Author Topic: Cat5, 6 extension cable  (Read 8320 times)

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Offline Rapp-Instruments

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Cat5, 6 extension cable
« on: July 23, 2013, 01:49:01 PM »
Hi Everbody,

because I'm building ROV's, Towfishes and Sonars and other stuff at home www.rapp-instruments.de I have visited this interesting forum many times.
Some people use Cat5 or Cat6 for extension cables to the transducers up to 100 meters.
In transmitting mode the HF burst voltage at my transmitters reach some 2000 to 3000 V. I wonder if the isolation of the patch cables is good enough to stand voltage stress for long time.
In receiving mode there should be a large attenuation at least for high frequencies like 455, 800 or even 1600 kHz, especially with the normal transducers which represent a high impedance source.
Has anybody measured the image quality difference with Cat cable and without

Thomas


Offline Rickard

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Re: Cat5, 6 extension cable
« Reply #1 on: July 24, 2013, 01:13:10 AM »
Hi Thomas, and welcome!
 
I think 2000 to 3000 V on transmit is more than with the Humminbirds so it's difficult to tell how the ethernet cables will react. There have been no reports on electrical problems when they are used with HBs, though. My ethernet towfish cables use to last for about three seasons, then issues from wear and tear forces renewal.
 
As far as I know nobody has made systematic testings of the effect of cable type on the image. The use of ethernet cables started when the original HB extension cables proved to be poor. 50 m with joined extensions cannot match the results with 50 m ethernet. Some people use other signal cables than ethernet cables and seem to get even better results. But those cables are generally more expensive.
 
Regards,
Rickard

Offline Rapp-Instruments

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Re: Cat5, 6 extension cable
« Reply #2 on: July 24, 2013, 02:55:14 AM »
Hi Rickard,

thanks for the quick reply. So I just try my luck with Cat5e cable.

best regards

Thomas

Offline wreckreationaldivers

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Re: Cat5, 6 extension cable
« Reply #3 on: July 26, 2013, 01:13:11 PM »
On my first twisted pair cable extension cable I tested the electrical connection (plug end only & before transducer connection was made) using an insulation resistance tester @2.5kV (between all cores), no problems were found.

Offline Rapp-Instruments

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Re: Cat5, 6 extension cable
« Reply #4 on: July 27, 2013, 02:11:11 AM »
Hi wreckreationaldivers,

thats  good news because I need a lot of wires. I want to test several transducers at the same time. The XHS 9 HDSI 180 transducer, a homemade 490 kHz long array and a homemade 39kHz highpower transducer for subbottom profiling. And I need another 4 lines for reading deep-, pitch-, roll- and compass data. Until now I use the original HB cable, two coax cables RG174 and one 4 wire telephone line.
From the transmitter/receiver unit the data are send to the laptop where they are displayed and stored.
Another way would be to put the electronics in a watertight enclosure and mount it to the towfish. I would need only low voltage dat connection to the surface.


best regards
Thomas



« Last Edit: July 27, 2013, 02:30:59 AM by Rapp-Instruments »

Offline werethefugowee

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Re: Cat5, 6 extension cable
« Reply #5 on: July 27, 2013, 02:09:42 PM »
A cat-5 or cat-6 question.

Since there are 4 twisted pairs and each pair is twisted at a different rate per inch/CM is there any preference as to which pairs are used, and are unused wires grounded at the source (boat)? Actually the center pin.

Example; blue - right  blue/white - cntr pin

orange - left  orange/white - cntr pin

green - down  green/white - cntr pin

brown - temp  brown/white - cntr pin

or am I on the wrong track here?

« Last Edit: July 27, 2013, 07:42:21 PM by werethefugowee »

Offline Rickard

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Re: Cat5, 6 extension cable
« Reply #6 on: July 28, 2013, 02:02:20 AM »
Quote
Since there are 4 twisted pairs and each pair is twisted at a different rate per inch/CM is there any preference as to which pairs are used, and are unused wires grounded at the source (boat)? Actually the center pin.

I don't know, but I don't think it matters which pairs are used. I have used unused wires in different ways and see no differences in the results. Now I just use them as extra drain wires by connecting them to the shield at the transducer end and the middle pin at the unit end. The wire pairs in your scheme use to be members in twisted pairs. Use one pair for each channel all the way between transducer and head unit for best results.
 
Thomas, your project looks formidable! Have you verified the performance of the long array? I'm curious since I'm working on similar arrays.
 
Rickard

Offline werethefugowee

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Re: Cat5, 6 extension cable
« Reply #7 on: July 28, 2013, 09:44:11 AM »
Thanks Rickard. :)

Offline wreckreationaldivers

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Re: Cat5, 6 extension cable
« Reply #8 on: July 29, 2013, 01:19:41 PM »
Thomas

Like Richard say's have you tried the long array yet?, I too am in the process of building a long array and would like to now if it works well, I'm trying to replicate an array built by tritech (pictured) they wanted over £10k just for the arrays.

For the towfish which i'm currently using I use coax for the down and 2 twisted pair for the sides, the coax for the down works very well, for this next project I was thinking of using 3 x coax (in one cable) anyone got thoughts on this?

