A VLF RECEIVER

[Alex]

Anybody has the time and patience to make a PCB from this
vlf receiver schematics? .I have a small idea to use it with other device
as a LRL .R4 is 22M and I cannot find so big value so I have to use 5 resistors in place...
Any help welcome.
thanks

Alex

[Alex]

here the schematic:

[Fred]

Hi,

this receiver has no tuning circuit, i´t s just a filtered amplfeir ?
So i guess you must connect it to a computer to "see" signals...
regards,
Fred.

[Alex]

Hi Fred

Yes this is only filtering and amplify the signal up to 20 kHz .Is good for gold
and silver frequency.Of course you need a laptop to see the signal..also you can listen on the phone...Need other device too.
I have to make first this one after I will try and do experience outside..

[Fred]

Yes this is only filtering and amplify the signal up to 20 kHz .Is good for gold
and silver frequency.Of course you need a laptop to see the signal..also you can listen on the phone...Need other device too.
I have to make first this one after I will try and do experience outside..

Hi alex,

From 0 to 20khz you are going to pick up plenty of signals, natural and not-so-natural , but i don´t see how you can detect any metal with it , and less discriminate between them.
anyway it could be an interesting experimentto to go around with a laptop and see what happens.If you detect a multi-thousand tons moving and radioactive metallic item, don´t be afraid it´s just a submarine.
Good luck,
Regards,
Fred.

[Alex]

Hi Fred

Is ok.I ask something and until now you didn't answer me. I need the PCB. .I know I can hear a submarin even a angel .A good one .
You are a guru not me, so if you want you can add a fine tuning at this schematic for 5Khz and 8.7khz.
This can be your help in this project.Wait until the end....
I told you there is another device in this but we will talk later .First step build this ,make the improvment ..and see.

[Fred]

Is ok.I ask something and until now you didn't answer me. I need the PCB. .I know I can hear a submarin even a angel .A good one .
You are a guru not me, so if you want you can add a fine tuning at this schematic for 5Khz and 8.7khz.
This can be your help in this project.Wait until the end....
I told you there is another device in this but we will talk later .First step build this ,make the improvment ..and see.

Hi Alex,
To be a guru you only need to talk a lot, this doesn´t mean you´re good at it
Anyway i will try to make the PCB, i will post it a soon as i can.Switches and leds will be out of PCB.For R4 (2X 4M7) + (2X 6M should be OK.
I assume L1 and L2 are 1/2W size or so.I don´t know exact pinout of F1(fet), but that should not be a problem.
regards,
Fred.

[Alex]

Hi Fred

Thanks for your help.I need to add something before to start do the pcb.You have to know this:
The FET Gate resistor R4 is the main component that determines how much of the voltage
captured by the antenna will actually be amplified in the receiver. Stated a different way, R4 determines the ultimate sensitivity of the receiver. The value chosen for R4 (22MΩ) is a compromise value considering costs, component availability, circuit board layout and receiver sensitivity. For maximum sensitivity a value >100 MΩ should have been chosen.
If you think you can make R4 BIGGER do it for more sensitivity...
thanks a lot
Good work.
Alex

[Fred]

Hi Alex,

You can find here the PCB.
IT shoudl be re-verified, please let me know if there is mistakes or improvements.
Hope the shape of PCB is OK for you
Highter definition files zipped .
Happy building,
Regards,
Fred.

[Alex]

great WORK

Really thanks Fred.
Yes the shape is perfect what we need.I will control the pcb tonight.
I want just to thanks you again you did in so short time.
Greatings
Alex

[Alex]

Hi Fred

Do you think is it possible to have a series of led at the output of
signal so you can have a idea when it became stronger ...or you are closer to
target?.
THANKS

[Fred]

Hi,
Here is a PCB for a sensitive vu-meter that use led row.
I have built it, i works fine.
Hope it helps!
regards,
Fred.

[Alex]

thanks Fred

I really appreciate what you done ,so fast and nice work.Yes the leds are good.I will try to make it this days.
I don't know in your country but here is a Passover tomorow ,so I send you my best wishes anyway.
Have a nice weekend.
Thanks again
Alex

[Fred]

Hi Alex,

Yes ,here too, so we have 3 days in a row
Good luck with your project , and best wishes.
Regards,
Fred.

[Dell Winders]

For what it is worth, it is pleasing to see you cooperating and working together in friendship. With my best wishes. Dell