Surf PI: Cable between coil and PCB

[Nicolai]

Guys, I need some help here.
I built the PI kit from silverdog and wrapped some speaker cable for my coil.
Just testing on my floor, swiping tools above it, it seems to work fine.
I have just used the same speaker cable, to connect to the PCB.

How ever, everywhere I read that I should use coax cable to connect the coil to the PCB.
When I do that, I end up with a terrible result, where it doesn't detect ANYTHING.

So, am I doing something wrong here? Should I just stick with using the speaker cable?

I am not expert on any of this, but I assume I should use the inner lead and the braided wire for my connections?
My latest attempt, is using RG-58 cable. There's a foil between the braid and the insulation for the inner lead, should I remove that?

[kt315]

....................

Re: Eric Foster PI Search Coil Wire
Posted by: Eric Foster [ Send a Message ]
Date: November 25, 2012 02:15AM
Moderator
Registered: 10 years ago
Posts: 311
Hi Sven,
The orange cable is a specially made RG58 coax. It is made for the offshore industry, specially for underwater use, with a polyurethane outer jacket rather than pvc. This is much stronger and hard to penetrate by contact with sharp edges. Water at pressure would very quickly siphon along ordinary coax if there was even a small cut, and enter the coil windings. Salt water would write off both the coil and the cable and even enter the electronics unless a water blocking connector was used. Of course the orange coax is considerably more expensive, but I thought it was worth it as even for shallow water work it gives added protection.
Eric.

[Nicolai]

....................

Thank you for your reply but I'm not really sure how that answers my question.

[kt315]

did you search forum before asking?
http://www.geotech1.com/forums/searc...hid=382595&pp=

[Xtrem]

Guys, I need some help here.
I built the PI kit from silverdog and wrapped some speaker cable for my coil.
Just testing on my floor, swiping tools above it, it seems to work fine.
I have just used the same speaker cable, to connect to the PCB.

How ever, everywhere I read that I should use coax cable to connect the coil to the PCB.
When I do that, I end up with a terrible result, where it doesn't detect ANYTHING.

So, am I doing something wrong here? Should I just stick with using the speaker cable?

I am not expert on any of this, but I assume I should use the inner lead and the braided wire for my connections?
My latest attempt, is using RG-58 cable. There's a foil between the braid and the insulation for the inner lead, should I remove that?

Normal RG58 , is good, not the best , but ok. I have the same problem in the past, using RG58, but it was made from Iron,
Check the Cables you are using with a strong neodumium magnet , most cheap chinese are made from iron.
You must be shure , you are using cable made from COPPER.
Aluminium cable is Inappropriate too , you can identify it that you cant solder it.

[kt315]

there are different RG58's. you have to choice multistrand.

[homefire]

You can use some better quality Audio cable like for stereo .. Keep the RCA jack and use that too. The Surf is not all that picky.

[Nicolai]

Normal RG58 , is good, not the best , but ok. I have the same problem in the past, using RG58, but it was made from Iron,
Check the Cables you are using with a strong neodumium magnet , most cheap chinese are made from iron.
You must be shure , you are using cable made from COPPER.
Aluminium cable is Inappropriate too , you can identify it that you cant solder it.

Yea, I'm pretty sure it's aluminium. Awesome, haha.

[Nicolai]

You can use some better quality Audio cable like for stereo .. Keep the RCA jack and use that too. The Surf is not all that picky.

[ATTACH]39548[/ATTACH]

So basically, I can just use whatever gives me the best results, that I have on hand, and not worry about interference or anything, right?

[homefire]

No not anything. Audio cable is Shielded and Stranded core wire. Just happens to be suitable.

[Tibuck19]

No not anything. Audio cable is Shielded and Stranded core wire. Just happens to be suitable.

I use Gs-6 coax that's made in Japan which is basically a good guitar coax, Seems to work well enough for the PI on here that I've made. now is it Good for long term salt water use??? no clue

[Ferric Toes]

As has been mentioned, RG58 can vary a lot. The one I use, RG58A/U, has tinned copper braid and core. The tin plating introduces enough resistance between the strands so that the part of the cable near to the coil does not give false signals due to eddy currents in the braid. A lot depends on how short the sampling delay is. At 10uS things are more critical than at 15 or 20uS.

I have not seen RG58 with aluminium foil shielding or plated steel for the inner core. Using either will give big problems. Do not use RG59.

I once tried some nice flexible microphone coaxial cable which appeared good until you moved it, when it acted like a microphone. I found that this was due to a semiconducting layer under the braid, which is supposed to stop cable noise.

Eric.

[Tibuck19]

As has been mentioned, RG58 can vary a lot. The one I use, RG58A/U, has tinned copper braid and core. The tin plating introduces enough resistance between the strands so that the part of the cable near to the coil does not give false signals due to eddy currents in the braid. A lot depends on how short the sampling delay is. At 10uS things are more critical than at 15 or 20uS.

I have not seen RG58 with aluminium foil shielding or plated steel for the inner core. Using either will give big problems. Do not use RG59.

I once tried some nice flexible microphone coaxial cable which appeared good until you moved it, when it acted like a microphone. I found that this was due to a semiconducting layer under the braid, which is supposed to stop cable noise.

Eric.

Isn't RG58A/U a VHF CB antenna cable? I don't think you could get it in double shielded core like something along the lines of a XTL cable? 2 shielded wires with an outer braided shielding? In that case, what would you use if one wants to make a DD or other coil that has separate TX and RX ?

[ionut_mtb]

i have some rg58 with alu foil shield.