Jeff
« Last Edit: July 29, 2013, 09:55:32 PM by wreckreationaldivers »

Offline Rapp-Instruments

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Re: Cat5, 6 extension cable
« Reply #9 on: August 01, 2013, 03:26:12 PM »
Hi Everybody,
I'm sorry to tell that I have not tested either the towfish nor the long array until now.  I have only tested a similar but smaller array with a small radio controlled boat in a very small lake in my home town Munich. Sonar- and GPS data were stored on a SD-card and verified afterwards. I have no boat here in the lakes around Munich, my only boat is a sailing boat laying some 1000km away in Mallorca.
But I have holidays starting following weekend and I am going to a small town in the alps with a nice lake around where I can rent a boat and test the towfish with the long array and the other sensors. There are many test, starting from transmitting power and detecting range, receiver bandwidth and sensitivity , resolution and so on. As soon I have done the test I will present the results in the forum.

Hi wreckreationaldivers

from where do You get a coax cable with more then one line. Perhaps one could use a scard-cable with should have at least 4 lines (video in, video out, sound left sound right)


Thomas



« Last Edit: August 01, 2013, 03:39:25 PM by Rapp-Instruments »

Offline wreckreationaldivers

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Re: Cat5, 6 extension cable
« Reply #10 on: August 01, 2013, 10:19:42 PM »
Thomas

here is an option...

VAN DAMME - 268304 - CABLE, COAX, RGB SYNC, 4C, 75R, 50M

Product Information
•   CABLE, COAX, RGB SYNC, 4C, 75R, 50M
•   Reel Length (Imperial): 164ft
•   Reel Length (Metric): 50m
•   Coaxial Cable Type: RG179
•   Conductor Size AWG: 24AWG
•   Jacket Colour: Red
•   Jacket Material: PVC (Polyvinyl Chloride)
•   No. of Strands x Strand Size: 7 x 0.13mm
•   Conductor Material: Copper
•   External Diameter: 8.85mm
•   Conductor Area CSA: 0.092mm²
•   Impedance: 75ohm
•   Conductor Size AWG: 24AWG
•   Core Diameter: 2.54mm
•   No. of Cores: 4

"Supplier are "Farnell" or "RS components"

Offline Rapp-Instruments

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Re: Cat5, 6 extension cable
« Reply #11 on: August 02, 2013, 01:27:39 PM »
Hi wreckreationaldivers,
i have found the video cable 268304 at Farnell, but it's rather expensive, 11 .30 €/m, or a bit cheaper 251€/50m. There is the other options to use >duplex Cat7 cable< with 8 pairs of twisted pair lines.
On the other hand I have studied today the circuit plans of the L3-Klein 595 sonar sytem. They use a pulse transmitter and a preamp located in the towfish so simple data cables are good enough to transmit the trigger signal and preamplified received signal.

Thomas

Offline wreckreationaldivers

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Re: Cat5, 6 extension cable
« Reply #12 on: August 05, 2013, 11:29:28 PM »
Thomas

In your opinion is coax better that cat twisted pairs?

I'm interested in the idea of transmitter and preamp located in the towfish what plans do you have?

Jeff

Offline Rapp-Instruments

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Re: Cat5, 6 extension cable
« Reply #13 on: August 07, 2013, 02:16:32 AM »
Hi Jeff,
I'm not really shure about that, because people in the forum have good experiences with twisted pair cables.On the other hand normal coax cables have better shielding. But I have found that in Cat7 cables each of the 4 twisted pair lines have individual shields. So the crosstalk schould be quite small.
I have found the plans of an old Klein Towfish. They use a broadband pulse transmitter with capacitor discharge (1΅f, 700V) by a thyristor. The pulse is coupled to the transducer by a stepup transformer.  The received pulse is amplified with a broadband two transistor amplifier and a line driver driving the uplink line. So there is only a small circuit bord in the towfish. The cable need only 4 wires, supply 700V, trigger pulse for the transmitter, received pulse and ground. Only the received pulse line have to be shielded. The 15V supply for the preamp is generated by rectifieing the trigger pulses.
The circuit is similary to the plans of the famous homemade sidescan sonar of Sture Hultquist http://www.abc.se/~pa/sture/
I can link the plans of the Klein-  and Hultquist device when I'm at home again the end of the week

Thomas

Offline kron

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Re: Cat5, 6 extension cable
« Reply #14 on: August 07, 2013, 02:46:21 AM »
But I have found that in Cat7 cables each of the 4 twisted pair lines have individual shields. So the crosstalk should be quite small.

Hi. I don't know if you mean PIMF or something else. Some CAT6 cable have PIMF (pairs in metal foil) i.e. each twisted pairs are surrounded by metal foil(shielded) to minimize crosstalk
Daniel

Offline Rapp-Instruments

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Re: Cat5, 6 extension cable
« Reply #15 on: August 07, 2013, 04:18:09 AM »
Hi Daniel,

exactly!  I found this cables in EBay named Cat7 cables. I did not know the abbreviation PIMF

Thomas

Offline wreckreationaldivers

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Re: Cat5, 6 extension cable
« Reply #16 on: August 07, 2013, 09:57:15 PM »
PIMF, Pairs in Metal Foil


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