Fisher Gold Bug

[ivconic]

Ususally I try to use low hFE transistors for low distortion on the Tx, if I find, had good results with less than 170 hFE. But what about crystal driven oscillators, what transistor have you got on you Gold Bug pcb for the TX?

I am stuck at last opamp before the audio stage.
The threshold part.
It is having very weak signal at the output. Not capable to drive audio.
Also have found several mistakes, not mine, from original schematic.
Everything up to that last opamp i trimmed to work just nice.
It is dual. One half is alright, another half is having problems.
Configured badly. Not by me.
So ... lot of labor is waiting me yet.

[ivconic]

I hope you made advances in your project, Im very interested in your progress. I have made a quartz oscillator as it's on the Gold Bug schematic you posted, installed it to one of my non working pcb and it's alive! Kicks 30 cm on a 1euro coin easily .
The oscillator works on +5 volt and I has 10Vpp on Tx, so basically double of the supply voltage. With my transistor oscillators I could not make double voltage of the powersupply without distortion, this quartz oscillator is usefull I like it. Also would like to try the phase shifter with CD4013.

Best regadrs to you!

Always put 1M resistor parallel to crystal. So as i noticed; sometimes 4060 will not work without it.
Also since you used that part and it works for you; you shall use also TX output as original, with one transistor and trimmer to adjust amplitude.
It is better solution than the "alternative" i put also on schematic.
At my board supply is from two Lipo 18650 wired in series, middle point is GND.
Rails are +/-3.8v. TX supplied with bit less than 8v. And TX amplitude is 16Vpp.
Cleanest possible sinus that you can see.
TX out works only when coil is attached. Without coil the transistor is closed.

[Nandor]

I also use the CD4060 to drive the crystal. Last year I tried it so hard and without succes but now I know that the amplitude from CD4060 needs to be trimmed. It works just fine with the TGSL coil 10.5Vpp from +5 volts, pretty clean. My o-scope is a Hantek DSO5202P it's a decent one, had succes with it bringing to life many failed projects before I had it.

What about the Q of the coil, Less Q is better for forced driven coils right? Seen some Fisher coils on eBay.
I wish I could give you tips have a great time doing the Fisher Gold Bug!

regadrs

[Prospekteur]

Im also interested in this project. Is there a working PCB-Layout available? Some say its working and others have errors;-).

[ivconic]

I also use the CD4060 to drive the crystal. Last year I tried it so hard and without succes but now I know that the amplitude from CD4060 needs to be trimmed. It works just fine with the TGSL coil 10.5Vpp from +5 volts, pretty clean. My o-scope is a Hantek DSO5202P it's a decent one, had succes with it bringing to life many failed projects before I had it.
What about the Q of the coil, Less Q is better for forced driven coils right? Seen some Fisher coils on eBay.
I wish I could give you tips have a great time doing the Fisher Gold Bug!
regadrs

Obviously the schematic that flows around for years; consist some mistakes.
I can't count them yet, until i make working devices.
Above those i made additional mistakes when drawing pcb.
Would be great to find original Gold Bug on Ebay by affordable price.
Coil for Gold Bug differs a lot from all other Fisher coils.

[ivconic]

Im also interested in this project. Is there a working PCB-Layout available? Some say its working and others have errors;-).

I haven't posted my pcb and it is good thing, because of the mistakes i am discovering now.
Any other pcb, drawn by other people? I can't tell. So far i didn't see neither one for Gold Bug.
If you have link to someone else's work; please post here.

[Prospekteur]

Ok...Thanks Ivconic;-)

[ivconic]

I discovered more mistake and discrepancies on "original" schematic.
So i am giving up from this by now. Because i have several parallel works that are waiting on the bench.
So far with present information that we have; Gold Bug attempt is pure waste of time.
So today i decided to give up by now. Until i get new more accurate information.

[Prospekteur]

"So i am giving up from this by now. Because i have several parallel works that are waiting on the bench."

I know that. Im wondering since a while how you manage it, to work on several projects at the same time;-).

So my last question is: Is there another PCB Layout for a high frequency unit with discrimination available ?

[ivconic]

"So i am giving up from this by now. Because i have several parallel works that are waiting on the bench."

I know that. Im wondering since a while how you manage it, to work on several projects at the same time;-).

So my last question is: Is there another PCB Layout for a high frequency unit with discrimination available ?

I don't know about Gold Bug.
Maybe Tesoro Lobo.
KT315 posted links many times on forum.
...
I don't give up only because of other projects that are waiting on the bench.
Mostly i give up because "original" schematic consist many errors.
I will look up forward to obtain either Gold Bug detector... either more accurate documentation if such exists among colleagues.

[dbanner]

I applaud you for your efforts.
I'm going to scrutinize the schematic for errors in the area of the channels. I'll run some simulations and post them.

Whatever errors are on original schematic will be found!

[dbanner]

That CZ-6 pre-amp WILL have a noticeable phase/gain behaviour, it's mostly defined by the R's and C's in the feedback network.
The 1K0 & 4n7 pair give a low-pass roll-off at f_c = 34 kHz , and the high-pass roll-off, determined by the 47R & 1u0 pair, give an f_c = 3.4 kHz.
There may be some additional contributions from the input filter ( the 47R + 47R etc low-pass filter circuit ), and the 200pF stability cap will affect things at high freqs, I don't know what, though.

Thanks for the info. Nice circuit.

[dbanner]

I wonder why they didn't just use an opamp chip instead for the RX front end, performance? Price?

[kt315]

I wonder why they didn't just use an opamp chip instead for the RX front end, performance? Price?

noise factor.

[dbanner]

Ok.

I found that some component values look quite wrong on lahr's schematic. Up to the ground balance pot the circuit is flowing nicely, so long as the component values are corrected and the offsets are correctly trimmed, the circuit should work fine up to this point.
After that seems where there are even more errors.
Will keep at it.
BTW, Ivca, have a look at the Troy shadow X5 schematic, pretty similar topology around the synchro- demods.