r/c sub hydrophones

[mylo]

Hey all,

I'm sure I read a post where someone was building functioning hydrophones for his sub that you could actually listen to stuff going on while on patrol (like the screws of an r/c destroyer). It was something relatively simple too, if I remember correct. Does anyone have any information on how to do that ?, or who that was who was doing that ? I did a search, came up with nadda.

Thanks,

Mylo

[Guest]

That'll be David Forrest (davy).

More

That'll be David Forrest (davy).

More information here-

http://rdforrest.mysite.wanadoo-members.co.uk/

I'm sure Dave will chip in when he reads this.

Andy

[raalst]

possible, granted,

but my bet

possible, granted,

but my bet is that Mylo saw an article by Mr. Merriman about putting a
small FM transmitter (see your local spyshop or radio shack
or the likes) into his WTC and tune into it with a normal FM radio.

Unfortunately I could not (re-)find it any more on his website.

[raalst]

this circuit, for example. 15

this circuit, for example. 15 bucks.

http://www.canakit.net/Default.asp?Contents=/Include/Template/MenuCat.asp&Main=http://www.canakit.net/Contents/Items/UK111.asp

[mylo]

Ronald, ......I'm not sure what

Ronald, ......I'm not sure what that is, or if it's what I'm talking about, but I'm guessing it's close. A 'mini-microphone' with it's signal transmitted FM ? ...maybe.

Mylo

[raalst]

yes, it is a microphone

yes, it is a microphone with transmitter. it transmits so you can receive
it with a normal FM radio (finding a portable FM radio these days, now
*that* is a challenge )

often sold as "spy" equipment (see "spy-shop") or built by starting
electronics students. The one in the link is a kit, so you have to solder
the components to the circuit board yourself.
Maybe radio shack or others sell pre-build ones ? dunno.
maybe you have a radio hobbyist or general electronics geek around
locally ?

If nothing else works out I'm quite willing to buy that kit (2 of 'm) put it together and mail one to you.

NB ! this is mono, so it's only for listening in, not for determining
direction.

one other NB ! these days, the video camera's come with sound.
Sure you want sound *only* ?

[mylo]

Ronald,

Yes, I'm interested in

Ronald,

Yes, I'm interested in sound only. I want a hydrophone station in my sub, just like it's full sized brother.

You're telling me that there is one that can determine direction as well ?

In the post I'm thinking of, the mic was mounted in a pill bottle or something in order to increase it's effectiveness. ....damn.....wish I could remember who was doing that.

Mylo

[Guest]

Some good information here-

http://sonar-fs.lboro.ac.uk/uag/product ...

Some good information here-

http://sonar-fs.lboro.ac.uk/uag/product ... phone.html

This is what Dave's system is based on, although he has made some modifications to make it more pondside friendly.

Andy

[tmsmalley]

One of our members has

One of our members has used this kit -

http://minute-man.com/acatalog/Transmitter_Kits.html

Probably won't be able to determine direction, even with a stereo transmitter, because the mics wouldn't be far enough apart. Water transmits sound a lot more efficiently than air. If you have ever stuck your head underwater when a motorboat passes by, you know that its impossible to tell where it is, just that it's getting nearer or farther.


Two-Stage FM Transmitter Kit
Philmore DATAKit # 80-320

A powerful little circuit with surprisingly good audio quality. Can transmit up to about 1/2 mile in open country. This is probably the most powerful FM band transmitter that you can legally purchase.


An electret microphone is included to add sensitvity. The kit includes a 4 AA battery holder to run the circuit at six volts, greatest output is 12 volts, but use 9 volts (or less) and a short antenna wire to stay legal.


Price: $11.79

[raalst]

microphone in pill bottle looks

microphone in pill bottle looks a bit like this

http://www.exfac.com/aussie_bray/hydro_dunking.htm

[anonymous]

Hi,

We do seem to be

Hi,

We do seem to be at cross purposes a little. Mylo obviously wants to put a hydrophone on his sub and then use a transmitter on his sub.

Which is fine but I personally don't see the point because it will only transmit when the sub is on the surface. Maybe you'd be better off putting the hydrophone in a model destroyer?

You will find that a hydrophone at the pondside will give much better resullts - no flow noises etc. You can hear everthing going on (and in!) the pond. And yes it can be used for rescue of subs equipped with my Pinger.

Yes FM transmitter circuits are plentiful the real need is a low cost hydrophone+ preamp circuit. (They typically cost $100's)
The Loughborough circuit is an excellent start but I found that I couldn't sell enough to sub enthusiasts to make it viable.

So Guys put your thinking caps on to get a low cost hydrophone and preamp. (BTW don't go for the one on Ebay by Mr Hulot - not sensitive enough.)

Davy

[mylo]

Davy,

What is a "hydrophone

Davy,

What is a "hydrophone at the pondside" ?

So, these FM transmitter circuits only transmit in air ? If so, good for destroyer, not good for sub, as Davy points out.

The construction of that dunking hydrophone seems more complicated than I remember this topic being discussed before. I need something smaller in diameter than 48mm. Neat little device though.

As for "low cost", I've given up on the thought that ANYTHING for this sub is going to be low cost. At this point, what's another few 100 bucks. *sigh*.

The research continues.

Many thanks, any input is appreciated.

Mylo

[raalst]

Hi Davy !

I'm fairly sure

Hi Davy !

I'm fairly sure the one in the merriman article worked from below the surface. cannot remember if it was FM or AM.

FM is about 80 Mhz I believe, could work from under the waves, and I don't know right away if an AM transmitter is using lower frq.

low cost hydrophone == normal electret mic with pre-amp kit (Conrad)
in a watertight enclosure (such as WTC or surface ship hull).

I built both the UK and aussie hydrophones and neither did well for me.
could be my skills. But as soon as you put a normal mic (in a plastic bag) in a bucket with water you get 10x as much sensitivity.

[mylo]

Ronald,

Yes, this is what

Ronald,

Yes, this is what I'm wondering....and I KNOW it was something simple like that that I read before (a year ago or so, maybe longer). It was just a 'normal' little mic, like the ones you can just clip to your shirt, very typical of what you can get for a small dictaphone. This little mic (4mm diameter maybe) was mounted in a small pill bottle (20mm diameter or so) to make it more effective somehow. This was then mounted to the inside of the hull. The whole thing worked while the sub was underwater. I just know I didn't dream this.

Mylo

[crazy ivan]

Mylo,
There was an article by

Mylo,
There was an article by Dave Merriman in The SubCommittee Report, issue 22 September 1995, titled "Passive Sonar for the R/C Submariner". Maybe you saw a reprint of that somewhere. As long as you're in a money spending frame of mind, maybe its time to order the Back Issue DVD and check it out.