VLF vs PI SHOOTOUT PROJECT

[Carl-NC]

Coils do have flat voltage response...

Ideal coils have a flat voltage response. Add in distributed parasitics, and they don't any more.

[Davor]

... but deviation from ideal in terms of -3dB range spans well over a decade.

[Carl-NC]

Yeah, I'd agree that with some effort you can get a good decade of decent flatness. I built a wideband coil intended for 2k-50k, and it worked really well up to 30-35k, beyond that was difficult.

[Altra]

I built a wideband coil intended for 2k-50k, and it worked really well up to 30-35k, beyond that was difficult.

That is what I have experinced. At about 30khz things change and become more critical.

But, I can still play with a fundimental, 3rd and 5th without much trouble under 30khz.

[moodz]

Hi Moodz,

I am well aware of the sweep function. The challenge is to have TX and Rx stages with a flat response across sweep range.

Regards

I thought you would be ....

I work in digital video nowadays but in the "old analogue" days we used to make up equalisation circuits for this type of application that were certainly flat to around 3.5 Mhz and good to around 5.5 Mhz ....this type of equalisation was used to send color video over 2 - 3 Kms of twisted pair phone line ( ie your regular phone line ). To keep the color accuracy and detail the phasing and amplitude distortion had to be reasonably low .... so equalising a coil for say a max top frequency of 500 Khz should be a piece of cake.

[Altra]

Sounds good Moodz, you can give me some pointers on equalization when I get the software worked out. The chip also has pga's on the
Tx and Rx which could be used to compensate for roll off. Although they don't have much resolution. I think the data could also be weighted?

[medj]

Thank you for your responseBut there is no answer to my questionI'm tired valuable making the circuit and I do not want to fatigue in making Rex TexI will put you pictures of the deviceI want the owners of the experience that show me the rolls of wire with a diameterCan I change my cut or notAnd that the device is good or notAnd machine-made by giving me information about itYou sincerely
http://up13.up-images.com/up/viewimages/888f4a74b1.bmp
http://up13.up-images.com/up/viewimages/ecd40072dd.bmp
http://up13.up-images.com/up/viewimages/d6a856b69d.bmp
http://www.4shared.com/rar/XY5vQRbi/delta_01.html

[mikebg]

....My application idea for this chip is similar to the Geophex GEM-2.
It scans a number of frequencies and then plots a composit based
on resistivity and phase. More info here
http://www.geophex.com/Publications/...uly-August.pdf

Altra,
If you use information from this paper, please don't use their loop configuration. The authors don't know that search head shoul have induction balanced loops and should be moved close to ground.

I expect you to show how they look the frequency characteristics of different objects: coins, rings, bracelets, nuggets and hot rocks.

[Altra]

Altra,
If you use information from this paper, please don't use their loop configuration. The authors don't know that search head shoul have induction balanced loops and should be moved close to ground.

Your statement is wrong. At this point I think you are pushing buttons to get attention!

These guys know exactly what they are doing. Balanced and unbalanced designs.

http://www.geophex.com/publications.html

http://technology.ssc.nasa.gov/suc_s...d_sensors.html

Patents
US5963035
US5557206
US6204667

[medj]

First, thank you for sitesSecondly, I want attention for the projectFor the benefit of everyone hereWhen he finished the project lift it here on the site I'm not selfish like someToday I Make a device that the device does not work well Tell that he was not goodYou make the other and tell that good or notBut we must not lose total
We are here to exchange expertise and experiences
Thank you for your interest in my brother
..........................
It is importantI want to inquire There is no reference in the projectBut if you put one hand fingers on the base of the transistorAs in the pictureThe device captures a signal metalReference 1 meter and once 20 cm