rf shielding spray

[dalbert02]

I just bought some MG Chemical Super Shielding spray. Any one every try this stuff? With the close proximety of recievers, GPS, video transmitters, radio modems, etc. I am hopeful that this will help get rid of some of the interfernce.
-dave

http://www.mgchemicals.com/images/product/841.GIF

[workshop]

Friends don't let friends use shielding spray!!! :eek:

Dave, seriously... I'm not sure if you're joking and I don't get it... :o

Come on... we can work out your interference problems without resorting to suicide by spray can! :rolleyes:

Jeff

[Mark Harris]

This stuff works great when you put your GPS unit and rx antenna in it!





(joking)

[Wulffy]

Tough crowd to get a straight answer out of, eh? :p

Sorry, never used it, but nice to know that stufdt like that exists...

If you do end up using it, please advise how it turns out for you.

Thanks, in advance!

-t

[workshop]

The stuff will get everywhere, flake off over time and generally make all your microelectronics fail because of shorts as it works into your enclosures.

Buy some copper foil (I use the adhesive backed kind from Datak) and make some balsa RF enclosures. Optoisolate video from RC control and route your TX antennae with a ground plane and away from the rest of the plane.

Ground everything to the negative terminal of your RX battery.

Jeff

[dalbert02]

Well, I did a test spray on the cardboard box it came in. The packing tape got sprayed as well. It is mat gray in color. I bent the tape back and forth several times and it didn't flake, but who knows over time.

I currently have my servos wrapped in copper tape and all the electronics spread out as far as possible. 2.4Ghz video Tx mid plane, video TX antenna in the tail, GPS and OSD in the nose, FMA Rx in the center, Rx antenna wire down one wing and RX counter poise antenna down the other, FMA opto-isolators, AP-4 autopilot, seperate batteries for everything. Using the RSSI out displayed on the OSD I can see that the range is reduced when everything is powered up. All servo wires are twisted. Everything grounds at one point to eliminate ground loops. Any thoughts on shielded servo wires, like microphone cable? Any ideas appreciated.
Thanks,
-dave

PS As a side note, I have noticed that the inside of David Clark headphone/mic connector boxes are covered in a copper color metalic flake. http://www.davidclark.com/IntercomSys/3800mod.htm

[workshop]

Dave,

Think of that spray on shield stuff like JB Weld… It is handy for a spot repair but no substitute for real welding. Also the binders do age… Check out www.teslacoil.com - I spend my days chasing the RF monkey.

I’m reasoning that your transmitters are 1W or below. It seems like you’re doing everything right; too right. You shouldn’t have to shield your servo wires (twist, yes) or your servos to limit interference. From your description, my first thought is the header circuitry of your RC RX.

For grins, swap out what you have for a JR RX (Futaba makes great gear too but there are 3.3v logic level shifting issues that make you want to avoid this brand just for the test) and see what happens to your symptoms. I have a seven channel that you can borrow for the test (you’ll just have to buy a crystal unless you’re #58 on 72MHz).

Have any photos?…

Jeff

p.s. re-reading your post… Why the distance between the VidTX and the Antennae? Can you describe the counterpoise?…(ground plane or antennae wire?)

[ImaBiggles]

The stuff will get everywhere, flake off over time and generally make all your microelectronics fail because of shorts as it works into your enclosures.

Buy some copper foil (I use the adhesive backed kind from Datak) and make some balsa RF enclosures. Optoisolate video from RC control and route your TX antennae with a ground plane and away from the rest of the plane.

Ground everything to the negative terminal of your RX battery.

Jeff

RF Shielding will not work in most if not all cases as the RX antennae has to be exposed. Build a faraday cage and stick your RX in there - sure no interference, no signal from the TX also. THe only think you can do its get a good double conversion RX, a berg, or spectrum. Ive only run into EMF when using crappy electronics. I have a BEC that I bet would shoot down a plane if I put a antennae on the ground plate. Its currently in use powering a LED strip for grins.

For the vid tx, I would strongly suggest putting a ceramic cap across the power input - they are VERY prone to issues with voltage ripple.

[ImaBiggles]

PS As a side note, I have noticed that the inside of David Clark headphone/mic connector boxes are covered in a copper color metalic flake. http://www.davidclark.com/IntercomSys/3800mod.htm
Audiophiles will buy any kind of stupid expensive stuff if someone tells them it improves sound. My brother had a zillion strand 4 or 6 guage speaker wire on his expensive tower speakers (I think he said $20 a foot). One time when I was over, I change it to typical 12 awg speaker wire at $0.50 a foot. It was two weeks later when I stopped by next and he couldnt tell the difference, despite listening to music <6 hours a day (works at home).

