another mile stone

[wingizzmo]

Well went to the town manager in the next town over from me and asked if I could md the old town hall 1769 . Its used for storage since last year they built a big new one down the street, at first she did not know what to say she asked well what do you do with the stuff you find ? I said well I keep the stuff I find it's a lot of time spent and the cost of the detector she said oh OK but if you find anything historical could you at least show me ! I said sure so off I went got there could not get my v3i to shut up was all over the place dropped the Rx to 1 disc to 75 still way too much emi . Will have to save it for another day so went back to the park I found the large cent yesterday and got my first merc 1925 so another mile stone for me ! Now on to the big stuff hopefully . That brings me to ask how can I control the emi I need to calm this thing down so I can detect the town hall ? There are 2 transformers on telephone poles on both corners of the building

 

[Rob (IL)]

Try 5 band for the filter, frequency offset, and if you have to lower the RX. You could also try the 9.5 instead of the D2.

If discrimination sensitivity is set too high, you will notice erratic behavior when the detector's coil is held at waist level. When the RX gain is set too high, you usually will not have erratic behavior while holding the detector with the coil at waist level, but you will get false readings when the coil is swept over the ground.

The rule of thumb is that, to gain another inch of depth the gain must be doubled. This means that increasing the gain from 14 to 15 will not improve depth much at all whereas increasing the gain from 2 to 4 should gain another inch. So 4 to 8 gains another inch and 8 to 16, oops no 16, another inch. So don't get crazy on setting the RX at the upper levels because it provides diminishing rewards. In some cases the added noise will actually negate the increase. So in my opinion, higher RX and more noise and signal loss would be about the same as lower RX with less signal loss. The bottom line is, with any coil, run the gain as high as you can for stable operation, just as you'd do with any detector. Rob

 

[nw1886]

I've yet to get into EMI where I couldn't run RX 6 or 7 at least. (This may be that my time is short and not getting to more diverse situations though.) But.....even though I've said that, I do know them to be tough spots and was just on the edge with the plain V3.

Don't mean to hijack but, I've been under transformers, heavy rats nests of old power lines and around those junction transformers. Where are the worst places (besides those dog fence and electric fence spots) you've all found?

I'm going to make it a point to go into Seattle and do some "known" nasty spots (just to see). This one spot had I think every EMI source known to mankind and my DFX would still Tone ID me through the noise fine. (Not fun audio wise but.....plenty of stuff found anyways.)

 

[wingizzmo]

For me it would not shut up had it about three feet off the ground vdi,s jumping everywhere blips bleeps Rx 1 disc down all the way to 70, blurp bleep fart noise would not stop talked to a friend of mine last night he works for the electric co. if there were a bad transformer in the area not bad as in not working but bad as in emi leakage you could be 200 ft away and still get emi he said sometimes they get calls to replace them for it because of radio interference for small aircraft another is cable TV line that leak and do the same . I guess when I have time and money I will have to try a smaller coil I still have not sent the unit in for the i upgrade would like to wait till the snow flys and the ground freezes here before I do !

 

[nw1886]

Have never even thought about there being "leaking" EMI from old equipment. (Stands to reason.....) One thing wing, get a V rated coil when the time comes. I was using a DFX set of coils (as accessories) and didn't know what I was missing in stability until a problem spot. Switched up and huge improvement.