Fisher Gold Bug

[ivconic]

Fisher Gold Bug redrawn.

[ivconic]

I like to "convert" gibberish kind a style of drawing schematics to more clearer one.
It was literally scary to see previous available schematic that circulates over the forums.
You get wrong impression when observe it.
Now is more clearer and easy to analyze it.
No scare anymore from this one!
It would be piece of cake to mod it, modernize it and improve it.

P.S.
Looking at the RX front end... hey dude! I would like to try the dope you were on, while designed it!!!

[liekwang]

Fisher Gold Bug redrawn.
[ATTACH]53222[/ATTACH]

this is what I'm waiting for an idea from the invonic lord I'm waiting for the fcb from the master,

[ivconic]

It wont be any sooner. It is long way from unproven schematic to appropriate pcb and workable device.
Besides, if i dare to try to make it; it will be most probably based on Atmega mcu with lot of mods and changes.
Long way! Long shot!
I just wanted to "decipher" scary gibberish schematic that we had so far.

[Nandor]

Thats a great contribution!
Congratulations for your work.

best regards.

[ivconic]

Thats a great contribution!
Congratulations for your work.

best regards.

Sometimes I kill boredom like that.
And is good to have easier insight in the design.
Cheer!

[ivconic]

So that would be first Gold Bug, working at 19.2kHz.
Gold Bug 2 uses MAX412 at the RX front end, instead "poor man's opamp" solution as in this case.
I am looking up now for the Gold Bug 2 schematic or at least parts of schematic with RX&TX frontends.
I think i saw it somewhere ...

[dom44]

good job ivconic I have been playing with the circuit for a while now, except i moded it i have a lobo front end amp circuit works at 32khz and 4069 crystal driver for the transmit circuit driving at 32khz to experiment I will use your circuit to check against mine to see if i have any mistakes on my circuit. I have also just finished the lobo diablo running 25khz with a 4060 and 3.2768mhz crystal.



this part of the circuit works 100% i have built it.

[kt315]

still one sch from Russia. i think this is Alex Serbin. hybrid.

[ivconic]

I am "contemplating" more wider options now.

[dbanner]

I assume the coil shield is connected to battery negative (ground) on original schematic, with the PS rails at ground and +6V, the virtual common being at 2.5V.......there is something strange about this, the entire circuit is always above ground throughout all its transients, perhaps someone has the pin out and schematic for the coil.
I wonder if perhaps a more conventional bipolar power supply with +5V and -5V and battery minus serving as ground as well for shield ground.
I noticed fisher labs using this unconventional and strange power supply topology since the start of their Mscope series beginning with the 1210x. You might say the entire circuit has been level shifted, but why?
I don't like one bit. Unless there is some real benefit in terms of performance, I'd dispense with it in favour of something a little more mundane.
Also, using more mainstream junkbox opamps to replace those not-so-regular ones, shouldn't make much difference to extreme performance.

[ivconic]

I agree with you dbanner.
Few "awkward" (for diyer) moments in all those schematics from that series.
Obsolete components, transformer etc.
But all solvable today.
I am great Fisher fan since '90s.
I had dozen models... except Gold Bug.
Had one, broken from a start. At the time wasn't ready to fix it, so i resold it.
I simply adore 12xx series. I think is pity that series is not in production anymore.
Now... on this schematic; i am not sure if it is accurate. I use existing one as starting point.
And intend to change lot on it. Would it be success? I can't tell.
I find great pleasure in journey, more than reaching final destination, that's all.

[Nandor]

I like this topic, it gives me that good old TGSL topic vibes with great talks and interesting ideas. I hope it will be interesting to others to as it's for you and me!

[Nandor]

Nice rework on the Front end
Original is really sophisticated, the guy who made it had a really good day that day!
I did not really understand the Fisher type power supply, why 6 volts and 2.5volts can you explain it please?

regards

[ivconic]

Nice rework on the Front end
Original is really sophisticated, the guy who made it had a really good day that day!
I did not really understand the Fisher type power supply, why 6 volts and 2.5volts can you explain it please?
regards

I can't explain it to myself either.
Similar to 12xx series.
We elaborated 1265 model here on forum, quite while ago.
I forgot all the important conclusions we had than. should use search option to remind myself.
But from a first glance is obvious that SiVP0104 fet is having complex role there.
Kind a "soft start", protection and regulator.
I added on schematic possible substitution without that fet, since is impossible to obtain it in local shops.
Also i recall that i successfully replaced it on one broken 1265, with ordinary fet. Can't recall which one.
OP37 i put more like "principally" solution, in reality i don't plan it but another more modern opamp with better specs.
From what i already checked on the bench is TX part, 4060 based oscillator and 4013 based phase shifter.
I can confirm that stage is working alright. Much better solution than damn transformer.
I took 9.5Mhz crystal value as just probing example. I wonder how would it perform with higher frequency.
Later on when complete device finished; will be easy to check this, by simple crystal replacement
10Mhz, 10.450Mhz, 10.7Mhz. All close. Giving slightly higher working frequencies.
So, by now; TX part with phase shifter is tested on bench and proven.
Problem is; i work parallel on 2 other projects, quite different than this one.
So it will add some delay in my work on this.