As a result, he had to buy the beer.

[dalbert02]

Thank you Jeff, Ima, et al,

Sorry for the great delay in responding, been working way too much! Attached are some pics of my installation. Harsh criticism welcome. :)

-dave

[Mark Harris]

Get a new GPS... that thing is massive and heavy looking.

[dalbert02]

Wow, really, I thought the Geko 201 was one of the lightest. Can you recommend one that has NEMA out for the waypoints?
Thanks! On a side note, I did take the AAA batteries out and used a Dimension Engineering 3.3v switching regulator on it...
-dave

[workshop]

As externals go the Geko201 is one of the lightest... Not the source of the RF problem though... What about the unshielded electronics under the canopy? Where is your antennae connector (e.g. RF Module)? Why the patch antennae on the plane? Do you have radiation patterns for that antenna (manufactures literature)? Can you swap for a rubber ducky dipole? IMO, the RX is still the weakest link in your system. What do you think about swapping it out for a test?

Jeff

[_helitron_]

Good idea workshop but the problem is, Dave cannot simply remove the Rx without removing the complete IR-stabilizer. The FS-8 Rx is an integral part of the FMA FS-8CPI co-pilot. I can only speak of my own experiences several month ago with my Cularis. Had also a FS-8 co-pilot in use but had without any other electronics on board massive range problems. Normally my Futaba FC-28 has a range of 2 km for sure but with the FS-8 I had already glitches only 200 m away in a height of about 20 m. Tried a lot of things but no chance, must remove the FS-8. I replaced it with an AP2000i IR-stabilizer from SpartanRC in UK (advantage: the FMA X-Y IR-sensor is usable for the AP2000i) and one of my good old Futaba PCM Rx. Since then I flew away more than 1000 m without any failsafe so far. I bet it's the FS-8 Rx.

Cheers,

//Erwin

[workshop]

There IS a stand-alone FS8 IR unit for use with other receivers but we are adding to Dave's bill. However, what is the price for success?... :rolleyes:

Jeff

[_helitron_]

Sorry Jeff but the "FS-8" co-pilot has always a receiver included (FS-8 = receiver), I assume you mean the FMA CPD4 co-pilot, that's a stand alone IR-stabilizer without a Rx.

//Erwin

[workshop]

Right you are sir! I have two... They work well.

[dalbert02]

As externals go the Geko201 is one of the lightest... Not the source of the RF problem though... What about the unshielded electronics under the canopy? Where is your antennae connector (e.g. RF Module)? Why the patch antennae on the plane? Do you have radiation patterns for that antenna (manufactures literature)? Can you swap for a rubber ducky dipole? IMO, the RX is still the weakest link in your system. What do you think about swapping it out for a test?

Jeff


Hi Jeff,
The electronics under the canopy is the Inspire (previously known as Geko) OSD board from RC-CAM. The underside of the board has a plastic insulator and then a thin metal plate. Do you think it would be wise to put a plate on the top as well (like a sandwich) or must I build a sealed faraday type cage?

The patch antenna is one that was sold by black widow. I thought it would direct more of the RF energy downward then a dipole. I can try a dipole too just to make sure it isn't causing any grief. The more I learn from everyone the more I think the FMA reciever may be the problem. It seems like quite a few have had problems with it. I guess I should just change it for a good non PCM Rx. Does anyone know if the JR 50Mhz Rx's will work with a Futaba Tx as at 50Mhz they are the same shift?

Thanks again for all your assistance. :)

-dave

Antenna specs:
Frequency *824-896, 890-940,806-866, 2400-2500 MHz
Element Type Edge Slot Radiator
Polarization Vertical
Gain (min) +3 dBi
Azimuth Omnidirectional
Elevation Cosine Shaped Monopole
VSWR <1.5:1 @ resonance 2:1
Impedance 50 Ohm
Power 100 Watts
Cable Type RG-58U

[MGguy]

Hey guys,

I found this thread on our hit report today so I thought I'd check it out.

I'm the guy that formulated our 841 Super Shield Conductive Nickel coating, so anything you want to know, just ask.

The product is pretty much just high purity conductive nickel flake in an acrylic lacquer formula that was originally intended for use on wood.

As to what is superior between this coating and a conductive tape, well I think tape is less costly but more of a pain to apply properly.

Also, copper tape is of course going to block different frequencies then a nickel coating. Each metal has it's own absorption profile and most products made for shielding should have a graph available that shows which frequencies the product is good at shielding. Certain metals and pigments are better then others certain applications. It depends what frequencies are bothering your device (I'd suggest not trusting products that list a shielding effectiveness in dB without listing a frequency).

