I went down to the beach to play around and try to learn my CTX a little more. I started off in manual and was able to run the machine at 18 which is the highest I can run it without so much chatter or falsing and totally stable at 17 then I switched to auto +3 and the machine ran at 21 but was super quite. I ran a test with a gold ring and I found that even though the auto sensitivity was running higherat 21 and super stable, manual sensitivity at 17 give me about 2 inches more depth on the ring... ?
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manual vs auto +3 finding
- Thread starter h.m.scoop
- Start date
Jason in Enid
Active member
There are multiple channels the detector listens to. In auto, it picks the quietest one, in manual it uses all 3.
Jason in Enid said:
You are correct in that there are three internal channels. However, in Manual Sensitivity, all three channels are set to the same value. In Auto Sensitivity, the CTX continually measures the magnetic ground interference affecting these channels and adjusts the level of Sensitivity individually for each channel. It does this in an effort to provide the most stable TID.
Choc-Minelab
Member
Digger,
Can you provide information about the three channels. What frequency is each operating at when in Auto mode. Does each channel favor particular targets, or depth? Thanks Kurt
Can you provide information about the three channels. What frequency is each operating at when in Auto mode. Does each channel favor particular targets, or depth? Thanks Kurt
EtracTom-AdirondacksNY
New member
It's not three frequency's it's 3 channels and it compares the signals of these channels (low,medium,high) which could be a conglomerate of the frequencies (these machines start at 1.5khz and go up to 100khz on the frequency scale in I think 1.5khz segments) to the ground it's reading under the coil and I also think the noise cancel channel it's running at has something to do with it too maybe because that is frequency related and it sets the 3 channels to a perceived smooth running amount per the internal computer.
Manual makes it run all three channels at the same FULL amount you've set forcing it to overcompensate. In auto it may pick the medium or lowest one or the highest one to run at at that moment depending on the ground it's reading and EMI due to the noise channel selections as you go along so it automatically moves it for you up or down as capable.
+3 makes it run 3 amounts higher whatever that is it maybe 3 numbers like from normal 17 to 21 forcing it to run hotter.
Manual makes it run all three channels at the same FULL amount you've set forcing it to overcompensate. In auto it may pick the medium or lowest one or the highest one to run at at that moment depending on the ground it's reading and EMI due to the noise channel selections as you go along so it automatically moves it for you up or down as capable.
+3 makes it run 3 amounts higher whatever that is it maybe 3 numbers like from normal 17 to 21 forcing it to run hotter.
Southwind
Well-known member
While I'll be the first to say there are few that can match the E-Trac on silver and copper, but, I can't see the claim of 100 kHz being a real used frequency. I'd be surprised if it uses any frequencies above 12 kHz except as harmonics not analyzed. The reason I say this is at 100 KhZ a detector should kill on supper small gold. It doesn't even come close. It does act like a detector using 10-12 kHz.
Just like everything else there is a time and place for most settings. The same goes for Manual vs Auto +3. I've tested targets where they sounded great in Auto +3 and like crap in Manual 28 and targets that sounded great in manual 28 but like crap in Auto +3.
Just like everything else there is a time and place for most settings. The same goes for Manual vs Auto +3. I've tested targets where they sounded great in Auto +3 and like crap in Manual 28 and targets that sounded great in manual 28 but like crap in Auto +3.
always thought that FBS is best run stable, when I switch to manual at say spot X and use manual to the same number that auto plus 3 is giving me its never as stable, so always run auto plus 3 on most sites, maybe running on the raggered edge is fun 
as in turning it right up.
but most places I don't want raggered edge detecting and neither does my head
come home with a headache.
AJ
as in turning it right up.but most places I don't want raggered edge detecting and neither does my head
come home with a headache.AJ
EtracTom-AdirondacksNY
New member
I may be wrong about the 100 kHz high but I'm pretty sure I read it here or somewhere early on and what the noise channel selection does is pick a group of these numbers to use like some claim that lower noise channel selectionnumbers hit better on one thing like coins and higher noise selection channels hit better for the other like jewelry.
It starts at 1.5khz and the numbers within that channel go up in increasing spacing of these increments of 1.5khz I believe and the next channel starts at 3khz and the numbers are different in that noise channel and they get spaced further apart in that channel selection from the lowest to highest starting and ending higher for each noise channel. The machine sends these out into the soil and scans for the best response from these number groupings to make it's analytical determination on the target. My machine sets the noise channel at either 6, 9, 10, and 11 most all the time here when I do a noise cancel. I've never gotten lower than a 6. Someone I read on here experimented with the different channels and found that I think it was the lower numbered one like 2 hit coins better in his conditions and the higher one like 11 was better for jewelry. I may have that backwards but think I'm right. Try doing a search in the ETRAC category and see what comes up.
It starts at 1.5khz and the numbers within that channel go up in increasing spacing of these increments of 1.5khz I believe and the next channel starts at 3khz and the numbers are different in that noise channel and they get spaced further apart in that channel selection from the lowest to highest starting and ending higher for each noise channel. The machine sends these out into the soil and scans for the best response from these number groupings to make it's analytical determination on the target. My machine sets the noise channel at either 6, 9, 10, and 11 most all the time here when I do a noise cancel. I've never gotten lower than a 6. Someone I read on here experimented with the different channels and found that I think it was the lower numbered one like 2 hit coins better in his conditions and the higher one like 11 was better for jewelry. I may have that backwards but think I'm right. Try doing a search in the ETRAC category and see what comes up.
