Whites Surf PI schematic

[ionut_mtb]

You need to LOOK at the Whole schematic.
U7D is switched at the SAME Rate as the 4093 (switched Once per Pulse/sample cycle).
The LEVEL of the signal through D3 ALSO goes to the base of Q6.

I've edited my post above:

edit: the audio signal that come through D3, from sample1 is cutted by U7D switch, result frequency of audio and voltage variation of sample1 give the amplitude. right?

now, as SCS said, why is like this and no opposite? Does it matter?

[waltr]

Why would be matter when that final signal only goes to head phones?

[homefire]

LOL The Final Stage of Demodulation always ends between the ears.

[scs]

Bulgaria,Sofia,1943-44

[scs]

The problem is a long sound signal and a short pause. This increases the consumption when there is a signal.

[scs]

[scs]

Sound -a better option...

[Tim]

Hello guys
I have a little problem with my SurfPi (Silverdog Kit): the detector in the air work well, but if i bring the coil to the ground, receive sound even if it does not detect metals (false signal).
Do i need to adjust the trimmers better?
Thanks for your help

peppe I ended up using ML commander and coiltek 11DD on my SMproDD. DD arrangement should be easy to modify. Shielded coils. Nearly all our ground in Oz is highly mineralised. The SMpro (tacoma56 ebay) also has external delay- this could be adapted to the Surf temporary or permanent to help resolve the problem. I have also had success using mylarised plastic (powdered milk packet) as a unwired shield on my home-made coils (full sheet across bottom). Also I started a thread here regarding adapting a Vsat arrangement to the surf, receiving some very helpful replies. Though I have not tried this yet.
Sascho (scs) answers are also very helpful. I think this man is a genius. There are a few threads here regarding modifications to the Surf sound if you do an advanced search. From memory the simplest options were a transistor change and/or spkr output from other side of transistor, or a 64ohm speaker. Others may correct me on this.

[scs]

With dd coils you can make very good discrimination ...

[Hoot]

Good morning, just lurking, ordered a surf pi 2 kit - waiting to start assembly.

[homefire]

Welcome: Surf PI 2 ?? Who has those for offer ?

[Sean_Goddard]

Anyone tired using Mylar "emergency" blankets? They're huge and you should be a large number of coils out of one. If it works then maybe making a sandwich with the coil in the middle would give good shielding. The problem is making contact. I have used silver conductive epoxy and glued the drain wires in place AFTER securing the foil I used in the housing.

I just don't understand why so many people are having problems with the SM PI kit from Silverdog.

I bought one, built it EXACTLY as the instructions said, hooked up a 300uH 10" (21 turns of 16AWG wire) coil with shielding (remember the gap or you wnd up with a shorted turn) stuck 12 V into it and it worked perfectly. I can pick up an 18ct wedding band at around 14" in air (after CAREFULLY adjusting delay and threshold).

More than happy with the results. So much that I sold my CS4PI as the kit of the SMPI is much better.

The only thing I can think of are;

1) Poor soldering

2) Putting the WRONG parts in locations.

3) Poor component handling (Anti-Static workbench or mat is a GOOD IDEA)

4) Fake or poor-quality components

5) Overheating components when soldering

6) NOT cleaning the board properly after building. I ALWAYS use isopropyl alcohol and distilled water in a 50/50 mix in an ultrasonic bath with a heater and clean the boards for 2 minutes at 50 degrees C.
BE CAREFUL with this as the boiling point of this mix is 80 degrees C. DO NOT SMOKE OR ALLOW SPARKS ANYWHERE NEAR, hence EVERYTYHING must be grounded or you will be playing a harp. Best done outdoors.

[homefire]

Yep some work better then others. Try this stuff to keep contact ! Works for me. https://www.ebay.com/i/182258631705?chn=ps

[Sean_Goddard]

SWEET Homefire. Many thanks.

[6666]

Anyone tired using Mylar "emergency" blankets?

The problem with them is continuity , if you hold the blanket up to the light you will see along the corners of the folds they wear thin and go open circuit , you need to check a few with a MM to get a good continuity.