In my system, in the radio...

[hung]

Have you tried using something other than a 555? The reason I ask is that the TTL 555 uses a lot of current and typically causes spikes in the power supply. This noise could be what affects your FM receiver even though it may be on a separate supply. Just trying to narrow down to the real scenario here. A CMOS 555 is available and pin compatible. Interested to know if you have tried both.

Is your FM receiver set to a station or just noise? What is the change in sound?

bklein, a CMOS555 is too fragile for this (LRL case). It is prone to burning by thunderlights, bolts and electric spikes. A regular 555 is more robust.

Regards.

[WM6]

A regular 555 is more robust.

.

555 have to be robust as 666 one, because we are compelled to beat by pistol the first in pocket found coin, to push them tell us where the remaining coins are buried.

[bklein]

bklein, a CMOS555 is too fragile for this (LRL case). It is prone to burning by thunderlights, bolts and electric spikes. A regular 555 is more robust.

Regards.

I really would like to know if the type of 555 is a factor here.
If a ttl 555 dies from what you suggest, so would my cellphone and anything else around. I can put a tvs diode across the supply to totally prevent ESD from killing it. But anyway it is cheap. Besides those things would make the day a lousy detecting day anyway because they would obliterate the fields intended to detect....

Did you really evaluate one vs the other?

[J_Player]

I really would like to know if the type of 555 is a factor here.
If a ttl 555 dies from what you suggest, so would my cellphone and anything else around. I can put a tvs diode across the supply to totally prevent ESD from killing it. But anyway it is cheap. Besides those things would make the day a lousy detecting day anyway because they would obliterate the fields intended to detect....

Did you really evaluate one vs the other?

Hi bklein,
The circuit is a simple square wave oscillator. You could make two of them. One with each type of 555. Then you could see for yourself which works. Personally I don't think it matters. The cmos version has better noise immunity, but I think you will find the same results with each.

Cmos also does not require any special power supply. A plain battery works, and does not matter too much about the exact voltage. If a thunderbolt fries it, then you can unplug the IC and put another in it's socket. They're cheap.

You might also want to stick to the exact circuit Esteban describes. If you add noise-reducing enhancements or a regulated supply, you may find someone tells you you built it wrong. It could turn out that the noise you described is necessary in order to see the circuit response. Your spectrum analyzer will show the small signal variations you are looking for change a lot when you modify the exact circuit that was described.


Best wishes,
J_P

[bklein]

Hi bklein,
The circuit is a simple square wave oscillator. You could make two of them. One with each type of 555. Then you could see for yourself which works. Personally I don't think it matters. The cmos version has better noise immunity, but I think you will find the same results with each.

Cmos also does not require any special power supply. A plain battery works, and does not matter too much about the exact voltage. If a thunderbolt fries it, then you can unplug the IC and put another in it's socket. They're cheap.

You might also want to stick to the exact circuit Esteban describes. If you add noise-reducing enhancements or a regulated supply, you may find someone tells you you built it wrong. It could turn out that the noise you described is necessary in order to see the circuit response. Your spectrum analyzer will show the small signal variations you are looking for change a lot when you modify the exact circuit that was described.


Best wishes,
J_P

Exactly. I have played with 555's for 30 some years I would imagine. I don't want to go to all the trouble and then have someone say - oh you should have used a xxx 5V regulator not a 78L05, or oh not that LED this one, etc.

[Fred]

Exactly. I have played with 555's for 30 some years I would imagine. I don't want to go to all the trouble and then have someone say - oh you should have used a xxx 5V regulator not a 78L05, or oh not that LED this one, etc.

Exactly.
I suppose this is why you never find a complete (real) schematic around here.

[alnamr]

hi

look thes

[Morgan]

BFO

look thes

This is primitive BFO,works with one radio,i build this many years ago,it works great,detects one coin underground,not more than 5 cm

[detectoman]

hi, i too build these, but your should put an radio very adecuate to oscilation tx coil, not all can work here, is major an radio very early, what has audio transformer and transformer for conversion, any radio sound here pretty, other no, then need put the tune in an point of dial with sound white, then emit radio reponse, these put detect discriminate, only put an adecuate transistor radio and frecuence due
right tx, right radio, right calibration, wtb,true morgan, this is short depth, may be can convert in lrl, whit complex, esteban implementation
very good sound, strong potente, and clear can emit these stuff
no movement, no ground affected, little comsume, but is all metal

[detectoman]

is major for these project, any radio what other, put preference mini radio old,of pioners, due modern radio base ics, may be not work ok in conjunction, or only emitt distant sound, no good new radios, may be exist any exception