We have a graph that compares the effectiveness of our paint with different pigments here:
http://www.mgchemicals.com/products/popup/graph-841shield.html

Nickel pigments have an advantage over silver and copper pigments in that nickel blocks both the magnetic and electrical components of EM radiation, whereas the others only block the electrical component.

Where this product excels is if you have a plastic electronic enclosure. You just spray the inside and it's good to go in 10 minutes.

A lot of times companies develop a product and are just about ready to go to market and then realize at the last moment that there's such a thing as FCC standards and they have to shield their product before they can sell it. This product is really good for that sort of situation, because they can just spray the insides of the enclosures and they are good for their first few production runs, which gives them time to come up with a less costly alternative, like metal shells or mesh.

We sell a lot of this product in liquid form for large production runs in China, but the aerosol can does very well in North America, because it allows small manufacturers and hobbyists to be able to apply the paint without having to obtain proper spray equipment. I'm not sure if anyone else is offering a spray in aerosol form these days or not. GC used to sell a carbon based one in aerosol, but I think they deleted it. I'm not sure about that though.

This product is used on the inside of a lot of cell phones and pda's.

As for it flaking and dropping into your circuit, I've never ever heard of that happening. I'm sure someone would have called me trying to get money for killing their expensive electronics if that ever happened, and nobody has tried that yet.

The product is UL approved for adhesion to ABS plastic and polycarbonate plastic at both hot and cold temperatures, and part of that test includes abrasion tests.

The product will not adhere to glass, and will have issues if you are trying to apply to porous surfaces, or very chemically resistant surfaces. It will adhere to metal, wood, and plastics.

We use this same acrylic base for our Acrylic Conformal Coating, because it's super tough, durable, and moisture resistant.

That said, most of your tougher acrylics require Toluene in the formula in order to get the resin to break down, and our product is no different. Toluene is a prop 65 chemical, "known to the state of California to be reproductively toxic", so you want excellent ventilation when spraying this product. If you just have one device to shield, just spray it outside, stand upwind, and you will be fine. Just don't spray it in your eye :)

When working in an enclosed space, a half mask respirator with an organic vapor cartridge will control the hazard, or a good fume hood is another option.

One important point about this product is that when you are done using it for the day, you must turn the can upside down and press the button, spraying until you just get clear propellant coming out ( this will only take a second). This clears the paint out of the valve. If you don't do that, then the nickel flakes can possibly jam the valve open, and over night the rest of the paint might bubble out of the can.

Howard Clark
President
MG Chemicals

[dalbert02]

Thank you Mr. Clark. Your input is greatly welcomed and appreciated!
-dave

[workshop]

Way to go Howard in the positive PR department.

My comment on flaking was based on experience I have with other conductive coatings not your product in particular. It is good to know that your spray is formulated to resist breakdown from binder failure (age, UV, vibration, etc.). Since your product is suitable for wood, perhaps I’ll test it out on some of my balsa wood R.F. enclosures (I usually used 1/32” PCB or copper clad balsa wood).

I own a special effects manufacturing company called kVA Effects (www.teslacoil.com). We have the need from time to time to make various objects with compound curves conductive to high voltage (750,000V and above). Your spray may work for us for that purpose.

If you want, I can copy your post to the Tesla Coil Mailing List so high voltage professionals and hobbyists can try your RF Spray too.

Jeff W. Parisse
kVA Effects
www.teslacoil.com

[MGguy]

"If you want, I can copy your post to the Tesla Coil Mailing List so high voltage professionals and hobbyists can try your RF Spray too."

Please do, and thanks for the nice comments =)

[ImaBiggles]

That said, most of your tougher acrylics require Toluene in the formula in order to get the resin to break down, and our product is no different. Toluene is a prop 65 chemical, "known to the state of California to be reproductively toxic", so you want excellent ventilation when spraying this product. If you just have one device to shield, just spray it outside, stand upwind, and you will be fine. Just don't spray it in your eye :)

When working in an enclosed space, a half mask respirator with an organic vapor cartridge will control the hazard, or a good fume hood is another option.

. . . .


Howard Clark
President
MG Chemicals

Mr. Clark,
As one who works in chemical manufacturing, I commend you on taking the time to add the safety concerns and PPE recommendations to your info. Many times in such an informal communication they are not mentioned. 'Safety Culture' is all to often just a cache phase for corporations. In reading your post, I get the strong feeling that safety is a real priority at your facility. I bet your OSHA recordables are pretty darn low.