By Steve Herschbach
First off, I want to point out that what I am about to describe is not uncommon with high power detectors that have a coil that can be disconnected. The only way to really eliminate the problem is to hard wire the coil, which is another reason for why this option is chosen by so many manufacturers of underwater metal detectors. The White's TDI Beachhunter is a good example. The problem has its root in coil capacitance and the high voltages involved, and the difficulty of getting good shielding using a removable connector.
If the Impulse AQ is submerged halfway, so that the water level is anywhere in roughly the area indicated in the photo below, you will get continuous false signals. Just holding the unit stationary in the water at this level will cause signals as the water moves around the connection area. If you are not aware of what is happening it is every easy to mistake this for electromagnetic interference (EMI).
The problem is worst in the Tones mode, which I just happen to be using a lot. It is accentuated by a short pulse delay, high sensitivity settings, and low ATS settings. If you want to reduce the false signals, here are some solutions:
Use the All Metal or Volcanic modes instead of Tones Increase the Pulse Delay to 9 or higher Reduce the Sensitivity to 4 or lower Increase the ATS to 8 or above Or some combination of the above.
In practice this only occurs when wading, and only at a certain depth. My solution was simply to stay either deeper or shallower. This does leave a strip or area unhunted. You can either switch the settings as suggested above, or do something to change the height. Like hunt that strip with mask and snorkel, for instance.
Anyway, hopefully this is put in the manual as it is something inherent in the operation of the detector, and can drive you nuts if you run into it and do not know what is going on. It took me several hours of detecting to put two and two together, and it was then confirmed that yes, that is the way it is.
By Joe Beechnut OBN
Early on I see the Halo of targets in the threshold of the "AQ" doing airtest..... so I've been playing with the settings to see if I can pull up more of the audio of them when out hunting in the water. Jim and I have hunted together before, a very good "old beach" hunter.
Video of those changes in the threshold Jim speaks of....
By Steve Herschbach
Here are my latest digs in the water at Tahoe. Things were going great until the handle on my old scoop finally gave up the ghost. Can't complain, it served me well, but not like you just run to the store and get another. I'll have to make one.
Anyway, I have to admit at this point I am wondering where my first gold ring with the Impulse is at. Popular beach, tons of people in the water for many years, plenty of targets... no ring. Maybe somebody is running a magic detector here that finds gold rings while leaving all the aluminum tabs and nickels behind?
I'm actually very pleased with this mix of trash. Exactly what I expect to be finding, but getting it pretty focused, good ratio of ferrous to non-ferrous. I’m digging tight signals that have a little depth to them. Generally ignoring boomer targets and surface double-blips, though a few surface targets got dug just because they were so easy. It's mostly bottle caps and large ferrous faking me out, but not so much as to bother me. I expect a certain amount. Anyway, I need to get a new handle made up so I can get back in the water tomorrow. Best find - a Buffalo nickel, can't read the date so far. The item in lower left is a corroded zinc penny.
I’m in thick magnetite sands with lots of rock. Hunting tones exclusively, 7uS, sensitivity to max, ATS and reject at preset.
Fisher Impulse - the non-ferrous
Fisher Impulse - the ferrous
Broken scoop handle
By Steve Herschbach
I will be using my Impulse with the battery end well out of the water while shallow wading or on the beach, etc. I wanted to get away from wired phones and save the waterproof phones for when I actually need to submerge the machine. No sense putting any more wear and tear on the cable than I need to.
So I found a source of relatively inexpensive M8 pigtails and cables, AutomationDirect. Never ordered from them before, but it was easy and cables arrived in two days. I got two pigtails for the headphone 5-pin connector, one straight, and one 90 degree. And I ordered a couple longer 4-pin cables for the power connection, to work with a high capacity power pack I have on order. More on that later when it arrives.
I decided to use the 90 degree cable to make an adapter for my new TaoTronics transmitter/receiver box so I can use my Minelab phones, which I like, with all my detectors. There is also a less expensive transmitter only version.
M8 5 pin 90 degree pigtail
I dug through my pile of adapters and found a spare mono 1/8" extension cable and cut it off, saving the female end for this project. The TaoTronics comes with a RCA to 1/8” female cable that would also probably work for this. I hooked up the 90 degree cable and powered up the Impulse. I randomly hooked up the two wires from the 1/8" socket to the five while having some stereo earbuds plugged in, and found that the brown and gray wires gave me audio in both ears. According to the chart below brown is #1 and gray is #5. I wanted to make very sure there was audio in both ears using the mono socket but with stereo phones plugged in, so good to go there.
I cut the cable down short, spliced and covered with shrink tube, and wrapped a little electrical tape on to add some beef. Not pretty but it will work - a typical Herschbach job. I bent the cable under the armrest, and added a stick on square of Velcro to back of the TaoTronics transmitter and the leg stand. I'll add more squares to my other detectors so I can move this transmitter around to whatever I am using. A little tie wrap secures things.
Fired it up, paired easily with my Equinox 800 headphones, better audio than the Fisher phones, and frankly the Equinox phones are not the best in that regard. Cheap, super easy... I'm quite pleased with this. I can of course use 1/8" type wired phones or ear buds if I want. I'll make another adapter with the straight connector but go to 1/4" with it, so I can use my Sun Ray Pro Gold headphones without an extra adapter. I'll probably make that cable a little longer than this one, which I wanted as short as possible.
If you got the TaoTronics transmitter only box for $20 and this cable for $8.50... well, this is pretty cheap and easy, and will work with a huge number of headphone options.
Ironically my new Tarsacci MDT 8000 comes with am M8 to 1/8" adapter with one little problem. Fisher uses a 4-pin connector for the power/headphone combo cable, but then for some reason they use a 5-pin M8 for the headphone only connector. The MDT 8000 headphone adapter is of course 4-pin. I swear they must all have secret meetings to make sure nothing from one detector ever works with another.
Click or double click photo for high res version.
AutomationDirect M8 Cable Specs pdf