Threshold chatter

Took my brand new GPX 5000 out for the first time yesterday and overall was very impressed. I was using factory default settings (fine gold), Search mode "general", Timings "special", tracking "fixed" and was on "mono" using the standard 11" mono that comes with the detector.

At first I was quite surprised at how quiet and stable the threshold sound was, but later in the day for some reason I was getting what I will call "threshold chatter". Even in the same location as I was detecting first thing in the morning the threshold seemed to be wavering making it hard to pick faint detections. Is it possible that this is an EMI issue, and if so can anyone suggest some best option for minimising it by adjusting a few settings.

Kev

Try adjusting the manual tune by a couple of numbers either way from its current "tuned" position.

Also check that you battery cable connections are tight on both the battery and the control box.

Emi from weather I have found to cause bigger spikes in the threshold.

Hope this helps.

I'm in no way an expert on this kevwr, but when this happens to me, the first thing I do is like Yellow Hornet said, adjust the manual tune. Sometimes I hit the auto tune but the machine doesn't always get it right so then I have to do it manually. Some people say to do this next step last, but after this, if there's still a problem, I put the audio into "quiet" rather than normal. Lastly I'd lower the stabilizer and/or RX gain. You may find that a farmer put on an electric fence in the area or the weather turned bad at anywhere within 100kms of you that was causing you chatter. If the noise was more of a ground rather than air noise (EMI), you could also try switching to enhanced rather than fine gold. Chatter is a pain in the butt but with some fine tuning, you should be able to get rid if all but the worst of it.

Thanks for those suggestions, and interestingly the weather was changing at the time.

This was my first ever attempt at detecting and the GPX5000 was so quiet in the morning I found a tiny shotgun pellet after hearing a signal that could easily have been lost later in the day when the threshold wavered. Must admit I am still getting my head around the advantages and disadvantages of each timing, so enhanced is less effected by EMI? Does this come with a penalty in another area such as sensitivity to fine targets?

Another question if I may... does carrying a mobile phone while detecting cause issues?

No kevwr, I think all timings suffer from EMI. My point was that if the chatter was ground rather than air related, then switching to enhanced may fix the issue but when it's an air problem ie weather, electic fence, overhead power lines, then any timing would feel the effect.
I'm presuming that you're detecting around the golden triangle here in Vic, and as you probably know, we are blessed with some of the most mineralised ground here, so the majority of the time if we want to use a mono coil, we have to use one of the smooth timings, namely fine gold, enhanced or sens smooth. The normal timings are for those lucky buggers up north and for when we want to use a DD coil which quietens down the soil to some degree for us.

As far as the mobile phone is concerned, I carry one and if I am in a well signalled area, it does not bother me at all, but if I am in a weak area and the phone is constantly trying to get reception,and then I have noticed an repetitive audio signal coming through the detector's speakers. This gets pretty annoying and distracting after a while, so I either switch the phone off or put it in "aeroplane" mode. So in answer to your question, any metal near the coil is no good, but when in a well signalled area, I haven't noticed any major problems with carrying it on me.

You should not use your soil timing to deal with emi chatter if you can avoid it as this comes at a great cost.
The soil timing is used to cancel out the ground signal, which has little to do with emi however some soil types can amplify the emi's effect.
Or to target a specific type of target.

You should be using the auto or manual tune, stabilizer, gain and audio settings to deal with emi and keep your soil timing in the best one for the soil you are operating in or the one most appropriate for the size targets you are chasing (small shallow gold or large deep gold).

Of the timings I have found that 'finegold' is the noisiest, this is because it is more open on the fast time-constant side of the RX, and the emi chatter is generally a fast time constant signal.

I think this is why inexperienced users and even some more experienced users believe the 5000 to be noisier than the 4500, but if ya whack the 5000 in enhance and compare them you will find this is not the case.

To check this lift your coil off the ground and change from say 'finegold' to normal you will notice that normal is much quieter on the emi front, because it is not as open on the fast time-constant side of the RX.