Doing some testing last night, I learned a few things and made a new program to go along with this. It was only air testing (the test garden is a long way from maturity) but it's something that I should have done long ago.
1. Max depth is with rx=0 and silencer=-1. I don't think that anyone would be surprised by this. What did surprise me was that adjusting rx to 1 or 2 and/or silencer up to 2 only decreased depth by an inch or two; the difference between rx=1 or 2 was insignificant, and a point or three of silencer didn't make much of a difference either. Silencer = 3 screwed up the tones badly. Rx=3 cut depth dramatically, like four inches.
2. Disc doesn't make as much difference as I'd thought it would. Cranking disc to 10 made no real noticeable difference in depth. I didn't test higher than that. In the interests of full disclosure, I still keep mine at 1...just because.
3. Dropping sensitivity from 90 to 85 cost about an inch. I won't personally run sense under 85, so I didn't test that further.
4. 4 kHz and 8 kHz went deepest, with 12 kHz right on their tail. I was thoroughly unimpressed with the depth of 18kHz, but that's a specialized tool for a very specific job.
5. 4 kHz hit my 3 gm gold ring, my silvers, and all of my junk rings extremely well. It wouldn't reliably hit my 0.8 gm gold ring. It also doesn't like nickels at all - maybe 5" or so, with a must-dig signal at possibly 3". 8 kHz liked it all.
6. Notch had no effect at all on depth, as I'd suspected.
I'd already seen in the field that 4kHz addresses a common complain for the Deus - that it hits hard on aluminum. It will still hit hard on flattened beer cans, but those are easy enough to spot. Perhaps my favorite thing about this frequency is that ever since I started using it, I don't remember digging up a single piece of can slaw...it just goes right over that, and even the foil balls. I'm personally willing to give up some very small gold for this. As others have also noted, it tends to rat out bottlecaps as well.
I'm leaving my low notch at 0-35, but I'm also adding a high notch from 94-99. This will safely let in silver in 4kHz (and even 8kHz, should I find it necessary to change up a band) but should cut out at least some of the ferrous wraparound. I'm finding that now that I've licked aluminum, rusty iron is what's giving me headaches. During air testing, this combination did extremely well, ignoring various rusty chunks of iron from my crap box, new folding knives, and other steel odds and ends that were laying around, but still picked up coins, jewelry (both real and costume), and even the toy cars that I've dug. This may be the one, but field testing will be required. I have high hopes for this. If I can find that hypothetical mix of settings that allows in 90% of what I want and rejects 90% of what I don't want, I'll be a happy detectorist.
What I'm looking at is a general purpose program using rx=2 and silencer=2, with the option to turn both of those down all the way if there's no trash and I need another two inches or so. As much as I've heard about 4kHz's problems with EMI, it's actually the quietest frequency in town here, so I intend to stick with it unless I absolutely must change, and then I'll use 8kHz with all of the other settings remaining the same.
Hopefully I'll get a chance to run this during the week. I've got just the spot to test it out in.