Southwind
Well-known member
Same here. I've tried many times running in manual and all it does is cause me to dig more false rusted iron signals. Some people may have much cleaner sites but with my site the rusted iron is 10-12" or more and sounds and reads just like a coin at that depth. I put it on Auto +3 and get a lot less false signals and switch to manual if I want to check an iffy out a little.
Minelab protects their FBS like Hillary and email LOL. I know they claim to go up to 100 kHz but I just don't see it in practice. I can easily tell a 6.9 kHz machine from a 18 kHz when it comes to gold. At 100 kHz the E-Trac should plain kill the other machines on small gold and it does come close.
Don't confuse channels with frequency. The purpose of the three channels is to implement the optimum frequencies for low conductive targets, mid-conductive targets and high conductive targets, all of which are being processed simultaneously. Using multi-period rectangular waves, the CTX can transmit 28 frequencies and recognize the "best" frequency within each channel, for the three conductivity levels. As I've mentioned in the past, using manual Sensitivity locks all three channels to the same sensitivity level. Auto Sensitivity allows the detector to set the level for each channel in an effort to maximize the performance over varying degrees of ground interference. JMHO HH Randy
Johnnyanglo
Active member
The FBS transmits many harmonic frequencies, far more than 28. It only captures the 3.125kHz and 25.0kHz, which are the primary and the 8th harmonic. Any other ideas about 100kHz freqs are just marketing hype. The 25kHz isn't particularly strong amplitude so it doesn't help the detector with those weak conductors particularly well (like thin jewelry), which is where the FBS falls down.
Noise Cancel: The detector can adjust from the above frequencies by 10%.Thus, the high freq of 25 kHz would be pushed to 27.89 kHz if Channel 11 were used, or dropped to 22.2 kHz if Channel 1 were used. Similar percentage change for the low freq.
The difference between 22.2 and 27.89 kHz is minor and isn't likely to change the detectability of targets. It was meant to reduce external signal noise. I let the machine find the best channel - forcing one on it may reduce sensitivity and you wouldn't even know it.
Johnnyanglo
Noise Cancel: The detector can adjust from the above frequencies by 10%.Thus, the high freq of 25 kHz would be pushed to 27.89 kHz if Channel 11 were used, or dropped to 22.2 kHz if Channel 1 were used. Similar percentage change for the low freq.
The difference between 22.2 and 27.89 kHz is minor and isn't likely to change the detectability of targets. It was meant to reduce external signal noise. I let the machine find the best channel - forcing one on it may reduce sensitivity and you wouldn't even know it.
Johnnyanglo
MINELABBOB
New member
yes its not a small gold killer so it makes me think it does not stay on the high side khz to long but 4 avg.size gold and above i have found wedding bands 2-3grams
6-7 in. in mild soil. so i guess that is good even a sm.gold within 5in. was no problem. my old mxt-pro with a 5in coil would kill sm. gold chan
6-7 in. in mild soil. so i guess that is good even a sm.gold within 5in. was no problem. my old mxt-pro with a 5in coil would kill sm. gold chan
electricmetal21
New member
While we're on the subject of sensitivity. I've got a question.
When the CTX is in auto sensitivity, there are two sensitivity numbers shown on the sensitivity panel on the detect screen. The green number on the right of the sensitivity panel is the suggested sensitivity that the CTX calculates and suggests using and, the white number on the left of the sensitivity panel is the sensitivity value that the CTX is currently using.
That said, why is it that when the CTX is in auto sensitivity, these two numbers don't usually match each other? You'd think that the CTX would always be setting the white sensitivity number on the left (the number its using) to the green number on the right (the suggested sensitivity number that it calculates and suggests using).
Don't know if this this question has been answered before on the forum.
Thanks
When the CTX is in auto sensitivity, there are two sensitivity numbers shown on the sensitivity panel on the detect screen. The green number on the right of the sensitivity panel is the suggested sensitivity that the CTX calculates and suggests using and, the white number on the left of the sensitivity panel is the sensitivity value that the CTX is currently using.
That said, why is it that when the CTX is in auto sensitivity, these two numbers don't usually match each other? You'd think that the CTX would always be setting the white sensitivity number on the left (the number its using) to the green number on the right (the suggested sensitivity number that it calculates and suggests using).
Don't know if this this question has been answered before on the forum.
Thanks
MINELABBOB
New member
i think to answer your question, it is setting a VALUE another words it is setting a SENCE that it feels can handle the GROUND CONDITIONS
WEN I START OUT IN AUTO+ IT TELLS ME HOW GOOD OR BAD THE GROUND IS. with this being said i can now set my manual sence
to the no# that is around what auto+ was or higher!!! if my auto + showed 23-17 i will set manual at 23 or higher if conditions allow. the key
here is CONDITIONS ALLOW!!!!!!!!!!!!! if super trashy i run in auto+
MINELABBOB
WEN I START OUT IN AUTO+ IT TELLS ME HOW GOOD OR BAD THE GROUND IS. with this being said i can now set my manual sence
to the no# that is around what auto+ was or higher!!! if my auto + showed 23-17 i will set manual at 23 or higher if conditions allow. the key
here is CONDITIONS ALLOW!!!!!!!!!!!!! if super trashy i run in auto+
MINELABBOB