Parabolic dish and microphone

[NorthWind]

22 minutes ago, wiiawiwb said:

Northwind...that looks great and thank you for being so thoughtful.  Forgive my greenhorn handyman questions because I'm not handy at all:

 

1) How did you attach the 3/4" coupler on the inside part of the dish to the pipe coming through the hole?

2) When I found squirrel baffles that I liked, the hole in the dish would not snugly accommodate any size pvc pipe I could find in Home Depot.  How would I go about filling the space and fitting the pvc pipe snugly so the dish doesn't slide around?

 

 

Between the elbow and the coupler is just a short section (about an inch and a quarter long) of 3/4" pipe. In the photo, you can see it sticking out of the elbow. Just slide it through the hole in the dish, and slide the coupler on the pipe. Easy peasy. The hole in the dish is just large enough to accommodate the pipe, but not the coupler or elbow. The coupler is female on both sides. As is the elbow. The cap is female, too.  PVC cement.

 

The squirrel baffle hole, not sure. Maybe someone else would have an idea on that.

 

Here's a YouTube video on a guy that made one...

 

 

 

and the squirrel baffle mic plans are here:

 

https://makezine.com/projects/squirrel-baffle-spy-microphone/ 

 

They both do it a little differently. Maybe that'll help. 

 

 

Edited February 18, 2020 by NorthWind
Added a little more detail.

[SWWASAS]

17 hours ago, NorthWind said:

 

 

Yeah, it's not a true parabola, but it is close enough for now, anyway. I used a laser and determined the height for the mics on the kit. I am going to paint this thing camo, I think. Or just a flat green / brown.  Depends on what I can scrounge up. I want sound reflected, not light.

 

And yes, I know about the dangers of solar rays! I got a Fresnel lens from an old projection TV (it's about 3 x 4 feet) and mounted that in a frame. When I place that beast in the sun and remove the black cloth I have covering it, it will melt and boil a handful of pennies in a matter of seconds. And I mean totally vaporize them. That heat is so high it is scary, and you have to wear welding glasses because the light is so intense. I can melt range lead with it.

 

Thanks for the warning, @SWWASAS

 

Wow that Fresnel lens would make a good solar powered steam engine source of electricity.    At those high temperatures you might need to use some liquid metal as a transfer medium to heat water in a boiler.       There are also thermoelectric devices that can directly change heat into electricity.       But if it melts pennys it might produce too much heat for those devices.    Just curious what the brand of projection TV was.    I would like to find one of those big lenses.   You never know when you need to make a death ray.   

 

Painting the dish eliminates the problem  of burning stuff accidently.      The wave length of sound is so long paint would do nothing to mess up the focus like it would to light.   

[NorthWind]

3 hours ago, SWWASAS said:

Wow that Fresnel lens would make a good solar powered steam engine source of electricity.    At those high temperatures you might need to use some liquid metal as a transfer medium to heat water in a boiler.       There are also thermoelectric devices that can directly change heat into electricity.       But if it melts pennys it might produce too much heat for those devices.    Just curious what the brand of projection TV was.    I would like to find one of those big lenses.   You never know when you need to make a death ray.   

 

Painting the dish eliminates the problem  of burning stuff accidently.      The wave length of sound is so long paint would do nothing to mess up the focus like it would to light.   

 

 

I have no idea the brand. But you can find these things free, you just have to put in the work and remove the lens then junk the rest. The lens is usually covered by a thin plastic sheet for protection. 

 

https://seattle.craigslist.org/skc/zip/d/federal-way-52tv/7076045276.html

 

Here's one n CL for free in the Seattle area. Take a look on CL in your area if you are not in Seattle. They are kind of fun to play with. Just be careful - they can be quite dangerous.

 

Edited February 18, 2020 by NorthWind
Added a little more detail.

[MIB]

For a parabolic, I would look at Kryder's kxpd2.   The recording setup is just a little more sophisticated (ie complicated) than I'm hoping for.   Pro gear rather than amateur, maybe.

 

MIB

[BlackRockBigfoot]

On 2/17/2020 at 5:57 PM, NorthWind said:

 

 

The stainless bowl is a round bottomed mixing bowl from Ikea.  I drilled and then cut a hole in the bottom. I could have used a squirrel baffle from Home Depot, but I got the bowl free and after buying a FLIR, I am kind of broke for a while.

 

The PVC s 3/4". In the end cap, I have epoxied a connecting nut that is made for all-thread rod, so I can later mount this on a tripod if I want to (same threads). On the inside is a 3/4" coupler, that has a slot in it for the Velleman Super Stereo Ear kit that I soldered up (that kit was less than fifteen dollars and took about an hour to build.)

