Minipulse build

[petere]

I can see the battery pack is connected by flying wires. I assume you didn't accidentally connect the battery pack in reverse?

That is a possibility. I cannot say for sure either way.

[petere]

What is the correct way to set up volume control on the MPP?
I have replaced R28 with a 5K audio pot, it works but I cannot get the volume low enough.
I will only be using headphones.
Cheers

[Xtrem]

Connect parallel to R27 a 100K potentiometer as a Volume Control.

[petere]

Thank you for the suggestion Xtrem but it did not work.
there was no variation in volume until the knob was turned all the way around and then the sound turned off

[petere]

Think I got it sorted. Sketch attached.
I found that a 100k pot worked better than the 5k. Might try a 250k when I can get hold of one.
If you have your electronics in a metal box make sure the earphone socket is isolated from the box.
Cheers
Hope the sketch makes sense

[Xtrem]

It is not the correct way to set the volume at the output of the 2N3906,
let the circuit unmodified at the output....,R28 protect the 2N3906.
the easy way is to connect parallel to R27 a poti,
or replace the R27 with a potentiometer.
it work perfect.

[petere]

Finally got everything packaged up.

Made an enclosure with separate battery compartment from aluminium sheet.
The power supply at this stage is 4 Li-Ion batteries with a voltage regulator set at 12v but this may have to go because I think it has introduced noise into the circuit.
Most of the mods are from KRinAZ, Thank you.
TX pulse width is 30us
Frequency set at 4000. May put an external pot for this at a later stage.
Main sample delay min is set at 6us
Sample pulse width is set at 22us
Sample delay is 130 us.
Very happy with the outcome.
Plan on testing it in the goldfields on the coming weekend.
I have read through most of the posts and would like to thank all the contributors.

[geoscash1]

Nice work, congrats on the build.

May I ask where you got that coil and are they available somwhere, I am tired of trying to build a good coil and would like to source a coil I can use with builds like this.

[petere]

Hi geoscash1
The coil is an Australian made Nugget Finder brand. The one I have is a 14x9 Advantage model, mono elliptical wound with litz wire.
They have a new model out now called the Evolution which is getting quite good reviews. I believe it is spiral wound.
I think they export to your part of the world.
Cheers

[6666]

Hi geoscash1
The coil is an Australian made Nugget Finder brand. The one I have is a 14x9 Advantage model, mono elliptical wound with litz wire.
They have a new model out now called the Evolution which is getting quite good reviews. I believe it is spiral wound.
I think they export to your part of the world.
Cheers

About 390 Aussie dollars, so back to home made

[geoscash1]

Whoaaaaa pony, holy crap, those must be made of gold.......

6666, your right, back to homemade for sure.....lol

[Tim]

About 390 Aussie dollars, so back to home made

Bloody extortion, I say! Like everything lamebin related. I begrudgingly paid $100 for my 10x5 commander DD. The first thing I did was cut it open. An enamel winding, a litz winding and a couple of sheets of graphited paper. $30-50 of materials, pay the pimply-faced apprentice $8/hr, to assemble it, and give the rest to the shiny bums in the office.
Some scammers are asking $14 for a single lamebin plug when you can get 10 plugs and 10 sockets for less.
The old saying about too many dollars and not enough cents/sense comes to mind here......