Question about filters 1 & 2 in GoldQuest SS V2

[GeoMax]

Hello together...

Below I have some questions about filters 1 and 2 in GoldQuest SS V2.

Eric Foster built the GoldQuest detector in various versions over several years. There was the GoldQuest, GoldQuest SS, GoldQuest SS V2, and GoldQuest V3.
Compared to its predecessor (GoldQuest SS), the GoldQuest SS V2 features an additional filter 1 & 2 functionality.
Reg Sniff once commented on these filters 1 & 2 as follows.
“… The GQ and the GQ V2 are again, almost the same except for the addition of a second filter and maybe the changing of the coil connector. Again, the controls are fundamentally the same.”

And that this dual filter is supposed to suppress interfering ground signals.
“… and the dual filter to minimize bad ground signals.”


Image of a GoldQuest SS-V2 detector

Now my questions.
1) Which "bad ground signals" are suppressed by these filters 1 & 2?
2) What signal frequencies are suppressed?
3) What might such a two-stage/dual filter circuit look like?
4) How does it work together with the S.A.T. function?

Any ideas? Thank you in advance for your input/help.

[GeoMax]

Does anyone has an info update on my questions?

[Carl-NC]

Sorry, I have no schematic for this. Probably the "filters" refer to high-pass filters which would help suppress slow ground signals. In the Gold Scan design there are 2 HPF sections; one is the SAT stage after the demods, the other is after the summation amp.

[Detectorist#1]

Hi GeoMax,
Are you sure that this is GoldScan SS V2 picture? I have picture of GS SS V2 from one guy from NZ. Hi sold this type of MD and hi attached the picture. In this picture no switch for "Filter 1 or 2" choice. Attached is this picture. Unfortunately this not answer for your question for the real function (difference in the settings) of this switch.

[kt315]

Does anyone has an info update on my questions?

hello GM

can you measure your coil inductivity? must know.

[GeoMax]

Hi GeoMax,
Are you sure that this is GoldScan SS V2 picture? I have picture of GS SS V2 from one guy from NZ. Hi sold this type of MD and hi attached the picture. In this picture no switch for "Filter 1 or 2" choice. Attached is this picture. Unfortunately this not answer for your question for the real function (difference in the settings) of this switch.

Hi,

Yes, it's confirmed: GoldQuest SS V2. I checked my pictures. It seems that Eric probably built two different versions of the GoldQuest SS V2. One with Filter 1& 2 and one without these Filters. While checking my pictures, I also found two different versions of the GoldQuest SS. The GoldQuest SS Version 3 looks completely different from the case, but also has these filters 1 & 2.

[GeoMax]

hello GM

can you measure your coil inductivity? must know.

I do not know the inductivity of this detector (coil) from the image I posted. I have it from the Internet.

[Carl-NC]

can you measure your coil inductivity? must know.

My GoldQuest coil is 199uH and 3.22Ω. I have an SS with no version number, and no filter control.

[GeoMax]

I measured the Eric Foster coils which I have here.

GoldQuest SS Coil 11 Inch
L=332,4uH @ 1kHz
R=5,8 Ohm

Sandpiper1 Coil 8 Inch
1005uH @ 1kHz
R=8,9 Ohm

BeachScan Coil 11 Inch
L= 318,5uH @ 1kHz
R= 4,33 Ohm

My Sandpiper1 PI works also very well with the BeachScan 11 Inch coil.

[kt315]

thank you, guys. I suspected it is the same as Goldquest Aquasearch, but not.

[kt315]

you can raise up any Eric's posts, from a start to the finish, i do not see a problem for you. Eric wrote sometime Goldquest SS is 'experimental' one.

