Does the threshold setting matter?

[limegoldconvertible68]

The preset on my F70 is -3. I always try to crank it as high as possible but I never can tolerate anything above 0. Being used to my 1265X I really don't know anything about threshold settings. What exactly does it do?

 

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[George (MN)]

The threshold might be considered a stability control, that works together with the sensitivity control.

Here are the lowest settings (air test) that could get a quarter at 8" with a proper ID, DE mode, disc 15

thresh -5 sens 99
thresh -4 sens 70
thresh -3 sens 20
thresh -2 sens 16
thresh -1 sens 12
thresh 0 sens 16
thresh +1 sens 6
thresh +2 sens 4
thresh +3 sens 1

Yes, all these settings are about equal in depth, though not in volume, at disc 15.
The more negative the number, the more depth lost at high disc settings. Settings of thresh 0 or above will have no depth loss on higher disc. In DE all metal, quarter IDed properly at 9" with thresh -9 and sens of 35. The detector can be swept slower without losing depth, using all metal.

None on these settings can be turned up very far in the presence of mineralized ground or electrical interference without getting falsing noises. Turning up the sens can make a small improvement in depth, but may become unstable.

The SL mode will be deeper but separation not as good. SL mode will require negative threshold many places SL disc 25, thresh -5, sens 50, 9 1/2" air test on quarter. SL all metal thresh -9, sens 35, proper ID on quarter at 11". HH, George (MN)

 

[limegoldconvertible68]

I always thought the proper threshold setting was we you get a steady hum. No matter how high I set the threshold on my F70 there is no hum. At high settings I usually get a lot of erratic chatter and the ID numbers start flashing wildly. Is that normal? Its usually is worse in town so I assume that is the dreaded EMI that I hear about. Sometimes out in the country areas I can run the threshold at 8 or 9 and have a completely quiet machine.

 

[Jeffro]

I always thought the proper threshold setting was we you get a steady hum. No matter how high I set the threshold on my F70 there is no hum. At high settings I usually get a lot of erratic chatter and the ID numbers start flashing wildly. Is that normal? Its usually is worse in town so I assume that is the dreaded EMI that I hear about. Sometimes out in the country areas I can run the threshold at 8 or 9 and have a completely quiet machine.

Try setting it in all metal mode, if you have such a beast. I don't know the machine, but I do know threshold is used on older gold machines. It may be that your threshold is only for all metal mode, and it should be set at a constant for coins. threshold is normally set where you can BARELY hear the humm when you are nuggetshooting. Try the owners manual again.... Just a suggestion.

 

[Streak!]

absolutely!!

unlike the F75..the threshold on the F70 works in Disc mode. The threshold on the F75 only affects the Autotune mode. (All metal side of the screen)
Think of it as just another sensitivity setting...to be used in conjunction with the gain. Higher threshold settings amplify deep signals and tiny conductors, but will make the audio a nightmare in trashy sites. As you can see by the chart George posted you can get similar depth results balancing the gain and threshold, and also deal with any problem areas. Low threshold/high gain will probaly net you large deep conductors, while making the tiny conductors not so bothersome......and low sens/high threshold settings will make shallow low conductors pop..but will probable cost you real deep silver.
When you do the tests George did with only one type target...it will only give you part of the info...but its still a good test and a good example of how Gain and threshold work together.
And by the way, the F70 is silent search...so no matter how high you set the threshold..............you wont hear it in disc. (much like the F5....which incidentally shares more with the F70 than it does with the F75)
SL mode collects a lot more signal.............so will net you more depth in the right kinds of areas.......but I prefer DE for "most" detecting. Streak!
hope this clears things up for you....... Streak!

 

[limegoldconvertible68]

Streak, I certainly appreciate your appearance on our Fisher board. Your answers are very informative and its obvious you have a lot of experience with the Fisher products. Thanks!