangerven@gmail.com]

Thanks for the input! Took it out today after reading a few more tips and tricks found online, and it's starting to click: managed to run it hot but stable this time around. This especially helped, I think Dankowski wrote this at some point:

THE BEST WAY TO REDUCE EMI:

Place F75 in all-metal mode with max Sens ('99'). Hold coil about a foot above the ground.....very still......and perfectly parallel with the ground. Select F1 through F7.........one at a time...... and listen to each channel/freq for about 4-5 seconds. Find the one freq/channel that provides the least interference. Now you can switch back over to the ID mode......and.....yes......this Freq/channel selection will stay the same whilst switching over to the ID mode. If you are running the unit 'wide open'....and you still are encountering EMI..... you can change Disc to a setting of '5'. There is a huge difference between Disc '4'....and Disc '5'. You should not have to increase Disc to higher numbers. If EMI is still present.... you now can start to drop Sens .... until EMI is gone. Remember; you are already on the best possible F1 through F7 Freq/channel selection...and must employ other methods so as to reduce EMI... if it is still present.

If you look at your LCD depth bar-graph......and EMI is causing it to jump all the way into the middle bar-graph (medium strength signal) ............you will only be able to detect targets that are (at least) as strong/powerful.....OR STRONGER (shallower) as that middle bar-graph. This is also to say that......if you want to get rid of audible EMI......you would then be required to reduce Sensitivity to the point where targets in that middle bar-graph (and deeper targets)... would no longer be detected. What you are doing is.....reducing the sensitivity of the detector to 'just below' the signal strength of the EMI. Said differently; If EMI is so strong......that this specific EMI "looks like" a 7" deep target................then the detector will only be capable of detecting targets up to 7" deep....and no deeper... in this hunting area.

Some of the best days to hunt.....as far as EMI is concerned......is at the very end of a hard rain........or shortly after a hard rain......as this is what washes the salts off of nearby powerlines.

If you are 'beating' an old/hunted-out area again.......and you suddenly learn that you are finding a lot more targets........it may very well be that you are encountering less EMI on this specific day.

I can only stress the level of importance of EMI mitigation. USE THAT F1 THROUGH F7 OPTION.

&

When absolute maximum overdriven performance is desired:

1) Starting point = Factory Preset and Ground Balance.

2) Hold coil parallel to ground.... and at a height (approx) 8" above the ground. Do not tilt the coil upward. Increase Sens to '99' and verify detector is audibly stable. This is the FIRST step. (((Shut down your intents if you cannot ascertain stability with Sens on '99'))).

3) Next....... IF no EMI is encountered with '99' Sens........ THEN you may start to bring Disc down. Start with Disc '6'.

4) IF the detector is still EMI stable.... see what happens to EMI stability.... by lowering Disc BELOW '5'. '5' is not the magic number.... but '4' is. Going to a Disc setting of '4' is where sensitivity receives yet another boost. (((And USUALLY............... when you are at a Disc of '4' ... and ESPECIALLY lower... is where multitone option is virtually required))). Set Disc on '4' and verify detector remains audibly stable.

5) Now, Drop Disc to '3'... then '2'... then '1'... then ultimately '0'.. verifying audio stability is still retained.

6) Now select JE mode and verify detector remains audibly quiet.
((( IF .... during any of these steps, the detector becomes audibly 'chattery' .... you have electrical interference (EMI).... and must back-up in procedure,,,,, until you re-find electrical stability,,,,......,,,,,,, and these are the settings you should hunt with ))).

7) Start sweeping the coil..... with the coil remaining 8" above the ground,,,, and verify detector remains audibly stable.

Start lowering the coil closer to the ground while continuing to sweep....and verify detector remains audibly stable. If you manage to get the coil all the way down onto the ground while sweeping..... and the detector is audibly stable,,,,, you are home-free!!!!... and have the most powerful relic detector currently on the market. Remember, many relics are very low conductors (in the 'foil' range).

((( IF..... while lowering the coil to the ground as you are sweeping,,,,, and the detector THEN becomes audibly unstable..... you have ground interference ... most probably from high volumes of tiny flakes of rust/iron (a VERY common dirt occurrence)..... which then, you must back out of the JE mode ))).