 

I drilled a hole in the elbow so I can run wires, battery and audio (either headphones or to an FM transmitter which I haven't built yet).  It's still a work in progress. I will paint it all when I get it together.

 

I hope that's helpful for you, @wiiawiwb

I missed this when you first posted it.  Well done!

[wiiawiwb]

Great job by NW. Pretty amazing how clever some people can be. A friend of mine can look at anything and devise a way to build it or improve on it. Me, I'm totally useless when it comes to being handy. It's pretty sad but the only tool in my toolbox is my checkbook.

 

By the way BRB, have you used your Wildtronics setup much and how do you like it?

Edited March 21, 2022 by wiiawiwb

[BlackRockBigfoot]

5 hours ago, wiiawiwb said:

Great job by NW. Pretty amazing how clever some people can be. A friend of mine can look at anything and devise a way to build it or improve on it. Me, I'm totally useless when it comes to being handy. It's pretty sad but the only tool in my toolbox is my checkbook.

 

By the way BRB, have you used your Wildtronics setup much and how do you like it?

The parabolic is great.  We need to try a different tripod, because it picks up every little squeak that the tripod makes when scanning from side to side.  
 

We haven’t used it much lately, due to the fact that the area that we are mostly in right now seems to go completely dead the moment we set up stationary and put up all of the big equipment.  As small as it is, it’s too clumsy to really use on foot in thicker woods.  
 

All in all, I am happy with its performance.  It works much better than I expected given its small size 

[SasquatchPA]

15 minutes ago, BlackRockBigfoot said:

The parabolic is great.  We need to try a different tripod, because it picks up every little squeak that the tripod makes when scanning from side to side.  
 

We haven’t used it much lately, due to the fact that the area that we are mostly in right now seems to go completely dead the moment we set up stationary and put up all of the big equipment.  As small as it is, it’s too clumsy to really use on foot in thicker woods.  
 

All in all, I am happy with its performance.  It works much better than I expected given its small size 

One thing that can help tame noise is to “paint” the very edge of the dish with plastisol. In helps dampen the standing waves on the metal dish. This in turn keeps the metal dish from acting like a bell.

[BlackRockBigfoot]

Just now, SasquatchPA said:

One thing that can help tame noise is to “paint” the very edge of the dish with plastisol. In helps dampen the standing waves on the metal dish. This in turn keeps the metal dish from acting like a bell.

the parabolic just squeaks loudly when you pan horizontally.  Not a problem with the thermals and nv that we usually use on those tripods. 

[SWWASAS]

Word of caution to those messing with parabolic dishes.      I nearly burned my truck up because I was not careful loading the dish and allowed the sun to shine into the dish.   I smelled something burning and the dish had focused the sun onto my passenger seat which was just starting to burn.     Safety would dictate painting the dish a dark color or olive drab to prevent it from lighting things on fire.     I hate to do that to the dish because it is such a good solar oven too.     The microphone is in danger if you point a dish towards the sun.   A few seconds and your microphone would be toast.     Dishes that work well are not exactly hiking portable and relay heavily on electrics to amplify the sound with smaller dishes.      Another option that may be a bit more portable is a series of aluminum or plastic tubes that are cut to tune different frequencies or harmonics of frequencies.     You arrange them bundled together in a group sort of like a minigun,    and put the base of each tube in a sealed fixture with a microphone.      Plastic tubes would be lighter than aluminum.       You point the minigun looking thing in the direction you want to sample.    When sound that is a harmonic of the tube hits the end,   a standing wave forms in the tube.       A big church pipe organ uses this standing wave method to produce their sounds.     I would concentrate on lower frequencies to pick up BF footfalls and growls.   Movie companies use this kind of highly directional mikes.      Get out your old physics book or look on line to find formulas to determine length of the tubes.     

 

   If you want to produce infrasound,   a large diameter PVC pipe of the right combination of diameter and length with a speaker mounted at one end would produce resonance sound in the 5 to 15 HZ range which a BF laid on me.      Not sure what that would do other than probably draw in BF in the area to see what is going on.     When my research area was active I saw no need to do anything to draw them in.     They found me.      Now that I have lost contact with that group,  I am looking at something to draw them in again.   

[Catmandoo]

2 hours ago, SWWASAS said:

 A big church pipe organ uses this standing wave method to produce their sounds.

The size of the organ is everything.

In reading the 'minigun' description, looks to me as bundled 'shotgun mics' that have selective frequency response. Recording would be interesting. Systematically switch from tube to tube or send each signal to a multi-channel recorder. Tube to tube resonance is something to think about.

 

Infrasound projection: corner horns. You have them and I have plans for SpeakerLab corner horns. Big, heavy and not really suited for outdoor work but they would rock the whole forest. Rock on.