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Author Topic: Worthwhile to make my new shack a faraday cage? How?  (Read 5580 times)
HS0ZIB
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« on: April 11, 2011, 06:11:56 PM »

Since my business as a hotel owner requires me to be up and about at all hours, I'm going to build a small shack at my Phuket hotel so that I can both enjoy my hobby whilst keeping an eye on the business.

The room will be constructed from 'breeze-block', which is the standard form of cheap construction in the tropics.  I was wondering whether it would benefit my noise level to construct this room with RFI shielding (chicken wire mesh) on all walls/floor/ceiling.  I could build a double-thickness wall with the mesh sandwiched in the middle.

Any thoughts?  Would the effort be worthwhile or should I just build a single skin room with no RFI shielding?

Simon
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W8JX
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« Reply #1 on: April 11, 2011, 06:57:05 PM »

Not sure what you think you might gain here. Noise you get is going to still get in thru antenna outside cage. Cages as normally for testing equipment in a interference free area or to prevent outside listeners from listening in via RFI leaks in computers and equipment.
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NA0AA
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« Reply #2 on: April 11, 2011, 09:03:41 PM »

As previously noted, the noise will come in on your antennas.  I think it would be a waste of effort. 

How about weather and dust proofing though?  I also might consider solid wall from a sound proofing point as well, if you are to operate late at night.

For what it's worth, I've seen only two Farady Cages in use in radio stations, both of them part of the KPH shore station, One is the control room at the transmitter site - and I'm sure it's to protect the instrmentation in the control room, maybe just to reduce RFI to the staff.

The other was the point-to-point room at the receive site, which has the very coolest copper-plated doors you have EVER seen - even the molding is laminated with sheet copper, finger stock for weatherstriping.  All the windows have copper mesh built in.

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KC8WUC
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« Reply #3 on: April 12, 2011, 05:39:51 AM »

While some stray RF may be picked up by an antenna, building a Faraday cage may cut down on RF from MRI's, CT scanners, transformers, X-ray equipment, and some other noxious sources.  In another lifetime, I worked in an office where a Faraday cage was installed in a waiting room and inner office to protect against eavesdropping.  This included use of copper wall paper (which was concealed by a more decorative and less conspicuous wall paper) and shielded doors and windows.  Holland Shielding manufactures Faraday cages and various materials for building Faraday cages.  Another product you might consider is use of QuietRF products, which includes an RF dampening drywall and plywood.  For sound, you might consider QuietRock and Quiet Putty, as well as closed cell spray foam between floor joists and wall studs (BASF and Dow make good products), as well as Sonex sound blocks.  All of these products will cost you a considerable outlay of money, so you will need to weigh the costs versus benefits carefully.

73,
Michael KC8WUC/WDE9344
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SV2CWR
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« Reply #4 on: April 12, 2011, 12:15:25 PM »

Hi Simon,

You can shield your shack from RF with a simpler method of painting it with a special paint. Check http://www.yshield.com/ for more info.

73/John/ SV2CWR
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N3JBH
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« Reply #5 on: April 12, 2011, 12:41:11 PM »

I would think that most of your RF will be picked up or transmitted by the antenna. That sort of makes the whole point of shielding the station  a moot point. and secondly it wont stop your customers  from getting Rf....
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KD8MJR
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« Reply #6 on: April 13, 2011, 01:25:19 AM »

Total waste of money. Your cash Is better saved for use on the Antenna or Radio.
That's the way to get rid of more noise.
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HS0ZIB
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« Reply #7 on: April 14, 2011, 04:04:04 PM »

Perhaps I should have made my OP more clear. My idea to shield the shack was proposed if this MAY reduce any RF from nearby air-con compressors, computers etc.  Of course, the emphasis is on the word 'may', since clearly my antenna will also pick-up such radiation.

But if by sensible use of shielding materials and mains filters, I can reduce (by any small amount) my local RFI levels, then that will be a benefit

Simon
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K1CJS
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« Reply #8 on: April 16, 2011, 07:22:11 AM »

To answer your original question with one word--no.  It wouldn't be worth it.  You would need a solid metallic sheet with no gaps or seams to accomplish that, and every electrical wire--and antenna co-ax, for that matter--that penetrates that 'cage' is just another point that RF can penetrate.

As others have said, better to use your money on quality antennas and co-ax and noise suppressors than to try to accomplish what you want by building a faraday cage.
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AF6AU
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« Reply #9 on: April 19, 2011, 09:38:36 AM »

You hit a specialty of mine. You have to consider the frequencies you want to attenuate and how much attenuation you need. A good Faraday shield is multiple layers, continuous connection, low resistance materials. The "chicken wire" mesh would have to be soldered in many places, then painted to prevent oxidation.

A lab Faraday shield is often multiple layers, a iron mesh to shield off frequencies below 20KHz, and copper, soldered or brazed, on a inner layer sheeting to shield off RF. Now the "mesh" is effective for frequencies where their wavelength is about 20 times the size of your holes and greater. The door would need finger springs and be grounded all the way around.

You would need brute force filtering of the power mains coming inside, grounded to the shield at the point of entry. Lighting best be done with incandescent lamps or LED's, as they not emit much RF, but the power will also need filtering. Coax line shields would need to be grounded at the cage as well, or the outer shield can conduct all sorts of garbage RF inside as well.

Now consider a well built transceiver, connected with good coax lines with clean connectors, using (close to the transceiver) line filtering, and your external lines like speaker, data, microphone, CW key, you have achieved your Faraday shield in miniature form. Unless you are running open chassis doing sensitive repairs or something, you don't need Faraday or RF attenuating construction.

Properly done, the only point of entry for RF into a modern transceiver should be the inside conductor of the antenna coax cable. Forget the cage, properly treat all of the cables connected to the rig, and ground it.
AF6AU
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