FIVE MICROSECONDS at the BEACH


Posted by: Eric Foster (---.proxy.aol.com)
Date: March 18, 2005 05:44PM


In fact, I was there for rather longer than that, in spite of the weather not being as warm as forecast. My purpose was to see if one could use even shorter delays on wet sand and even in the water’s edge. Recently, I have developed some new coil technology and associated electronics which makes it relatively easy to sample as early as 5uS. In fact I have almost a uS in hand, at the end of the damping period, but I didn’t want to be working “on the edge”, as it were.
All this started when a nugget hunter sent me some “invisible nuggets”. In other words, no other PI nugget detector would find them, even if they were rubbed on the coil surface. One unit, of course, which would detect them OK, is the Fisher Goldbug 2 high frequency IB detector. So why would a beach hunter want more sensitivity to smaller and poorly conducting objects? One reason is gold chains. Many of these have small, fine, links and the majority of PI’s miss them, unless they are still attached to a pendant, or larger metal object of some sort. Then there are ear rings, small toe rings and other tiny items of jewellery. Also, shorter sampling delays could mean more signal and range on normal size gold rings, particularly on those of lower carat values. The big problem is, of course, the conductive sand and seawater and the large background signals that these would produce.
The unit that I took to the beach was a test bed special, consisting of a belt mounted control box and the electronics running off 8AA alkaline batteries. Although in a slightly larger box, it has the appearance of an overgrown Goldquest SS, in fact the controls are the same, except for a receiver amplification control. The coils I took were 11in diameter and 8in diameter mono coils, the same in appearance as my normal monos. These were connected by standard length of 2.125m of cable to the control box.
Two important features are the calibrated delay control, which can be set in 1uS steps from 5uS to 15uS. This gives the full range of delays which I normally use on the beach. The other feature was an analogue meter that could be plugged in to gauge the strength of the beach/water conductivity signal at the output of the integrator. Other standard features, as on the Goldquest SS, are the SAT control and two stage filter.
The tide was out at the local beach, so straight down to the water’s edge; detector strapped on and an 11in coil fitted on the shaft. No point in being discouraged straight away, so I set the delay at the 10uS point, where I knew it would be useable. So far, so good, with the coil dipping in and out of the water, and one or two pulltab targets that showed the detector was working. O.K., let’s crank it up to 5uS and see what happens. Nothing major, just a bit more variation in threshold as the water sucked in and out over the coil. Back away from the water’s edge, but still on very wet sand, I did some more detailed tests. The coil was more height conscious, but switching in the second filter to give a fast SAT, overcame the problem, and I was able to sweep normally. There was a very noticeable difference in “bouncing “ the coil vertically over the sand at different delays. At 15uS, there was little response. At 10uS, there was a medium response, and at 5uS the response was quite strong. This is exactly what I would expect as the delay was shortened over a seawater saturated beach.
Next, I plugged in the meter to look at the integrator signal. This is a point before the d.c. amplifier and SAT circuit, and the signal here would give an indication as to how much dynamic range was left, before the circuits saturated from too much background signal. I had set a target of 2V, which is half way to the 4V limit of the circuit used. I was surprised to see that with the 11in coil sitting on the wet sand, the signal was less that 0.1V at the 5uS delay. No problems here.
Time for some serious searching. Just one thing bothered me a little. Every so often there was a loud bong in the audio which always seemed to occur when I was moving. Anyhow I kept going and dug up a brass Pet Plan tag which a dog walker had lost. I then buried a thin 22C gold ring (tethered to a line of course) and did some tests at the different delays. 5uS seemed to give the best signal, although the occasional bong still happened. Turning my attention to this, I found that if I rapped the control box, it would give this spurious audio signal. The coil connector was tight, so it must be something loose inside. Not having thought to bring a screwdriver, I considered it best to return to the workshop and investigate.
A few minutes after the lid was off, the cause became apparent. A less than good grounding contact on one of the shielding plates. Grounding and shielding of the electronics has to be good, and all connections tight both mechanically and electrically, when running at these short delays and wide amplifier bandwidths.
So, there is always another day. I haven’t yet tried the 8in coil, although as the 11in one worked fine, I don’t anticipate any problems. I want to try a stony patch and the dry sand too. By the way, it does detect the “invisible” nuggets at 2 – 3in, which I am pleased about.
Eric.

[GeoMax]

Hi KT315,

thanks for posting Eric's old forum posts about the GoldQuest. I am curious, where can you find such old posts?

[kt315]

Technology Forum | Find's Treasure Forums (findmall.com)
former PI Tech Forum of Eric

[Detectorist#1]

Hi KT315,
This additional information from the post of Eric is useful, but some questions rest. I guess that two stage filter is situated as the feedback from output of the SAT stage to the input of the SAT stage ( as controlled resistance (maybe J113) connected in parallel to the input resistor (connected to GND)). The parameters of those two stage filter determine how fast is SAT function. Eric mention "but switching in the second filter to give a fast SAT, overcame the problem". It is interesting what is the scheme of those two stage filter and how the switching in the second stage of filter gives more fast SAT. Maybe some owner of GQ SS V2 with filter's switch will be capable to draw the schematic for us (for not to inventing the wheel again).

[Altra]

I repaired a GoldQuest for a guy years ago and found it was the same as the CS6 PI. Eric also designed the CS6. The only exception the GQ had a battery low circuit. The one I repaired did not have the filter switch. You can see the CS6 schematic here post #15

https://www.geotech1.com/forums/foru...ics/5916-cs6pi