Tethered cameras?

[Unregistered]

Strictly speaking this isn't a sonar question, but since I'm thinking of it as an adjunct to sonar, I hope you all won't mind my posting it here.

Let's say I get one of the affordable side-scan sonar systems and locate some promising-looking targets. Besides getting a diver to jump in and check it out, it seems as though it would be very handy to have a tethered camera that I could lower down for a closer look. Is there anything at the bargain-basement end of the price spectrum that you all could recommend?

[Glennk]

Just build you a housing that dont leak under pressure of the water. I can send you a drawing of one design you can use, and then you can use almost any camera that is availiable. I would recomend a good BW camera, of 0.00x to 0.02 lux. Any higher lux value than this, you yould probably need lights, depending on the water clarity.
Artificial lights are no-no, as it reflects light in the particles in the water, and can blind the camera. So if you can go without lights, dont use them!

Glenn

[Francisco Xavier]

Hi Glennk,
I build my own camera using cheap BW CCD, 80 meters flexible coaxial cable and a common BW tv.
I machine (from nylon torus and plexiglas) my waterproof housing (was expensive and time consuming), but you can buy cheap underwater light (for diving) and assemble one rear waterproof cable strangler.
The Aquiles heel is to send the 12 V cc to CCD and receive the 3 MHz band video signal back ON same coax wire!
After using a unstable passive circuit built my own, now I use the Coax Video Transmitter/Receiver - V-VL2122 from:
http://www.ktechuk.com/ktprod/ktmars...ideo_range.htm
I am diver (instructor) but my underwater video is a great help !!!

Good luck

[Glennk]

12VDC and vpp signal for video on same coax can make a hassle.
But if you use good quality 3-wire cable, you can run 12V+, Video return and common shield/12V- on the 3 wires.
We use this on most of our equipment for commercial diving.
On other systems we use a combined cable containing a mini-coax for the video, and a pair of current supply wires for the 12V.

[Unregistered]

Glennk,
I have used a 3-separeted wire before and have a decente picture. But
- the cable was some rigid/thick and more susceptible at stream drag
- as each wire/conductor is not coaxial the 80 meters coil change a lot the
inductance and I have to add a passive circuit (indutance/capacitance -
resistor) to tune the signal (and vertical sinc) on the tv!
After had tuned if I have to uncoil some meters more I had to tune the indutance again. It was a lot annoying !!!
Believe me the circuit V-VL2122 is a great improvement on picture quality and less work to operate the camera.

Greetings

[Glennk]

I totally agree with you!
The best is to use a device like you do, or use a video-amplifier. But still, I think the sollution that u use is the best if you do not have access to a cable as e.g. the combined mini-coax/current cable.

Glenn

[UWLocator]

I use two of the really cheap cameras you can pick up on eBay for about $100. One I use just like it came in areas where the current is not bad. The other is mounted in a housing made of 2" and 4" PVC pipe and filled with 75 lbs of lead shot to drop down even in current. That one the camera is mounted to look straight down and I added a ring of 25 superbrite led's to help light up the area under it.

I also have a pillow that attaches to the drop camera and can be filled with clean water to sit down on small objects and help see them. It works fairly well if the bottom is not too soft and the water is turbid.

Rip

[Seeker]

12VDC and vpp signal for video on same coax can make a hassle.
But if you use good quality 3-wire cable, you can run 12V+, Video return and common shield/12V- on the 3 wires.
We use this on most of our equipment for commercial diving.
On other systems we use a combined cable containing a mini-coax for the video, and a pair of current supply wires for the 12V.

Hi ,
If you mast use only coax-cable, there no problem to send TV and DC in one cable.
You can separate signal and supply with simple schematic.This I check on 100m RG-59(75 Om)

[Francisco Xavier]

Hi Seeker,
I have used a schematic like you publish just a passive filter (from http://www.qsl.net/sm7ovk/schema_biastee.jpg):

With this circuit I never could filter the video signal without degrading it, because the video signal is a frequency chanel from some fews Hz to 3 MHz.
It works fine if you have a strait band frequency far from the cc current.
Other solution is using active filters like a synthesized inductor: http://www.edn.com/archives/1997/092597/20di_01.htm but I could not find the ICs on the market here in Portugal (if know some common equivalent ICs please inform me).
Does your scheme works fine with video signal without distortion?

Greetings

[Seeker]

Hi Seeker,
I have used a schematic like you publish just a passive filter (from http://www.qsl.net/sm7ovk/schema_biastee.jpg):

With this circuit I never could filter the video signal without degrading it, because the video signal is a frequency chanel from some fews Hz to 3 MHz.
It works fine if you have a strait band frequency far from the cc current.
Other solution is using active filters like a synthesized inductor: http://www.edn.com/archives/1997/092597/20di_01.htm but I could not find the ICs on the market here in Portugal (if know some common equivalent ICs please inform me).
Does your scheme works fine with video signal without distortion?

Greetings

Hi,
the schematic from http://www.qsl.net/sm7ovk/schema_biastee.jpg isn't good for TV band.It is good for RF.
In my schematic ,I use big inductance(500mH) to stop all AC component and schematic give good results.
Of course , there is better schematic with RF and DC-DC module for lines to 300-500m, but they are more complicated. If you need I will send you schematic.

[Glennk]

Hi,
the schematic from http://www.qsl.net/sm7ovk/schema_biastee.jpg isn't good for TV band.It is good for RF.
In my schematic ,I use big inductance(500mH) to stop all AC component and schematic give good results.
Of course , there is better schematic with RF and DC-DC module for lines to 300-500m, but they are more complicated. If you need I will send you schematic.

It would be very nice of you if you'd like to share the schematics with us.

Glenn

[Seeker]

It would be very nice of you if you'd like to share the schematics with us.

Glenn

Hi Glenn,
this schematic is commercial development, I can't give it all. But I will mention how to do easy version. You need common TVsender at 1-4 TVchannel, UPS 110/220V 600VA with 12V accumulator, pulse power supply for 110/220V for 12V/ 2A or more, TV receiver 14"(with pulse power supply) and some electronics parts.
For CCIRT standart:
First mast to stabilize the frequency of sender by input quartz at 49,75 ; 59,25 or 77,25 MHz and increase output power on 20dB by 1 transistor.This sender will send full colour TV spectrum.
Look at the picture.If you have any questions, I am here.