straight cable.

[Anonymous]

hello frank and friends forum,
Some time ago i discover this small problem of the round spiral around the shaft like a coaxial balun (i agree Frank ), changing the pattern of detection in some ways.
To resolve this , in my own pulse detector the lower pole is empty with two oval holes, and i can put the connector with cable INSIDE the tube shaft going straight ,and go outside before the upper pole...
It is a good design and it work great in the field because you can not bump o hook anything with the cable ; the lower tube is more large in diameter than normal and go straight with the upper pole (mils.design). i will post a photo in another message,because it is difficult to explain with clarity in my poor english, but i hope you will understand.The fact exist i also notice the phenomenon...explanation in a near futur ???

 

[Anonymous]

I was looking at an advertisement for the GP, and noticed the cable is straight on the lower shaft. Was this done for a reason?

 

[Anonymous]

Dear Sirs:
A lot of work was done early on - between the 2000 and 2100 SDs to quieten down the cable noise of all SD coils, - monoloop and 'dd', this was acheived by using PUR1 wires in the coax for the spiral lap shields. This makes for a cable which is 'invisible' to the coil even when flexed, - This is not patented, - probably should have been, - too late now. Eric is aware of this, - I sent him some a couple of years ago, - the cost of the cable is pretty high as it has to be specially made for us.
Cheers John Kah Coiltek

 

[Anonymous]

Hello John Kah,
I prospect with a SD2100 12v & 14" coiltek mono, the coiltek coil made a big difference over the stock 11" DD. I just bought an Infinium LS last week, and was pretty disappointed in the performance of the 10" X 14" DD elliptical coil, it got descent deepth and ran extremely quiet with a very steady threshold but compared to the SD it lacked depth. Could I expect the same increase in performance with a 14" round mono on the infinium?
If Coiltek or Eric would build a 14" round mono, I would be the first to buy it. Are there any plans or possibilities of making a coil for the Infinium? Happy hunting! Thanks, Russ

 

[Anonymous]

Hi John and all,
Yes, that is the way to go - using individually insulated strands on the braid. I tested a length of your cable on my hi speed PI and the decay time was about 1uS, which would be totally invisible on standard PI's. By comparison, RG58 has a decay of 8uS when straight and double this when stressed in a curve. In my last post I mentioned the variation between manufacturers, well my underwater RG58 measures only 5uS when straight and 10 when flexed as it has a looser braid.
So, there seem to be sound reasons for keeping the cable straight on the Aquastar and Goldquest and the operating instructions will be amended accordingly.
Eric.

 

[Anonymous]

Eric... I'll bet that's why some people reported falsing when in the surf. The wave action was causing cable movement?

 

[Anonymous]

Hi Jeff,
Possibly in some cases. It is only the 10in or so of cable nearest the coil that can cause the problem. As the cable goes up the shaft and away from the coil edge, any signal from the cable would rapidly become too weak to have any effect.
What seems to worsen the problem is that the braid wires have to be soldered together to connect them to the ground end of the coil. The fact that they are soldered rather than just touching, increases the eddy currents at that point. I have noticed that even the SD cable can generate false signals when flexed near to the coil entry, due to the otherwise insulated braid wires having to be soldered. However the effect is small compared to standard coax.
I have always recommended that the cable at the coil end be taken straight to the shaft, without any loop or slack, and Velcro'd to the lower shaft end to prevent any movement.
As PI sensitivities rise, this is a problem that needs to be addressed and I have a few alternative "off the shelf" cables that look good in that they generate no detectable signal. Other considerations need to be looked at though, such as durability and resistance to cuts and abrasion.
Eric.