CZ6a iron tone mod...

[tincanalley]

The CZ6a (as most detectors) will give an iron tone for targets that are too deep for it to reliably identify. Many times when beach hunting, I will dig those weak sounding iron tone signals knowing that they could possibly be something good. My problem is that all the iron surface trash, which comes in at maximum volumn levels, is very fatiqing to my ears. I would like to limit the maxium volumn level of this iron surface trash without losing the weaker "non-identifyable" iron signals. I would think that adding a small limiting circuit somewhere on the PC board would acomplish this, but need info on what type of circuit and where to insert it. Reducing the "iron tone" level to about 50% would be ideal. I don't think I need the circuit to have an adjustable volumn level but it may be easier to find the correct amount of reduction I was looking for.

Any help in this project would be greatly appreciated.

Thanks!

[Davor]

I did not have a pleasure to see the schematic of this rig, but from what you are asking I conclude that you are happy with one shortcoming so much that you wish to make further accommodations for it. I'd seek a solution to false iron first

[Qiaozhi]

The CZ6a (as most detectors) will give an iron tone for targets that are too deep for it to reliably identify. Many times when beach hunting, I will dig those weak sounding iron tone signals knowing that they could possibly be something good. My problem is that all the iron surface trash, which comes in at maximum volumn levels, is very fatiqing to my ears. I would like to limit the maxium volumn level of this iron surface trash without losing the weaker "non-identifyable" iron signals. I would think that adding a small limiting circuit somewhere on the PC board would acomplish this, but need info on what type of circuit and where to insert it. Reducing the "iron tone" level to about 50% would be ideal. I don't think I need the circuit to have an adjustable volumn level but it may be easier to find the correct amount of reduction I was looking for.

Any help in this project would be greatly appreciated.

Thanks!

I would suggest using a speech processor circuit. These were a popular add-on for CB Radios, and there is a 4-transistor circuit in the book "C B Projects" by R. A. Penfold (Bernard Babini Publishing Ltd). The book was published in 1981, and there is actually a copy available on the UK Amazon site here ->
http://www.amazon.co.uk/CB-Projects-...406781&sr=8-51

You could also try searching the web. I found a simple 1-transistor design here that might be worth trying ->
http://www.tradeofic.com/Circuit/135...PROCESSOR.html

The idea of the speech processor is to boost the low amplitude signals while compressing the high amplitude ones. For a CB radio it allows weaker signals to be heard without blowing your ears off when a loud signal is received.

[tincanalley]

The CZ6a already has a low amplitude gain once you dial the volume control above "5". It will then boost the weaker signals without boosting the already loud signals. What I looking for is a way to reduce "ONLY" the loud "iron tone" signals (which is 200 htz). I've tried adding an electroletic capacitor (1uf) to the output of the detector before it goes to the headphones but have had no luck so far. This may require a dedicated notch filter for 200 htz.

The CZ6a/CZ5 (CZ5 being same as CZ6a but w/o water resistant housing) circuits are the same, so if anyone has a CZ5 schematic and can figure out where and/or how to do this in the circuitry, please advise. If it will have to be done at the output jack, please advise on that also.

Love the detector, but being that there are 100's more rusty iron nails in areas I hunt than good targets, reducing the volume of these iron tones would be a blessing!

[Old cart]

A passive notch in the headphone jack is the way to go. You can use this calculator to determine the correct values.

http://www.mh-audio.nl/parallelnotchfilter.asp

For impedance you can use the dc value that you measure with an ohmmeter on your headphones. The r value adjusts the attenuation of the low tone.
Let us know how this works.

[Paul99]

Is anyone having difficulty accessing...

http://www.geotech1.com

I get "Hacked by Don" when I click the above link..