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Author Topic: Transparent Glowbug Chassis/Cabinet  (Read 3483 times)
KB1WSY
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Posts: 812




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« on: February 25, 2012, 01:31:05 AM »

Does anyone have experience building transparent chassis or cabinets? Unlike 40 years ago when I liked the idea of putting all my tube gear in a nice closed cabinet (with holes only for ventilation) I am thinking of experimenting with fully or partially transparent gear. This raises obvious challenges with (1) which materials, (2) how to work them, (3) adequate shielding and (4) last but not least, cost. I have done a lot of Internet research on this and found some people who built such gear, mainly in the computer gaming community.

The coolest option is shielded glass. A number of companies offer this, including Pilkington and Tempest. This material is actually entirely transparent, in other words it does not look like a "grille" and has the appearance of regular or tinted glass. Actually working this material -- cutting it or drilling it -- would appear to be a major issue although presumably commercial manufacturers of transparent gear have coped with it. It looks like pre-built cabinets are available and in fact the cabinet is an easier issue than the chassis since it doesn't necessarily need to have new holes drilled in it. All of the "shielded glass" products seem *very* expensive however and often difficult to buy in small quantities.

Another route is to use some kind of cheaper transparent material (plain glass or perspex) and line it with adhesive shielding. A number of vendors offer this shielding. Don't know how easy this would be, in terms of avoiding air bubbles, getting a proper wrap, connecting the shields to ground, etc.

Some manufacturers offer relatively affordable prebuilt transparent shielded enclosures for the hobbyist, again, mainly from the computer gaming community. Haven't found a "ham" form factor though.

Seems to me that theoretically all of these options should offer adequate shielding (Faraday Cage) and the manufacturers seem to back this with reams of numerical RF specs.

I have found quite a few examples of people who actually built transparent radios and posted the pictures on websites, but mainly solid state and not hams. Am looking for an affordable solution although I recognize this is likely to be more expensive than a traditional aluminum chassis. Indeed it would probably be wise to prototype the gear on a traditional chassis before trying to implement the transparent version.

The only actual examples I can think of from the tube era of ham radio are (a) the frequent use, back then, of so called "cane metal" which presumably was a good shield otherwise it wouldn't have been so widely used, (b) the perforated grilles used on a lot of tube equipment including 21st century audio amplifiers that are designed to "show off" the glowing tubes.

One random thought: every consumer microwave oven has a glass door with a perforated metal shield. So that stuff must be produced in massive quantities and the shielding must be reasonably impressive. I even wondered whether finding junked microwave ovens and turning them into cabinets might be one cheap route.

Just kicking this one out there in case people have ideas or practical experience with this. Don't want to reinvent the wheel. Apologies for the long post but I wanted y'all to know what I've already investigated, to reduce idea duplication in the replies....
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W7ETA
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« Reply #1 on: February 25, 2012, 08:03:47 PM »

This link might provide useful information:  AudioKarma, DIY, sticky building clear cabinets

http://www.audiokarma.org/forums/showthread.php?t=149130

73
Bob

Oh. Ham radio led me into tubed audio gear, especially gear with schematics I could follow, tubed gear.
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N3QE
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« Reply #2 on: February 26, 2012, 11:27:46 AM »

I use transparent polycarbonate for coil forms, insulators, antenna insulators, plug in assemblies, etc.

It has the transparent thing going on but way above that, polycarbonate is a joy to work with and has excellent electrical properties. Unlike acrylic/plexiglass, this polycarbonate stuff is almost uncrackable. It does not shatter on being drilled, cut, etc in the same way acrylic tends to if not done with care or the right tooling.
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KB1WSY
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« Reply #3 on: February 27, 2012, 08:48:42 AM »

Thank you for the replies, very interesting.

Meanwhile I have an update. I have gotten in touch with a company that makes clear *glass* that is specially treated to give 60db RF attenuation, and also have the contact details for some people who might help with supplying custom cabinets or even chassis made with this material. My guess is it will be way beyond my budget and/or impractical for one reason or another ... we'll see. Plus, getting this stuff custom-manufactured by someone else sorta clashes with my homebrew ethos. Not yet clear whether there is any way for a hobbyist to build stuff from the raw material. Will keep you posted.

Mind you, if this stuff actually is usable, it would be an extremely rigid material for things like VFOs and tuned circuits on receivers, adding substantial stability one would think.

73 de Martin
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WX7G
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« Reply #4 on: February 27, 2012, 06:23:18 PM »

The style for modern tube audio amps is tubes and transformers on top of a nice chassis. Ham gear used to be made like this too. I see no hard reason to shield a transmitter or a receiver if the only thing exposed are the tubes.
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W7ETA
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« Reply #5 on: February 28, 2012, 05:59:44 AM »

Sounds like great stuff Martin.

I'm guessing a not so great price goes with it.

73
Bob

PS: With SMT, maybe you can built a rig in a bottle??
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KB1WSY
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« Reply #6 on: February 28, 2012, 07:54:34 AM »

Indeed, shielding usually isn't needed, although obviously there are sub-circuits that require it. Actually I want to be able to admire, not just the above-chassis tubes, but all the components and point to point wiring that are usually concealed under the chassis. If you told me this is all a bit mad, I would heartily agree with you, but since it's "just" a hobby I am allowed to be a bit eccentric, don't you think? Especially if I insist on using obsolete components in the first place.... I'm a sucker for science museums and their transparent displays that show you "the works" inside the equipment. It would be fun to have a little bit of that at home. A good conversation piece with non-hams, too. Plus, a way to build "period" equipment from the 1950s and 60s that wouldn't just be a replica of what was described in the ARRL manuals or QST but actually a new twist on it, esthetically speaking.
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