Surf PI - successful build

[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.

[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!

[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.

[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=crossbow+classic+PI&ie=utf-8&oe=utf-8&client=ubuntu&channel=fs&gfe_rd=cr&ei=7F_bVNaCCaXz8wfIpIHADA&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/pages/common/index.pl?page=metdet&file=projects/hammerhead/index.dat

[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]

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

[SVEN1]

Hi George,
There was three of us who made an attempt at building the CB a few years ago when I had 5 boards made up. I got sidelined with my PI and the CB I started finished had a problem, don't recall what it was, it was set aside.
One of us built a working CB and was tinkering with coils. His build was getting Garrett Infinium performance. I was asked if I was going to have some more CB boards made up. Still being curious about having a CB, decided to see how many of us would be interested in trying the project. There were 6 of us. Had some more boards made up for us. This will be a project for us. Going to take the build slowly. Since Michael has the most experience building detectors between us, he'll probably get one finished up first? And help provide an guidence. After a number of years building multiple versions of my PI, based on the Hammerhead, I am in better shape knowledge wise to make another attempt at the CB. I also keep in contact with Rick who has the CB you have mentioned modifing the coils for. He is anxious to see us complete a build...........

[chrisw]

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

[chrisw]

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

[Qiaozhi]

I´m building also the crossbow with PCB from Sven. There are some experiences with DD-coils? What was the main-idea for the split up connection for TX and RX?

The split TX-RX connection is the same concept as with Minipulse Plus. It allows you to use separate TX and RX coils (e.g. induction balance). Then you can have a RX coil with a higher inductance to increase sensitivity. Each coil will need its own damping resistor.

[mschmahl]

I´m building also the crossbow with PCB from Sven. There are some experiences with DD-coils? What was the main-idea for the split up connection for TX and RX?

[Qiaozhi]

George, thanks for this. As the CB deviates significantly from the HH, did you ever establish a build protocol? I'm thinking along the lines of the current Minipulse project, where you establish the funcionality of each section before proceeding with the build. I'm also currently getting organized with Sven's current release.

Gord

There was no build document for the Crossbow, as it was never intended as a DIY kit. After constructing the first unit successfully, I simply populated all the other boards in one hit. Of course, it did help that I understood what I was doing, and had all the necessary test equipment.

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.

[multieagle]

George, thanks for this. As the CB deviates significantly from the HH, did you ever establish a build protocol? I'm thinking along the lines of the current Minipulse project, where you establish the funcionality of each section before proceeding with the build. I'm also currently getting organized with Sven's current release.

Gord

[Qiaozhi]

Hi Guys,
Havent been here for a while. I finished my surf PI and went on to have a go at the Mirage. Finished that one now so I was looking for a new project. I found the crossbow on Svens forum, so I have sent away for a board for that. I believe the designer of that; "George Overton" is on this website. By the way I just read the book "Inside The metal Detector", by George and Carl; excellent book I enjoyed that. The reviews I read about the crossbow say it is quite a deep seeker, anyone on here made one?
Chris

Hi Chris,

The Crossbow Classic PI detectors are based on the Hammerhead design, and were specially manufactured for someone who (unfortunately) never paid. Whereas the Hammerhead is designed as a learning platform, the many options can be confusing and make it difficult for a beginner to construct. Essentially, Crossbow is an HH variant with some modifications. The detectors were eventually sold to cover the manufacturing cost and to make a small profit. There were originally 12 detectors, but one person bugged me to build number 13, and luckily there was one spare enclosure, and enough spare parts left over to make it. In reality they were worth a lot more money, and the performance was excellent. For a couple of owners I made a small modification so that the Crossbow would work with a large Minelab coil (might have been 18"), and Garrett Seahunter coils (both the 14x8 and the 8"), and the supplied 10" mono. The feedback I've had is that the 8" Seahunter coil is the nicest one to use. Someone even converted his to a carbon fibre straight shaft.

Sven contacted me, and I gave him the complete details, and also updated the PCB to REV-B to resolve a couple of small issues in REV-A. The board contains a constant current battery charger circuit on the PCB, which requires an external standard laptop charger.

I've attached a couple of photos of the completed detector, and one of several items found by a satisfied user.

George

[bernte_one]

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
so i went to the mirage pi from sven and found something what was similar in performnce and had also some good features
you will find my machine also in his forum

have this unit still here (one of the older rev. of the pcb)
what i had in mind was that i could get good 30cm in air for a 1€ coin with a 18cm monocoil shielded with copper foil, was imprressing for me this time