Bara sensitive to motion. How to solve that problem?

[bernte_one]

baracuda works ok so
you will get only a signal at end of every sweep, but there is a clear difference between a target signal and this light swinging signal
i am not sure if it is really earth magnetic field what you hear, and this will not disappear with your heavy shield of alu tape
better use graphit powder

[Psyborg]

I try with graphit powder also. The same problem.
Maybe i will make a video.

[sinclairuser]

i built two barracudas, one as per kit, and another with ceramic chips, metal can transistors, .1 resistors, wima caps and millitary spec components where available.
i wanted to see if tighter tolerances made much difference, at first it was rubbish, it would beep at the end of the swing, tests proved it was the coax flexing that caused it.
after changing the coil wire to microphone coax it went away, after that it was excellent very stable, and yes higher spec components do increase stability, but not enough to warrant the extra cost.
after some chip swapping tests i found that ceramic texas instruments 40106 ic's, and metal can tip127(old very rare), made the most difference, after i changed these components in my other barracuda kit to these versions, it was just as stable.

i would look at the coil and cable worth a try.

[Psyborg]

Perhaps the Earth Field elimination is not working. That would account for it being ok on the bench (non-moving coil), but beeping when the coil is moved. Does it beep on the bench when a magnet is waved in front of the coil? Of so, then check the EFE part of the circuit.

What parts are EFE part of the circuit?

I will try with microphone cable.

[Qiaozhi]

What parts are EFE part of the circuit?

Have a look at the attached schematic. I have marked the main and secondary (EFE) sample gates.

[6666]

Nothing has attached

[Qiaozhi]

Nothing has attached

Don't you just hate it when that happens?

[Psyborg]

On my barracuda these two transistors Q3 and Q4 are different. Q3 is 2n5485 and Q4 is MPF 102. Should not they be the same? Baracuda is version Alex/Ap rev2

[Koala]

In your kit did you not get 3 FETS two the same and one different. You could swap two over so Q3 and Q4 are the same. There was a discussion on the main Baracuda thread about a performance advantage of matching Q3 and Q4

Board is marked with different components for Q3 and Q4 ????

[silverdog]

The pcb Alex / ApRev2 is based on this reversed schematic from the original Baracuda - which has different Q3,4
That is not to say of course that findings since prove Q3,4 are better matched

[Psyborg]

In your kit did you not get 3 FETS two the same and one different. You could swap two over so Q3 and Q4 are the same. There was a discussion on the main Baracuda thread about a performance advantage of matching Q3 and Q4

Board is marked with different components for Q3 and Q4 ????

Yes, on board is marked different. I will try to swap. I hope this will help.

[Impulse]

Did you ever solve this problem?

[kt315]

In your kit did you not get 3 FETS two the same and one different. You could swap two over so Q3 and Q4 are the same. There was a discussion on the main Baracuda thread about a performance advantage of matching Q3 and Q4

Board is marked with different components for Q3 and Q4 ????

those are same FETs. identical. NOT DIFFERENT. do not take attention on that. I setted BF245's and they working in all places (inverted position of course).

[Impulse]

Im not going to start moving components around, its just when i connect my coil i get the same issue any small movement and i get a response and the coil is about 1M of the floor

[Impulse]

ok i have sorted the coil movement issue it was the coil cable movement causing the response issue yay something simple to fix!