Surf PI - successful build

[SVEN1]

I never knew your name was George I thought you might be japanese because of your logo.
Chris

Funny you should say that, years ago that's what I thought

[DOOLEY]

Funnily enough,
There's a crossbow for sale on eBay UK.

The seller says only 17 of them built......
Different number there to what George states.

So going by recent reading,
May not be a genuine "George" unit ........
As it sounds like more were made.

Other thing said was it discriminates iron,
Is that an advertising ploy or true ???

[SVEN1]

Funnily enough,
There's a crossbow for sale on eBay UK.

The seller says only 17 of them built......
Different number there to what George states.

So going by recent reading,
May not be a genuine "George" unit ........
As it sounds like more were made.

Other thing said was it discriminates iron,
Is that an advertising ploy or true ???

Actually the listing says 13 built.
It's one of George's.
There's enough basic info on the web about the CB, as George mentioned it's a modified Hammerhead.
https://www.google.ca/search?q=cross...ADA&gws_rd=ssl

View the Hammerhead article and you will see how you can experiment and customize the tuning to your needs. Basically that is what George did for his customer for the purpose the CB was built for.
http://www.geotech1.com/cgi-bin/page...head/index.dat

[SVEN1]

hello chris,

two years ago or so the crossbow were made in a ldt count of ten or twelve units
that what i have heared from uk dtectorists who had the luck to get one was good
they loved the peformance on uk coastline and inland

had missed my chance to buy one but was some pounds over my possibilities in this time

but later i decided to truy a rebuild but didn´t finished

HI,
I have one PCB for the Crossbow left that I can spare, if you want take another try at completing one, let me know, will send it out to you.

[Qiaozhi]

Hi George, thanks for the info. Its good to know I can use other coils with the crossbow. The pictures look great, I dont know if my homebuild will look quite so good.
By the way, we have had contact in the past, and I never knew your name was George I thought you might be japanese because of your logo.
Chris

Funny you should say that, years ago that's what I thought

My avatar is actually Chinese (not Japanese).
Qiaozhi is a common transliteration of George. In other words, that's how George sounds to Chinese ears. Zhen de me!

[Qiaozhi]

Funnily enough,
There's a crossbow for sale on eBay UK.

It was on there recently, but the auction has finished.
I think one or two people have tried to cash in, due to positive user feedback and the extreme rarity of these machines.

The seller says only 17 of them built......
Different number there to what George states.

So going by recent reading,
May not be a genuine "George" unit ........
As it sounds like more were made.

There were definitely only 13 made, and unit #1 is here next to me.

Other thing said was it discriminates iron,
Is that an advertising ploy or true ???

It's a classic PI, and as such cannot discriminate iron. Some users say they hear different sounds for iron, but personally I wouldn't trust that as a guide.

[chrisw]

Thats interesting I often wondered what it meant, I just asked my wife what your avatar said, she confirmed it said George.

克里斯 (Chris)

[Qiaozhi]

Thats interesting I often wondered what it meant, I just asked my wife what your avatar said, she confirmed it said George.

克里斯 (Chris)

I guess she's either Chinese and/or understands Mandarin?

[chrisw]

Yeah she's chinese, came from China to Uk 8 years ago.

[multieagle]

Building the Crossbow will not be an easy task, and I certainly wouldn't recommend anyone to even try it if their electronics knowledge is weak, or they don't have an oscilloscope and understand how to use it.

Thank you. Being a novice, this may be beyond my skills. However, will attempt one of two boards . . . VERY SLOWLY following in other footsteps.

[6666]

Hi Bernte_one,
My Mirage seems ok but I cant quite make the 30 cm mark yet, but I am still experimenting with coils. Also it is very sensitive an needs regular frequency adjustment. So I will have a go at the crossbow.

Chris

Chris can you please explain why you need constant frequency adjustments ? what does your machine do to require it ?

[SVEN1]

Chris can you please explain why you need constant frequency adjustments ? what does your machine do to require it ?

He has problems with EMI in the home so he can't find a stable frequency to keep the threshold a contant tick. He is using one of the new version boards where we
changed from a trimpot and with an external frequency control to a fixed PCB resistor and with an external control. The external frequency control only needs to be adjusted a very tiny amount at a time.
can be an issue for some. I am going to try a multi-turn control pot for the external freq. control.

[6666]

He has problems with EMI in the home so he can't find a stable frequency to keep the threshold a contant tick. He is using one of the new version boards where we
changed from a trimpot and with an external frequency control to a fixed PCB resistor and with an external control. The external frequency control only needs to be adjusted a very tiny amount at a time.
can be an issue for some. I am going to try a multi-turn control pot for the external freq. control.

Hi, ok so its a EMI problem, is the pcb inside a metal box ?

[SVEN1]

I may have mixed up Chris W in the UK with Chris W in Oz.

[chrisw]

Hi 6666,
Yes Sven has got it right. Its not as bad now as it was when I first built it, but still occasionally the emi causes a need to adjust the frequency to make it quieter. But once the detector is settled it works very well. Then a little later its as if it wakes up and starts to make noise again, so another adjustment is required. Since most of my life I have used VLF machines, I am not used to having to make any adjustments. But to be fair I haven't tried my detector away from home, such as on the beach. In my area I think there must be a lot of emi noise.