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coil wire length
- Thread starter z8chase
- Start date
I did a 8 inch coinsearch coil back a few years ago and felt it ran a little smoother and stable on actual in the ground targets and possibly a little more depth, but not 2 inches and maybe 1/2 inch or so. This was on a XS 2 Sovereign I had which I used in a well worked park in a area I worked to death before I cut my cable down. Tried it at this spot 3 days in a row and got silver 2 of the 3 days. Maybe just luck too, but felt it did better for me in other parks too were considered worked out.
Rick
Rick
Terry,interesting observation,that's a big increase.HH Ron
Critterhunter
New member
Maybe, since that coil is using the early version of the pre-amp circuit in the coil, there perhaps is a benefit to a shorter coil cable with it? Maybe it's not making the signal as robust against EMI or signal degradation as it travels up the cable to the machine?
But in terms of a modern Sovereign compatible coil, such as say the 10 or 8" Tornados or the 12x10, I have seen no increase in sensitivity ability or in depth when precisely measured in this pictorial video I did using a ruler in the foreground of the camera to contrast things...
http://youtu.be/1CRxPoJ6O7o
I did this test by testing the depth with and without the Digisearch meter plugged in between the coil and the machine, since this meter adds a good 3 foot or so of coil cable length when it's plugged in.
Also, this test also explored the urban legend that not using a meter would enhance depth, since some Sovereign meters such as the Digisearch don't have their own battery and so derive their power from the TX output power to the coil. In reality the meter and the TX winding are in parallel to each other, so whether the meter is plugged in or not the coil transmit winding still is seeing the same level of voltage.
Still, I wanted to test that out as well, and since both "burdens" of a longer coil cable and a meter load are both being inflicted on the GT at the same time, if either had some measurable impact we should see it in this video.
The truth is that, unlike other machines, the coil cables for the Excalibur and Sovereign are not shielded. Only exception I'm aware of is I think the newer version of the S-12, and far as I heard that was due to them needing shielded cable anyway for building the FBS version of that coil, so I would guess they figured might as well just order the shielded cable and use it for both versions of the coil maybe?
Why aren't BBS coils shielded? Somewhat unique to the Sovereign/Excalibur, they have a pre-amp circuit in the coils to boost the received signal before it has a chance to degrade traveling up the wire or pick up EMI in that trip. By making the very weak signal somewhat more robust, in theory it should withstand these things better as it is routed to the control box. Minelab's own website eludes to this circuit and covers these things for the Sovereign/Excalibur, which I have re-quoted in the above pictorial's video description below it.
Once inside the box, your sensitivity control does further gain on the received signal. EMI or ground mineralization picked up by the coil determines just how high you can raise this second gain on the signal by your adjustment of the sensitivity control.
Now, might there be high EMI situations where a shorter cable might help some, or even a meter plugged in makes EMI worse due to it's internal electronics picking up EMI? Maybe, but I can say that EMI is more of a coil issue and not elsewhere, because the 12x10 makes EMI much less of a factor for me when right around sources of it.
Remember though, Minelab built the Sovereign and the Excalibur to both be hip or chest mountable, which requires longer coil cables and aftermarket coils have this extra length as well so you can do that. I would figure Minelab had more than just one reason for using a pre-amp, to both increase depth, and also for more small target sensitivity in some respects. And #2- So an extra long coil cable wouldn't cause the RX signal to degrade as it made it's way up to the machine, traveling roughly 2 to 3 times the distance or perhaps 4 (with certain meters plugged in) then what would be typical for other detectors.
But in terms of a modern Sovereign compatible coil, such as say the 10 or 8" Tornados or the 12x10, I have seen no increase in sensitivity ability or in depth when precisely measured in this pictorial video I did using a ruler in the foreground of the camera to contrast things...
http://youtu.be/1CRxPoJ6O7o
I did this test by testing the depth with and without the Digisearch meter plugged in between the coil and the machine, since this meter adds a good 3 foot or so of coil cable length when it's plugged in.
Also, this test also explored the urban legend that not using a meter would enhance depth, since some Sovereign meters such as the Digisearch don't have their own battery and so derive their power from the TX output power to the coil. In reality the meter and the TX winding are in parallel to each other, so whether the meter is plugged in or not the coil transmit winding still is seeing the same level of voltage.
Still, I wanted to test that out as well, and since both "burdens" of a longer coil cable and a meter load are both being inflicted on the GT at the same time, if either had some measurable impact we should see it in this video.
The truth is that, unlike other machines, the coil cables for the Excalibur and Sovereign are not shielded. Only exception I'm aware of is I think the newer version of the S-12, and far as I heard that was due to them needing shielded cable anyway for building the FBS version of that coil, so I would guess they figured might as well just order the shielded cable and use it for both versions of the coil maybe?
Why aren't BBS coils shielded? Somewhat unique to the Sovereign/Excalibur, they have a pre-amp circuit in the coils to boost the received signal before it has a chance to degrade traveling up the wire or pick up EMI in that trip. By making the very weak signal somewhat more robust, in theory it should withstand these things better as it is routed to the control box. Minelab's own website eludes to this circuit and covers these things for the Sovereign/Excalibur, which I have re-quoted in the above pictorial's video description below it.
Once inside the box, your sensitivity control does further gain on the received signal. EMI or ground mineralization picked up by the coil determines just how high you can raise this second gain on the signal by your adjustment of the sensitivity control.
Now, might there be high EMI situations where a shorter cable might help some, or even a meter plugged in makes EMI worse due to it's internal electronics picking up EMI? Maybe, but I can say that EMI is more of a coil issue and not elsewhere, because the 12x10 makes EMI much less of a factor for me when right around sources of it.
Remember though, Minelab built the Sovereign and the Excalibur to both be hip or chest mountable, which requires longer coil cables and aftermarket coils have this extra length as well so you can do that. I would figure Minelab had more than just one reason for using a pre-amp, to both increase depth, and also for more small target sensitivity in some respects. And #2- So an extra long coil cable wouldn't cause the RX signal to degrade as it made it's way up to the machine, traveling roughly 2 to 3 times the distance or perhaps 4 (with certain meters plugged in) then what would be typical for other detectors.